FAQ: Icom IC-746 HF/VHF Transceiver
Coordinator: Dana Hoggatt
kb9sss@arrl.net
Copyright (c) 2001,2002 by Dana Hoggatt, all rights reserved.
==============================
Recent Changes
10.22.2002 Minor addition to band edge beeps
10.20.2002 More info on ignition noise
10.11.2002 Updated info on Icom HF net
10.08.2002 Added Q/A about loose tuning shaft
10.07.2002 Added Q/A about 2m S-meter readings
9.30.2002 Corrected page number error in errata
9.29.2002 Added Q/A on automatic external ATUs
9.28.2002 Added Q/A about sticky switches
9.25.2002 Added Q/A on finding repair shops
9.23.2002 Added Q/A on TNC hookup
9.20.2002 Added Q/A on CT-17 cable
9.15.2002 Several minor changes and link updates
9.15.2002 More info on power drop off
9.09.2002 Added Q/A about low voltage operation/shutdown
9.08.2002 More info on IC-PW1 operation
9.06.2002 Added Q/A about Alaska Emergency Frequency
8.26.2002 More info on ignition noise
8.20.2002 More info on SEND connection problems.
7.17.2002 Added Q/A about 60m operation
7.15.2002 Added Q/A about IC-2KL amplifier birdies
==============================
CONTENTS
S:1. ADMINISTRIVIA
Q:1.1. What is an FAQ?
Q:1.2. Where can I get a copy?
Q:1.3. Where do I send feedback?
Q:1.4. What are the future plans for the FAQ?
Q:1.5. What questions still need to be answered?
Q:1.6. What does this abbreviation or TLA mean?
S:2. GENERAL INFO
Q:2.1. Should I buy an IC-746?
Q:2.2. What are the IC-746's features?
Q:2.3. How does the IC-746 stand up to the ______ ?
Q:2.4. Where can I buy/sell a used IC-746?
Q:2.5. How much is a used IC-746 worth?
Q:2.6. Is there a dedicated HF net for the IC-746?
Q:2.7. Are there electronic copies of 746 instruction manuals?
Q:2.8. Are there electronic copies of 746 service manuals?
Q:2.9. How do I fix the font substitution error in the PDF manual?
Q:2.10. How does an IC-746s differ from an IC-746?
Q:2.11. What is the IC-7400?
Q:2.12. What is the IC-746-PRO?
Q:2.13. Where can I find info on other Icom rigs?
Q:2.14. Where is info on the 706, 718, 756, 765, 735, ...
Q:2.15. What articles have been written about the IC-746?
Q:2.16. Can I transmit 100w at 100% duty cycle on CW/SSB/RTTY/PSK/etc?
Q:2.17. I thought the LCD was blue, but photos show it as green?
Q:2.18. Can the IC-746 work on the 60m band?
Q:2.19. Can the IC-746 work on the Alaska Emergency Frequency?
S:3. Accessories
S:3.1. Power Supplies
Q:3.1.1 What power supply should I use with the IC-746?
S:3.2. Antennas
Q:3.2.1 What antenna should I use with the IC-746?
Q:3.2.2 What range can the automatic antenna tuning unit (ATU) handle?
Q:3.2.3 Will the internal ATU handle "random" wire antennas?
Q:3.2.4 Will the internal ATU handle "long wire" antennas?
Q:3.2.5 Are there any "tips" to using the ATU?
Q:3.2.6 Can I use the internal ATU along with an external ATU?
Q:3.2.7 Does the internal ATU work on receive?
Q:3.2.8 Any other "gotchas" with the internal ATU?
Q:3.2.9 How do I use a "beverage" antenna?
Q:3.2.10 How do I use different antennas for receive vs. transmit?
# Split VFO Method
# External Antenna Switcher Method
# External RF Sense Antenna Preamp Method
Q:3.2.11 How do I measure SWR while in SSB?
Q:3.2.12 How do I tune up in CW without a key?
Q:3.2.13 What about using an external, automatic, ATU?
Q:3.2.14 Can I make the TUNER button activate an external automatic ATU?
Q:3.2.15 Why doesn't the rig SWR meter match my external SWR meter?
Q:3.2.16 Which SWR meter should I trust: internal or external?
Q:3.2.17 How do I repair the detector diodes in the internal ATU?
Q:3.2.18 How do switch between more than two antenna ports?
S:3.3. Microphones
Q:3.3.1 What is the best microphone to use with the IC-746?
Q:3.3.2 Can I use a dynamic/studio microphone with the IC-746?
Q:3.3.3 Can I use a Heil microphone with the IC-746?
Q:3.3.4 How do I adjust the IC-746 for a Heil headset?
Q:3.3.5 Do I need a pre-amp to use a Heil microphone?
Q:3.3.6 What are the pin-outs on the microphone connector?
S:3.4. Keyers
Q:3.4.1 Can I hook up my straight key to the front "Elec Key" Jack?
Q:3.4.2 Can I connect my own Electronic Keyer to the IC-746?
Q:3.4.3 How do I wire up my paddles for use with the internal keyer?
Q:3.4.4 Can I use the internal and external keyers at the same time?
S:3.5. Amplifiers
Q:3.5.1 How do I hook up an Icom IC-PW1 RF power amplifier?
Q:3.5.2 What if I hook up more than just an IC-PW1?
Q:3.5.3 How do I hook up a non-Icom RF power amplifier?
Q:3.5.4 Do I really need an external amplifier switching relay?
Q:3.5.5 Where can I get an external switching relay?
Q:3.5.6 Why do I need an external amplifier switching relay?
Q:3.5.7 My SEND relay seems to be stuck, what do I do?
Q:3.5.8 Can't I just use the ACC port to key my amp?
Q:3.5.9 How do I build my own SEND relay isolation circuit/relay?
Q:3.5.10 Why do I get IC-746 birdies when I turn on my IC-2KL?
S:3.6. TNC
Q:3.6.1 How do I hook up a TNC to the IC-746?
S:4. IF Filters
Q:4.1 How many optional IF filters can I install into the IC-746?
Q:4.2 What optional IF filters are available for the IC-746?
Q:4.3 Which optional IF filters should I buy?
Q:4.4 What is an IF filter's "bandwidth"?
Q:4.5 What is an IF filter's "shape factor"?
Q:4.6 Why do filter "bandwidth" or "shape factor" matter?
Q:4.7 What is considered to be a narrow filter?
Q:4.8 What are narrow IF filters used for?
Q:4.9 Can an IF filter be too narrow?
Q:4.10 What's the difference between IF filters from Inrad vs. Icom?
Q:4.11 Which IF should I put an optional filter into?
Q:4.12 What's different between IF filters for 9Mhz vs. 455Khz?
Q:4.13 What are the 9Mhz IF filters best for?
Q:4.14 What are the 455Khz IF filters best for?
Q:4.15 How do I get the best results from TPBT?
Q:4.16 How do I configure the IC-746 to use an optional filter?
Q:4.17 How do I configure the IC-746 to use a non-Icom filter?
Q:4.18 How do I use a CW filter in SSB mode to receive PSK31?
Q:4.19 Why is there only one optional 455Khz IF filter slot?
Q:4.20 Any tips on installing 9Mhz Inrad filters?
Q:4.21 Where do I install a 2nd Inrad 9Mhz IF filter?
Q:4.22 Where can I find more information on filter characteristics?
Q:4.23 What are some popular filter combinations?
S:5. Computer Control
Q:5.1 How do I wire the IC-746 up for computer control?
Q:5.2 What cables do I need?
Q:5.3 What are CT-17, OPC-478, OPC-662 all about?
Q:5.4 Do I need a special cable to connect a CT-17 to an IC-746?
Q:5.5 What is the control protocol for the IC-746?
Q:5.6 What is CI-V?
Q:5.7 What is the CI-V address of the IC-746?
Q:5.8 What computer software is available?
Q:5.9 Where can I get computer software and upgrades?
Q:5.10 Why doesn't computer software update freq when tuning the 746?
Q:5.11 How do I wire up the IC-746 for use with PSK31?
Q:5.12 Why isn't my computer control working?
S:6. Problems and Clarifications
Q:6.1 What's that funny rattling noise I hear when I first power on the rig?
Q:6.2 What's that "click" I hear as I tune across certain frequencies?
Q:6.3 Why doesn't the ALC meter work while adjusting the "mic gain"?
Q:6.4 Why can't I program any numbers into the memory names,
Q:6.5 How low can the IC-746 supply voltage be?
Q:6.6 Why isn't my output power up at 100 watts?
Q:6.7 The backlight in my LCD has stopped working. What's wrong?
Q:6.8 Is there some way to get the Icom-746 to generate DTMF tones?
Q:6.8 Why don't my "band edge beeps" match the US amateur bands?
Q:6.10 Can I transmit all the way out to the "band edge beeps"?
Q:6.11 Can I reprogram the "band edge beeps"?
Q:6.12 Do we know anything about the "band edge beeps"?
Q:6.13 How I reset back to factory default settings?
Q:6.14 What "birdies" does the IC-746 have?
Q:6.15 How do I adjust the LCD display?
Q:6.16 The Noise Blanker doesn't seem to do any good. What's wrong?
Q:6.17 How do I get rid of ignition noise?
Q:6.18 How do I adjust or make the NB work better?
Q:6.19 How do I fix a loose rubber grip from the tuning knob?
Q:6.20 Where should I go for repairs?
Q:6.21 How do I fix scratches on the LCD?
Q:6.22 Can I do about sticky switches?
Q:6.23 Why does the S-meter seems low on 2m FM?
Q:6.24 Why is my tuning shaft/knob loose and sloppy?
S:7. Modifications
Q:7.1 What TX/RX "mods" are there for the IC-746?
Q:7.2 What other "mods" are there for the IC-746?
# 6Khz wide IF filters
# Safe 2m TX/RX Sequencing
# Simple CAT interface
# Seperate 2m TX/RX Antenna Lines
# Increased MONITOR Volume
# LCD Driver Transistor Replacement
# Poor Man's TCXO
# Upgrading Stock Ceramic IF Filter to a Crystal Filter
Q:7.3 Can I increase my RF output beyond 100w?
Q:7.4 I'm brave; what untested "mods" are there?
# Replacing PIN Diodes in the Demodulator
# Removing the BCB Attenuator
Q:7.5 What "external" mods are there for the IC-746?
# Remote, Direct Frequency Entry Keypad
# Cordless Headset Microphone
# Automatic Antenna/Amplifier Selection by Band
# 2m TX/RX Sequencer
# External Tuner Pulser
S:8. Misc...
Q:8.1 Are there different versions of the IC-746?
Q:8.2 Can I operate 2m on reduced power?
Q:8.3 Where can I find plugs for the ACC connectors?
Q:8.4 What are the pin-outs on the ACC-1 connector?
Q:8.5 What are the pin-outs on the ACC-2 connector?
Q:8.6 Does audio to pin 4 of ACC-1 trigger the VOX?
Q:8.7 Where can I get replacement power connectors?
Q:8.8 Where can I get replacement microphone connectors?
Q:8.9 What is "Lo-Fi" SSB operation?
Q:8.10 What is "Hi-Fi" SSB operation?
Q:8.11 How does one improve the fidelity of a received signal?
Q:8.12 How does one improve transmission fidelity?
Q:8.13 Can the IC-746 transmit at less than 5 watts?
Q:8.14 How do I turn on both HF pre-amps at the same time?
Q:8.15 How do I adjust the 746 for best AM performance?
Q:8.16 Is the IC-746 suitable for CAP and MARS operation?
Q:8.17 How do I adjust the Noise Reduction (NR)?
Q:8.18 How do I program a non-standard repeater offset?
Q:8.19 How do I turn on repeater (PL) tones?
Manual Errata
Manual Discrepancies
Glossary
Contributors + Acknowledgements
Disclaimer + Copyright
==============================
S:1. ADMINISTRIVIA
------------------------------
Q:1.1. What is an FAQ?
Q:1.2. Where can I get a copy?
Q:1.3. Where do I send feedback?
Welcome to the IC-746 FAQ.
Short Answer
FAQ stands for "Frequently Asked Questions". It tries
to cover common questions/problems/issues associated
with Icom's IC-746 HF/VHF amateur radio transceiver.
The master copy is kept at:
http://groups.yahoo.com/group/IC746/files/IC746-faq.txt
Mirrored copies (after a short delay) appear at:
http://www.qsl.net/kb9sss/IC-746/IC746-faq.txt
An older version (June 2001) is sitting at:
http://www.skysdaughter.com/icom746-faq
You do not need a Yahoo email account to access the
master copy, however, you will need a logon account.
Yes, that is a subtle but hopefully minor distinction.
Not everyone is willing to have a login account at Yahoo
(even if it is free), which is one of several reasons
for maintaining the mirror sites.
Also, we post the FAQ monthly to:
news:rec.radio.amateur.equipment
usually sometime between the 1st and the 10th.
You can post questions/comments about the FAQ to
the above newsgroup.
Long Answer
The format of this FAQ should become apparent right from
the start. Questions are grouped into related sections
and subsections, roughly in the form of an outline.
Questions start in column one with their composite
section number.
When possible/practical, there will be both a short
and long answer. The short answers will try to be
brief and to the point, typically about one paragraph.
While correct, quick, and immediate, it will often gloss
over subtleties and details. The long answers will cover
theory, alternatives, dissenting opinions, and other
supplemental material. We try not to unnecessarily
duplicate information between the answers (this one
is an example of that). Long answers may go on for
several pages.
The questions that are addressed here (as well as the
answers) come from several sources.
This FAQ was originally created and hosted by folks on
a Yahoo e-mail discussion group at:
http://groups.yahoo.com/group/IC746
They have extensive information on the IC-746, including
bookmarks and a file download area.
www.qth.net hosts a more generalized Icom e-mail list
that covers all models, not just the IC-746. You can
lookup more information or subscribe to that list at:
http://mailman.qth.net/mailman/listinfo/icom/
There's a search engine, but it's accessed from a
Hallicrafters site at:
http://www.w9wze.org/
Some of the info here originally appear upon a bbs
style on-line discussion group that used to be at:
http://vartel.com/icom746/icom746index.html
(site not responding Jan-2002)
There are also the following newsgroups:
news:rec.radio.amateur.equipment
news:rec.radio.swap
Specific comments or clarifications can be sent directly
to the FAQ coordinator. "Content submissions" would be
greatly appreciated. However, general discussion/debate
over the answers is best done in a more public forum,
like one of those mentioned above.
------------------------------
Q:1.4. What are the future plans for the FAQ?
Many have suggested/asked that the FAQ take on a
graphical rather than text format to better facilitate
charts, photos, diagrams, etc... The two front running
formats are HTML and PDF, each of which has advantages
and disadvantages. I now have the tools to do both
and will be persuing it the second half of 2002.
Most of the power supply information will be separated
out into a separate FAQ that is applicable to all rigs.
This fits in better with the new ICOM Resource pages at:
http://www.qsl.net/icom/
------------------------------
Q:1.5. What questions still need to be answered?
There are plenty of topics that still need or deserve
to be covered. Here are some topics and details we'd
like information on (in no particular order):
* Levels and impedances of all audio connections
(mic, phones, acc, etc...)
* We still do not have enough reliable reports to
confirm which "birdies" (if any) actually exist.
* How does one go about hooking the 746 up for PSK,
TNC, and CI-V operations at the same time.
* CW Zero-Beat confusion
(as well as BFO and "reverse" operation)
* More information on the front panel power switch
and its interaction with the extra pins on the
T-connector in the back.
* More service and repair information
* Better explanation of band stacking registers
* Operating tips
* Instructions on how to use internal ATU
* Better explanation of COMP (gain, FM, etc...)
* Compare/contrast the 746 vs 746PRO
* Does the 746 exhibit a full power spike at beginning of TX?
We welcome and encourage submissions.
------------------------------
Q:1.6. What does this abbreviation or TLA mean?
Hams use a lot of abbreviations and TLAs (Three Letter
Acronyms), Toward the end of this document, is a small
glossary to some of the abbreviations we use in the FAQ.
==============================
S:2. GENERAL INFO
------------------------------
Q:2.1. Should I buy an IC-746?
Yes. Try it, you'll like it.
This FAQ is maintained by happy, loyal, and devoted
IC-746 owners. What do you really think we're going
to say?
One thing nearly everyone (both loyalists and detractors)
agrees upon is that you should make every effort to
try out a rig before purchasing it.
------------------------------
Q:2.2. What are the IC-746's features?
For features, check out the IC-746 specifications
from brochures available at your local amateur radio
equipment store, on-line documents at various vendor
sites, or directly from Icom's WWW site at:
http://www.icomamerica.com/
On-line copies of the IC-746 sales brochure are at:
http://www.qsl.net/kb9sss/IC-746/IC-746-Brochure.pdf
http://groups.yahoo.com/group/IC746/files/IC-746-Brochure.pdf
Of particular interest might be the on-line copy of
the instruction manual.
Most of the 746's problems or faults show up either in
this FAQ (eventually) or in one of the archives at:
http://groups.yahoo.com/group/IC746
http://mailman.qth.net/mailman/listinfo/icom/
------------------------------
Q:2.3. How does the IC-746 stand up to the ______ ?
Probably the most objective, quantitative comparisons you
will find are the QST product reviews (freely available
to ARRL members):
http://www.arrl.org/members-only/prodrev/
An Excel spreadsheet that allows side by side comparison of the technical specifications for many HF tranceivers can be found at:
http://groups.yahoo.com/group/IC746/files/HF-RIGS.xls
Simpler, more limited, comparison charts are available
on the Amateur Electronic Supply WWW site at:
http://www.aesham.com/compare/comp_hf.html
User written reviews can be both more personal and
more detailed. They can also be more biased. You can
find plenty of them at:
http://www.eham.net/reviews
This topic has come up several times on Yahoo's IC746
discussion group. One of the more interesting threads
along these lines starts with message 1012 and ends
with message 1028. I'm told that message 1023 is
particularly good. Another good thread starts with 1049
and ends with 1077.
http://groups.yahoo.com/group/IC746/message/1012
http://groups.yahoo.com/group/IC746/message/1023
------------------------------
Q:2.4. Where can I buy/sell a used IC-746?
Usually when someone asks this on the internet, they are
looking for an on-line swap page. There are, of course,
plenty of other options. Most dealers have used/demo
equipment. Hamfests are a traditional favorite, as are
"swap nets" on HF.
That said; the two largest forums on the internet for
amateur radio gear are the USENET newsgroup
news:rec.radio.swap
and the infamous eBay auction site.
http://www.ebay.com
"Amateur Radio Trader" is both a magazine and a WWW
site devoted to amateur radio classifieds:
http://www.amradiotrader.com
(site not responding Jan-2002)
Yahoo has a small auction site as well:
http://list.auctions.shopping.yahoo.com/23761-category.html?alocale=0us
After those, you have your choice of dozens of
dedicated swap sites on the net. A few of them are:
http://www.arrl.org/RadiosOnline/
http://www.qrz.com/forum/
http://www.eham.net/classifieds/
http://www.k1dwu.net/hamtrader/
AC6V maintains an entire list of swap pages as part
of his excellent ham links/resource site.
http://www.ac6v.com/swap.htm
------------------------------
Q:2.5. How much is a used IC-746 worth?
Unlike used cars, there is no official "blue book"
for ham equipment. Only YOU can decide this.
Your best bet is to peruse the archives for
news:rec.radio.swap
over the past 6 months or so.
You might also check out one of the following sites
Electronic Boneyard Prices:
http://www.geocities.com/CapeCanaveral/Hall/8701/ham/boneyard.htm
E-Bay prices:
http://aade.com/hampedia/prices.htm
Virtual Hamfest - Recent Prices:
http://www.vhamfest.com/prices.html
(site not responding Jan-2002)
Good luck.
------------------------------
Q:2.6. Is there a dedicated HF net for the IC-746?
Yes, one was started in October, 2001.
It convenes 20M SSB near 14.2525 Mhz +/- QRM, on
Sunday evenings at 9:00pm Eastern time (6:00pm Pacific).
The folks that run the net shift it along with Daylight
Savings Time in the U.S.A. Therefore, during "standard"
time (last Sunday in October to the first Sunday in
April) the net starts at 0200 UTC Monday. During
"savings" time (first Sunday of April through last
Sunday of October) the net starts at 0100 UTC Monday.
For the curious, not all of the U.S.A. participates in
"daylight savings time". Likewise, portions of Europe
participate, but on a different timetable. A wealth
of information on DST can be found via Yahoo at:
http://dir.yahoo.com/Science/Measurements_and_Units/Time/Daylight_Saving_Time
or within the AC6V link indices at:
http://www.ac6v.com/opaids.htm#CLOCKTIME
or directly from NIST (the National Institute of
Standards and Technology) at:
http://www.time.gov
The folks in the Yahoo IC746 e-mail group try to maintain
a net calendar at:
http://groups.yahoo.com/group/IC746/calendar
Yes, you have to be a member of the e-mail group to
access their pages, but as a fringe benefit, you'll even
get an automatic e-mail reminder on the day of the event.
Doug, N7BNT, located in Vancouver, WA is usually Net
Control, and "K.C." KG9JP in Phonenix, AZ is usually
helping out and hosting the chat room.
There is usually a IC746 chat room set up on Yahoo
Internet Messager. Click on the "Chat" button, go to
"Hobbies and Crafts", click on the "User Rooms" tab and
join in! If you need a relay to check-in to the net,
this is the place to go... The chat room should be up
about 10 minutes before net.
We've heard of a few other HF nets devoted to Icom
equipment in general. They meet at:
Sunday, 1700 UTC, 14.315 Mhz ssb
Sunday, 2100 UTC, 14.317 Mhz ssb
------------------------------
Q:2.7. Are there electronic copies of 746 instruction manuals?
YES! During the first week of November, 2001, Icom
made an electronic copy of the IC-746 Instruction Manual
(along with many others) available on their WWW site at:
http://icomamerica.com/support/documents/index.html
A backup copy of the manual is stored in the IC746
Yahoo group's "Files" area at:
http://groups.yahoo.com/group/IC746/files/IC-746-Instruction-Manual.pdf
as well as at the QSL.NET ICOM Resource pages:
http://www.qsl.net/kb9sss/IC-746/IC-746-Instruction-Manual.pdf
Additionally, the FCC posted the IC-746pro instruction
manual (and various other documents) at:
http://gullfoss2.fcc.gov/cgi-bin/ws.exe/prod/oet/forms/reports/Search_Form.hts?mode=Edit&form=Exhibits&application_id=740578&fcc_id=AFJIC-746PRO
A backup copy of both parts of this manual is stored
in the IC746 Yahoo group's "Files" area at:
http://groups.yahoo.com/group/IC746/files/IC-746pro-Instruction-Manual-1.pdf
http://groups.yahoo.com/group/IC746/files/IC-746pro-Instruction-Manual-2.pdf
Another good place to look for on-line manuals is:
http://www.mods.dk/
While Icom has relaxed a little in providing these
documents, they are still protected by copyright.
Please, treat them accordingly. Remember, Icom is
doing us a favor.
------------------------------
Q:2.8. Are there electronic copies of 746 service manuals?
No such copies are known to exist, although they would
quickly become popular if they did. As of May 2001,
Icom had no plans for releasing one. Additionally,
Icom considers any such external productions to be a
violation of their copyright. Ray (the product manager
at the 2001 Hamvention) was very firm on this.
Hard copies are available through any Icom retailer as
well as through the W7FG Vintage Manual WWW site at:
http://www.w7fg.com/
------------------------------
Q:2.9. How do I fix the font substitution error in the PDF manual?
When trying to read the PDF version of a 746 Instruction
Manual with the Adobe Acrobat Reader, some people
encounter the following three dialogs on page 10 of
the document (PDF page 12).
A font required for font substitution is missing.
An error has occurred that may be fixed by
installing the latest version of the Japanese
Language Support package.
Unable to find or create font
"Ryumin-Light-Identity-H". Some characters may
not display or print correctly.
The error is not fatal. There are a few dozen places
in the manual where text in diagrams will show up as
a series of dots.
You can get rid of the error by downloading the
appropriate Asian font package directly from Adobe's
support pages. As of November, 2001, the appropriate
link was:
http://www.adobe.com/support/techdocs/2a156.htm
------------------------------
Q:2.10. How does an IC-746s differ from an IC-746?
Japan has a 3rd Class license that is power limited
(sort of like the defunct US Novice class). The IC-746s
is identical to the IC-746, except that it caters to
this limited operating class. It's output power is
limited to 10w on HF and 20w on VHF.
Nobody has yet reported a "mod" for this rig to bring
its power up.
------------------------------
Q:2.11. What is the IC-7400?
Q:2.12. What is the IC-746-PRO?
These are both successors to the IC-746. The IC-7400
is the Japanese version while the IC-746-PRO is the
English version. We don't know yet what else (if
anything) differentiates them besides their name.
There are two ways to look at the IC-746-PRO. Some
view it as a beefed up IC-746 while others view it as
a watered down IC-756-PRO. On the outside, it looks
and operates very much like the IC-746. The controls
are similar enough that you confuse the two. However,
the inside (RF chain and DSP) is more like the IC-756-PRO
than anything else.
Here are some features that the IC-746-PRO has over
the IC-746:
+ 32bit DSP with 24bit ADC
+ Selectable digital filters (50+)
+ Sharp or Soft filtering (via DSP)
+ Digital TPBT
+ Manual digital notch filter (in addition to ANF)
+ Twinned Digital APF (great for RTTY?)
+ DSP based RTTY decoder
+ Adjustable digital noise blanker
+ Digital TX/RX equalization (instead of analog)
+ Digital speech compressor (instead of analog)
+ Digital voice recorder
You'll notice how prominently the DSP plays in this rig.
One thing the original 746 has over the 746-PRO is an
additional IF stage, thus its TPBT is actually going
through two offset IF filters. The 746-PRO achieves its
TPBT via the DSP. Its argued that the DSP filtering more
than makes up for the lack of the extra filter and is
more programmable/flexible. It's counter argued that DSP
filtering is not as effective as traditional IF filtering
(the 746-PRO instruction manual even eludes to this) and
that insufficient filtering early on overtaxes the DSP.
Both are excellent rigs and only time will tell just
how effective DSP really is. Perhaps someday Icom will
make a rig with both.
Here are some of the features the IC-756-PRO has
that the IC-746 does not.
- Dual watch receiver design
- Real-time spectrum scope
Additionally, the IC-746-PRO retains the basic form
factor, LCD, control layout, and bonus 2m capabilities
of the IC-746.
Plenty of sales and technical information is available
(including downloadable pictures and brochures) from
Icom's WWW site at:
http://www.icomamerica.com/
There is a Yahoo discussion group devoted to the IC-7400,
as well as a group devoted to the 746 series in general.
http://groups.yahoo.com/group/IC7400
http://groups.yahoo.com/group/IC746
Icom has not yet made a copy of the IC-746-PRO
instruction manual available in electronic form, however,
the FCC has. You can access it and other information at:
http://gullfoss2.fcc.gov/cgi-bin/ws.exe/prod/oet/forms/reports/Search_Form.hts?mode=Edit&form=Exhibits&application_id=740578&fcc_id=AFJIC-746PRO
And a nice ham-written synopsis appears at:
http://www.qsl.net/ab4oj/ja7ude/ic7400.html
http://www.qsl.net/ab4oj/icom/ic7400/ic7400.html
------------------------------
Q:2.13. Where can I find info on other Icom rigs?
Q:2.14. Where is info on the 706, 718, 756, 765, 735, ...
This FAQ is devoted to the IC-746. As of November, 2001,
we do not know of any FAQ's devoted to other Icom models.
However, as of Jan-2002, a project was underway to start
accumulating and centralizing Icom information at:
http://www.qsl.net/icom/
While the coordinators of this list already have their
hands full, they would be glad to advise, help, and
collaborate with people interested in maintaining
other FAQs.
Much of the generic information in this FAQ is applicable
to other Icom rigs, but please, use common sense when
trying to apply it.
For general information on other Icom rigs try:
Icom's WWW site at:
http://www.icomamerica.com/
Icom e-mail discussion group at:
http://www.qth.net
Usenet newsgroup:
news:rec.radio.amateur.equipment
The definitive collection of "mods" for all makes and
models of amateur radio equipment is at:
http://www.mods.dk/
Yahoo Groups hosts more than 40 e-mail/WWW discussion
groups related or devoted to Icom equipment. Here are
some of the more than 50 Icom related groups there.
http://groups.yahoo.com/group/icomr2
http://groups.yahoo.com/group/ICOMR3
http://groups.yahoo.com/group/ic706
http://groups.yahoo.com/group/ICOM706
http://groups.yahoo.com/group/IC-706Mk2G
http://groups.yahoo.com/group/IC-756PRO
http://groups.yahoo.com/group/ic756pro2
http://groups.yahoo.com/group/IC-Q7
http://groups.yahoo.com/group/IcomRadio
IC-765 information pages
http://www.execulink.com/~dstalk/
Last, but certainly not least, AC6V has a wealth of
links and resources on amateur radios.
http://www.ac6v.com/swap.htm
------------------------------
Q:2.15. What articles have been written about the IC-746?
A Microphone Adapter for the IC-706
Davidson, Taylor, N4TD
May, 2002, QST, p.38
A microphone preamp/control project that could
be easily adapted to the IC-746.
A Quality Sound Card Interface for ICOM Rigs
Lewis, Bob, AA4PB
March, 2002, QST, p.31
A great way to capitalize upon ACC port 1.
Solving Sound Card Microphone Problems
Covington, Michael A., N4TMI
June, 2000, QST, p.61
Shows a tiny, phantom powered, mic preamp
Automatic Amplifier Selection for the ICOM IC-746,
IC-736 and IC-706MKII Transceivers
Hewitt, Paul, WD7S
May, 2000, QST, p.33
Operating via the ACC connector (thus bypassing
the SEND relay), this project provides automatic
amplifier keying (with ALC selection) based on
the Icom band signal.
A Direct Frequency Entry Keypad for ICOM Transceivers
Hansen, John, W2FS
December, 1999, QST, p.38
Adds an external keypad via a PIC and CI-V.
ICOM IC-746 MF/HF/VHF Transceiver (Product Review)
Wolfgang, Larry, WR1B
September, 1998, QST, p.70
A product review article
Der Neue von Icom: IC-746 - mit 100w und DSP auf 11 Bandern
Petermann, Bernd, DJ1TO
April, 1998, Funkamateur, p.392
A product review article (German)
A Remotely Controlled Antenna Switch
Thompson, Nigel, KG7SG
April, 1993, QST, p.32
Uses the band signal on the Icom ACC connector
to remotely switch between antennas with a
single feedline. (This article predates the 746,
but is still appliccable)
------------------------------
Q:2.16. Can I transmit 100w at 100% duty cycle on CW/SSB/RTTY/PSK/etc?
Yes. All of the 746/756 series were designed to
handle continuous 100w output in all modes.
The rig will get quite warm and the fan will
run continuously. Be sure you allow adequate
ventilation.
------------------------------
Q:2.17. I thought the LCD was blue, but photos show it as green?
The screen is blue. The green color that shows up in
many photos is caused by the camera flash, sort of
an optical illusion. Non-flash photos always show the
screen as blue.
For an example, see N4WMX's 746 non-pro at:
http://www.backroadadventure.net/gallery/Radio/aaj
------------------------------
Q:2.18. Can the IC-746 work on the 60m band?
Q:2.19. Can the IC-746 work on the Alaska Emergency Frequency?
Yes, no, no, and yes. To both questions.
For the purposes of our discussion, the Alaska Emergency
Frequency of 5.1675 MHz USB is can be treated as part
of the 60m band.
Yes, the IC-746 can receive the 60m band, and does
so quite nicely. No, as shipped, the IC-746 will not
transmit on the 60m band. No, there is no 60m specific
mod to the rig but yes, there is an all-band mod that
will allow the IC-746 to transmit on the 60m band. See:
http://www.mods.dk
Of course, once you've opened up ALL of the bands this
way, appropriate caution is dictated.
The IC-756 (original, not the pro) has a very similar
design to the IC-746. Some IC-756 users report an
output power dropoff near 5 MHz, presumably due to the
output band pass filters. Annonymous reports indicate
that the 746 does not suffer the same problem. I do
not have any data on the 746-PRO.
==============================
S:3. Accessories
------------------------------
S:3.1. Power Supplies
------------------------------
Q:3.1.1 What power supply should I use with the IC-746?
Short Answer
Any good quality, communications grade, power supply
rated at least 20 amps or more (continuous duty) should
do just fine. However, most of us use larger supplies
(for a variety of reasons).
Popular supplies that are known to work (via testimonial):
Alinco DM-330MVT 30/32A switching
Astron RS-35M 25/35A linear
Astron SS-30 25/30A switching
Astron SS-25 20/25A switching
MFJ 4125 22/25A switching (MightyLite)
MFJ 4225 22/25A switching
MFJ 4035-MV 30/35A linear
Samlex SEC-1223 23/25A switching
Kenwood PS-52 20/22A linear
Power supplies to avoid (via testimonial):
Astron RS-20 - overloads too easily
Kenwood PS-30 - overloads too easily
Diamnond GZV-4000 - RF hash on 40/20m
Icom PS-85 - RF hash
Long Answer
This question typically arises for one of two reasons.
Either someone wants to buy a new power supply, or they
have an existing power supply that they want to use.
In both cases, the issues are: load capacity, size,
weight, electrical noise, mechanical noise, cost,
features, and appearance. Buying a new supply gives
you a lot of options; there are plenty of great supplies
out there. With an existing supply, you have no control
over these factors; you're simply looking for a "fit".
You'll want to consider the following factors.
## Reviews
QST tested and reviewed many supplies in January and
September, 2000. You'll find the results informative.
ARRL members can access those and other reviews
on-line at:
http://www.arrl.org/members-only/prodrev/pdf/pr0001.pdf
http://www.arrl.org/members-only/prodrev/pdf/pr0009.pdf
## Transportability
The larger the capacity, the larger and heavier
the supply. If size and weight are critical for you,
consider a "switching" supply as they are usually less
than half the size of a "linear" supply.
## Electrical Noise
All supplies generate some electrical noise. Typically
the noise from linear supplies will be in the form of
AC hum while from switching supplies the noise will be
RF hash. Communications grade power supplies of either
type are designed to minimize the noise, and generally
cause no problem. (i.e. this is not a good place to
cut corners)
"Computer" power supplies that are pressed into radio
service are particularly bad when it comes to electrical
noise.
Usually, the harder you push a supply (the heavier the
load), the worse the noise will become.
## Mechanical Noise
Many supplies have cooling fans. Sometimes, the fans
are loud enough to be a noise problem themselves.
Fan noise is variable from supply to supply (even
within the same manufacturer and model). Likewise,
hearing tolerance varies from operator to operator.
Thus, it's hard to tell in advance if a specific supply
will have a problem. Time may yet tell.
We do know that fans are driven by load. The closer you
operate to a supply's capacity, the more the fan runs.
Also, some of the transformers used in linear supplies
will generate an audible hum. The transformer itself
vibrates with the AC supply. Mass seems to help here.
Usually (not always) the heavier the transformer,
the less the hum.
Its pretty easy to put a noisy power supply under a
table, behind a cabinet, or elsewhere to cut down on
the noise level. Just be careful to allow proper air
flow for cooling.
## Features
Most of us consider current limiting, over voltage
protection, and high temperature shutdown to be mandatory
in a new supply.
Fuses or breakers are required for UL certification.
Buy spare fuses right away; they never blow at a
convenient time.
Meters are non-essential, they are luxury items. They
make the supply bigger and more expensive. However,
they can be very handy and even fun. Lets face it,
most hams enjoy gadgets.
Adjustable output voltage is a useful feature, more
useful than you might realize. Most new supplies have it
(usually internally).
## Load Capacity
The size, weight, and cost of a power supply all tend to
increase with its load capacity. Those factors encourage
us to get the smallest supply we can. There are also
factors that encourage larger supplies; such as noise,
heat, accessories, etc...
The IC-746 specifications list a current drain at
maximum transmit power of 20A at 13.8Vdc. Thus, the
recommendation that your supply should handle 20 amps
(or more) continuously.
It is possible to run the IC-746 with a smaller supply,
but extreme caution and discipline are required. Very
few, if any, of us recommend it for normal operation.
For example, the 20 amp maximum in the IC-746
specifications is full key-down at full power.
You could just lower your RF power to help match your
load to the supply. You could even run the IC-746 QRP,
drawing as little as 3-4 amps on transmit.
Another factor is operating mode. Some of us have
measured full-key loads as high as 21-22 amps.
Normal SSB transmit at full power draws 6-15 amps.
But FM, digital, and CW will generally pull 18-20 amps
at full power.
## Continuous vs. Intermittent Load
There are issues concerning a supply's "intermittent",
"peak", or "surge" capacity. A supply might be rated
for 16 amps continuous and 20 amps peak. Normally, the
IC-746 runs at about 2-3 amps for receive and only hits
the 20 amp maximum during transmission. Thinking of
transmitting as "peak" or "intermittent" activity can
lead one to think that such a supply is acceptable.
It might even be. However, a problem develops when we
try to define what peak or intermittent activity is.
Everyone would agree that transmitting for 3 minutes
at 20 amps till the repeater time-out cuts you off is
not a peak. How short a time constitutes a peak and
at what duty cycle? Without some sort of specification
or standard, "peak" and "intermittent" could mean just
about anything. Most of us feel more comfortable with a
"better safe than sorry" approach.
This dual rating system for power supplies is a great
source of confusion. Specifically, you could buy a power
supply rated for 20A and have it fail under full load.
The Astron RS-20 and Pyramid PS-21 are examples of
such supplies. While both are excellent supplies,
they just can't keep up with an IC-746 under full power.
The exact definition of intermittent, peak, or surge
as used by the power supply manufacturers has not
been established.
(Some of us are going to try to talk to the
supply manufacturers about this to get more
details)
To quote a tech from Samlex:
Maximum rating is surge current requirement for
starting reactive loads or short term dynamic
loading and is limited to a few seconds.
This supply is not designed for pulsing loads.
Currents beyond the maximum rating will force the
unit into current limit and the output voltage
will drop and it will no longer be regulated.
Meanwhile, MFJ said (of the MFJ-4322):
Our units will shut down at surge. At 25 amps
surge, the power supply will shut down at about
ten seconds.
So while it is theoretically possible, most people do
not use supplies rated less than 20 amps continuous.
In fact, most use substantially bigger supplies.
## Bigger Supplies
Why use a bigger supply? There are several reasons.
As noted earlier, the closer you operate a supply to
its rated capacity, the greater the electrical noise,
mechanical noise, heat, etc...
Strain leads to wear-and-tear. So it can be argued
that a bigger supply should last longer.
The IC-746 is rated at 20 amps max, but loads as high as
21-22 amps have been measured. "Your mileage may vary"
definitely applies.
The continuous rating is generally based upon an
ambient air temperature of 20 C. The rating degrades
as the temperature rises, by how much, we're not sure.
Filed Day conditions will be stressful to your supply.
13.8 V times 20 A yields 276 watts. There's a tendency
for some supplies to drop voltage a little when they
get hot or overloaded. There's also a tendency for
some radios to increase their current pull when the
voltage drops. At 12 Vdc, that same 276 watts would
imply 23 amps. You push the supply capacity, which
drops voltage a little, which drives the rig current
up, which pushes the supply further ... then BANG.
You blow a fuse. (AK6R has actually seen this effect
with his 756pro)
There are plenty of other devices that need DC power.
You need to account for them as well.
Other and future rigs may have greater power demands
(like the 756pro). Extra capacity now may avoid the
need to upgrade your supply in the future.
You might well spend most of your time in a low power
situation (SSB QRP) and get by with less than 5A.
But, in an emergency, you and your gear may be called
upon to operate in different modes, at higher power,
and with heavier duty cycles. Planning ahead for the
worst case usage helps prevent an untimely failure at
just the wrong time.
## Conclusion
So, you'll find most of us with power supplies ranging
from 20 to 30 amps continuous; and some with even
bigger supplies.
------------------------------
S:3.2. Antennas
------------------------------
Q:3.2.1 What antenna should I use with the IC-746?
Short Answer
Any antenna you want.
Long Answer
Seriously. ANY antenna will work with the IC-746,
with the proper interfacing. People have even made
contacts using dummy loads.
Antennas are probably the most uniquely individualistic
aspect of any ham station. Antenna selection is a BIG
topic; much too big to deal with in an FAQ (at least
for this one).
The IC-746 has 50 ohm, unbalanced, coaxial RF outputs.
With the automatic ATU capable of handling SWR mismatches
of up to 3:1 on HF (and 2.5:1 on 6 meters), you have
a wide variety of choices available to you.
There are many excellent books on the topic; the ARRL
has a couple dozen of them. A good one to start with is:
The ARRL Antenna Book
At over 800 pages (and over 1,000 antennas), you're
sure to find SOMETHING that fits your style and budget.
For more information, try hanging out on one of over
50 e-mail groups on the topic at
http://groups.yahoo.com
or visit one of the hundreds of antenna oriented WWW
sites indexed by AC6V:
http://www.ac6v.com/
http://www.ac6v.com/antprojects.htm
or follow along with the discussions on the newsgroup:
news:rec.radio.amateur.antenna
or visit the on-line antenna magazine:
http://www.antennex.com/
or, you could just put up a trusty old dipole.
Just be sure you do use an antenna. The IC-746 does not
like to transmit into an open load (no connected antenna).
It will put an undue (and possibly fatal) strain on your
output transistors.
------------------------------
Q:3.2.2 What range can the automatic antenna tuning unit (ATU) handle?
Officially, the automatic ATU in the IC-746 can handle SWR
mismatches of up to 3:1 on HF and up to 2.5:1 on 6 meters.
In practice, many people get even wider ranges, a few as
high as 7:1, but be wary of pushing the ATU that hard.
The ATU does not function on 2 meters.
Some have pointed out that, even though the internal tuner
may tune a particular antenna configuration, if there
is a high SWR, you could end up burning out the tuner.
We have at least one case (reported by KG6GLN) where the
detector diodes in an IC-746 were fried. According to
the ICOM tech, "... it could happen if you tried to
use an external antenna tuner in conjunction with the
internal tuner. "
------------------------------
Q:3.2.3 Will the internal ATU handle "random" wire antennas?
Q:3.2.4 Will the internal ATU handle "long wire" antennas?
No. You'll need an external ATU.
The internal ATU can only handle an SWR mismatch of
about 3:1 on HF and 2.5:1 on 6 meters. Such antennas
will exceed those limits somewhere, over stressing
the ATU and possibly blowing it out. Matching will be
hit or miss (mostly miss).
Of course, there's always an exception. N4EUK reports
successfully tuning his 100 foot wire antenna using
the internal ATU. Even he was surprised.
------------------------------
Q:3.2.5 Are there any "tips" to using the ATU?
You mean, besides the tips already provided on page 58
of the Instruction Manual? Yes.
The ATU appears to pay attention to the reflected
power, not the SWR. [Note: we'd love someone to
analyze the schematics to confirm or deny this.]
This is evidenced by two effects.
When starting from a close match at QRP power levels,
the auto ATU doesn't always home in on the best match.
Increasing the power level and tuning again often
improves the match, which the ATU then retains when
returning to QRP power. In fact, the manual mentions
at least 8w on HF and 15w on 6m.
The converse situation can also cause trouble.
When starting from a poor match at full power, the auto
ATU sometimes can't find a match at all. In this case,
tuning at lower power allows the ATU to get a match,
which the ATU then retains when returning to high power.
If one end of a band consistently gives you trouble
while the other end tunes easily, then you may still
be able to coax the ATU into matching the antenna.
Start in the portion of the band where the ATU works
and tune there. Then, move your way across the band
in increments (maybe 25Khz at a time), tuning as you
go until you reach the desired portion.
------------------------------
Q:3.2.6 Can I use the internal ATU along with an external ATU?
Maybe. Theory says yes, but Icom says no. The results
are mixed. Use at your own risk.
Many people use an external ATU along with their IC-746.
Usually, they leave the external ATU switched to "bypass"
and let the internal ATU do its thing. For troublesome
bands/antennas, they turn off the internal ATU and
engage the external one.
Others use an external ATU to match their antenna to
the middle of the desired band and let the internal ATU
handle the rest. In theory, the ATU doesn't know or
care what's hooked up to it; it simply tries to match
up to the impedance it sees.
In most cases, either of the above approaches work fine.
Many hams have been applying both for years with no
problems.
However, some IC-746's have had their ATUs go out from
fried detector diodes and driver transistors. On many
repairs, Icom has blamed the failure upon external
tuners. One ham was told that external tuners can
cause problems even when they are switched to "bypass".
Nobody has been able to adequately explain why an
external tuner would cause such damage, particularly
when bypassed. Some speculate that tuning with low
power is safer than tuning with high power (if nothing
else, its at least more polite).
We need more information on this, but at least you've
been warned.
The best procedure we can suggest at this point is:
* Turn off the internal ATU.
* Reduce power to about 1/4 (25w).
* Adjust the external ATU using the rig's SWR meter.
(The two meters usually disagree. It is what the
rig sees that is important.)
* Restore full power.
* Turn on the internal ATU.
Do not adjust the external ATU at full power.
Do not adjust the external ATU while the ATU is on.
Do not change frequency while the ATU is searching for
a match.
------------------------------
Q:3.2.7 Does the internal ATU work on receive?
Yes. The internal ATU is enabled while receiving.
Of course, it can only "match" while transmitting.
It's unclear if the internal ATU acts as an additional
preselector when enabled.
------------------------------
Q:3.2.8 Any other "gotchas" with the internal ATU?
We've already mentioned above the possible hazard
of using the internal ATU and an external ATU at the
same time.
We've also mentioned above that operating the internal
ATU at the limits of its abilities might overtax it
over time.
A possible problem we haven't already mentioned may
stem from the possible similarity between the IC-746
and the IC-756. The IC-756 users have been warned not
to use either their "Auto Tune" or "PTT Tune" features
while on 6m. (even the manuals mention this, although
in passing). Several have damaged their internal ATUs
this way, causing them to get stuck in 6m operation
after damaging the relays.
It has been speculated that some of the reported mishaps
with the IC-746 internal ATU with 6m may be related.
It's not hard to imagine that the 746/756 share a common
ATU design. We'd appreciate someone (with access to
both service manuals) doing a detailed circuit comparison
to confirm/refute this.
Finally, the internal ATU is only matching at the
internal PA. You'll still have high SWR out on your
coax, as expected.
------------------------------
Q:3.2.9 How do I use a "beverage" antenna?
Q:3.2.10 How do I use different antennas for receive vs. transmit?
As previously stated, nearly ANY antenna can be used
with the IC-746, provided it can be matched to the
746's 50 ohm, unbalanced antenna terminals. However,
there is more to using a "beverage" antenna than just
impedance matching.
Beverage antennas tend to sacrifice gain in order to
improve their signal to noise ratio. So, while they
are good for receiving, they are poor for transmitting.
Therefore, you would typically use a separate antenna
for transmitting.
# Split VFO Method
While not convenient, the IC-746 can be configured to
use one of its antenna ports for transmitting and the
other for receiving. Run the rig in split mode with
both VFOs on the same frequency, but have VFO A use
antenna 1 and VFO B use antenna 2.
# External Antenna Switcher Method
A more traditional approach (albeit, more work) is to
take the HF transmit signal from one of the accessory
ports activate a coaxial relay (via a driver transistor)
to switch between antennas. This is the same basic setup
you would use to control an external amplifier.
(refer to articles and external amplifier questions
for more information)
# External RF Sense Antenna Preamp Method
Some manufacturers make antenna preamps that sense the RF
on the line to switch between antennas as well as switch
in/out the preamp. The Ameco PT3 preamp is one example.
------------------------------
Q:3.2.11 How do I measure SWR while in SSB?
Usually, you don't. Measuring SWR requires a signal.
The only way to get a signal on SSB is to modulate;
i.e. you talk.
The simple thing to do is to switch modes to either
AM or RTTY briefly. After making your measurement,
switch back to SSB.
------------------------------
Q:3.2.12 How do I tune up in CW without a key?
Usually you don't. You probably don't even want to
be in CW mode without a key.
Odds are, you're trying to tune up for a different
mode, for example, PSK on SSB. The simplest thing
to do is switch briefly to AM or RTTY and tune there.
If you insist upon tuning up in CW without a key,
then you really only have one option; simulate a key.
You could turn on the mic-keyer, which uses the scan
buttons (UP/DN) operate the keyer. Or you could wire
up a dummy key jack and key the rig by plugging the
dummy jack in and out. There's even one ham who uses
his headphones as a dummy key, but very few of us are
willing to take that risk!
------------------------------
Q:3.2.13 What about using an external, automatic, ATU?
There are many automatic ATUs you could use. Your choice
boils down to two basic questions:
Do you want to tune at the antenna or in the shack?
Do you want an Icom tuner or a third party tuner?
Tuning at the antenna is far more efficient than
tuning in the shack (feedline SWR, etc...), however
tuning in the shack is more convenient (no power or
control cables).
Icom tuners will be "plug-n-play" with the IC-746,
while third party tuners may require cabeling or a
change in procedure.
Remember, the transceiver's internal ATU must always be
disengaged when driving an external tuner. Cascading
tuners can reflect high reactance values back into
the internal ATU and/or LPF. As a result, dangerously
high RF voltages can appear across capacitors in these
networks, leading to component failure.
Icom's cabling
to their own antenna tuners takes care of the above automatically.
There are too many possible automatic ATUs to cover in
this document, but here are a few that merit special
comment.
## AT-180
The AT-180 is intended for use in the shack with
near-resonant antennas; it will tune a maximum excursion
of 3:1. The AT-180 was designed for the ham bands only
but should have sufficient band overlap to accommodate
the MARS frequencies.
Here are the AT-180 specifications:
http://www.icomamerica.com/amateur/hf/at-180.html
No real point to using this ATU over the built-in one
## AH-4
The AH-4 is an automatic antenna coupler, intended to
tune random-length wire and whip antennas. The AH-4 is
mounted at the antenna, and the RF lead from the coupler
to the radiator should be as short as possible. The
AH-4 covers 3.5 to 54 MHz (continuous) with a 7m (23 ft)
wire antenna.
Here is the AH-4 brochure:
http://www.icomamerica.com/support/documents/brochures/ah-4.pdf
And a very informative site on the AH-4 (including an
AH-4 FAQ):
http://www.hamoperator.com/ah4/ah4.htm
## AH-3
The AH-3 is an older (out of production) alternative to
the AH-4; it covers 1.8 to 30 MHz (continuous) with a
7m wire antenna. There is info on it at the following
WWW site:
http://www.qsl.net/n4pl/ah3/
## AH-2
Older still, the AH-2 could cover 1.8 to 30 MHz with a
12m antenna or 3.8 to 30 MHz with a 3m antenna.
------------------------------
Q:3.2.14 Can I make the TUNER button activate an external automatic ATU?
Yes. The IC-746 has a connector designed to directly
connect to the Icom AH-4 automatic antenna tuning unit.
Page 80 in the instruction manual describes hookup and
operation. Once installed, pressing the TUNER button
for 2 seconds will cause the rig to transmit 10w in CW
mode until the AH-4 finishes.
The IC-746 assumes that the AH-4 is connected to ANT-1
and automatic tuning will only work there. ANT-2 is
still available, but with no ATU.
In fact, there's a whole WWW site devoted to the AH-4.
Check it out at:
http://www.hamoperator.com/ah4/ah4.htm
Most Icom tuners use the same interface (AH-2, AH-3,
AT-180, etc...).
Connecting and operating an LDG tuner is exactly the
same; they even make a cable specifically for the task.
Connecting and operating an SGC tuner is almost the
same; you'll have to make your own interface cable.
Instructions for that are at:
http://www.sgcworld.com/products/Couplers/icom706.html
Sure, the page says its for the IC-706, but the external
ATU interface is identical to that of the IC-746. Once
wired up, operation will be just like for the AH-4.
Finally, you could just fake the IC-746 into thinking
that there is an ATU out there with a dummy plug like
that available from W2ENY at:
http://members.fortunecity.com/w2eny/tenatuner/
Operation is similar to that for the other tuners, but
transmission stops after an 8 second timeout instead of
by tuner acknowledgement. You can even build this
yourself based on the information at:
http://www.mods.dk/mods.php3?radio=icom&model=ic-706&selectid=1864
or
http://www.qsl.net/wb8rcr/706Tune.html
http://www.qsl.net/g4fzn/706cct.gif
Don't mind that the info says its for the IC-706, all
Icom rigs from this era use the same circuitry/connector.
------------------------------
Q:3.2.15 Why doesn't the rig SWR meter match my external SWR meter?
Its normal for different points along the RF "feed"
to register different SWR readings. The SWR meter in
the 746 reads the SWR between the final amplifier stage
and the tuner. Your external SWR meter reads the SWR
between the tuner and the antenna. The external meter
should always read greater than or equal to the meter
in the 746.
Its actually possible to "match" your rig to your
antenna by simply changing the length of your feedline.
For an extreme (but very workable) example, check out:
http://www.qsl.net/w5dxp/notuner.htm
This is not to say that the internal SWR meter is
accurate. Posts that suggest that the internal SWR meter
reads lower at lower output power than at full output
power. The effect is noticeable, but not pronounced.
------------------------------
Q:3.2.16 Which SWR meter should I trust: internal or external?
Both can be trusted, but tune by the internal meter.
You probably care because you are using an external
ATU. Tune to bring the internal meter to a minimum
reading. Its the meter that tells you how happy your
RF power transistors are and whether or not you're
suffering SWR power foldback.
------------------------------
Q:3.2.17 How do I repair the detector diodes in the internal ATU?
???? (Mike) describes his experinece at fixing blown
detector diodes in the internal ATU.
-----
The problem was that the Auto-Tuner would no longer
tune up the antennas that it used to for me, and the
SWR didn't change on the antennas (as measured by my
MFJ-259 antenna analyzer). It would either try for
6-10 seconds and then drop out, or try for only one
or two seconds and drop out. When it "dropped out",
the Tuner indication would go away on the display.
Rather than sending it in for repair, I managed to
figure out the bad parts were the D8 and D9 Diodes on
the Control Unit. They are HSM88AS diodes. They are a
3 lead device, and look like a surface mount transistor.
They have "C1" indication on the top. These diodes
are located NEXT to the orange "L9" inductor close
to the speaker, just below the 820pf caps near the
open core inductors.. If you have trouble locating
it from the discription above, you'll either need the
manual from Icom to locate the two diodes, or I have a
picture that I took is available showing the location.
Looking at the specs for these diodes
http://www.hitachisemiconductor.com/sic/jsp/japan/eng/products/standardics/diod/lineup/diode/eHSM88AS.pdf
they have a minimum 10 V (sub)R voltage rating (not
too high) which may explain why they blow so easily
(but then I don't know the signals that they receive
under normal circumstances).
Notice also from the specifications that each part really
has 2 internal diodes. By looking at the schematic for
the radio (that comes with your Owners Manual, D8 and
D9 both have open leads where one diode is NOT used.
They are on OPPOSITE sides!! What you can do (one
time only) is to swap D8 and D9 and the radio should
work again. I found that the D8 diode was leaky.
I never did find the D9 diode to be able to measure it
(notice the warning below!)
HOWEVER, this repair procedure is not for the faint
hearted.
These are surface mount parts and are about the size
of 2 grains of sand. To replace the parts requires a
very small tip soldering iron, a fine tipped pair of
tweezers and a very steady hand.
What I did was to use some solder wick to remove much
of the solder. I was then able to remove the parts with
reasonable ease. Just as a warning, when I changed mine
out, once the solder joint released, my D9 when flying.
I never did find it. Lucky I had already ordered spares.
If you're brave enough to try it, I'll wish you the
best of luck, and add that I give no guarrentees that
this will fix your rig, but it did fix mine.
------------------------------
Q:3.2.18 How do switch between more than two antenna ports?
With a switch, of course.
Actually, you're probably looking for an "automatic"
way to switch between different antennas based upon
your current operating band. For that, check out
"Automatic Antenna/Amplifier Selection by Band" mods
elsewhere in this FAQ.
------------------------------
S:3.3. Microphones
------------------------------
Q:3.3.1 What is the best microphone to use with the IC-746?
In theory, your favorite microphone is the best choice,
provided you hook it up and adjust it properly.
Its basically just a matter of personal preference.
The confusion lies in the definition of "best".
Most users generally agree that the stock hand mic is
generally adequate for general use, but is not "best"
or "optimal" for any specific use. You know the tale;
jack of all trades, master of none.
If you want better transmit fidelity (or even broadcast
quality sound), then you'll want a full range microphone,
possibly with a dynamic element. Icom's own SM-20
gets good reviews for this application, as does Heil
Goldline microphones. Other microphones will also work;
these just happen to be the most popular.
Many operators have found that the inexpensive studio
microphones from Radio Shack work astonishingly well.
Yielding 90% of the performance at 10% of the price
makes this a viable, budget conscious, choice. It
also shows just how poor the stock mic is.
If you're after more "punch" for DXing or contesting,
then you'll want to look into one of the Heil DX
style microphones. They're frequency responses have
been tailored to accentuate the portions of the voice
spectrum that most contribute to understandability.
Their great performance have made them very popular.
For those of you who "want it all", Heil even makes
a microphone that switches both ways, literally.
It has two pick-up elements in the same mic, so you
can change between ragchewing and DXing punch at the
flick of a switch.
Who says you can't have your cake and eat it too?
------------------------------
Q:3.3.2 Can I hook up a different microphone directly to the IC-746?
Yes, but only if properly wired.
There is more to wiring up an external microphone than
just the differing pin-outs. You will also have to deal
with: DC bias, signal level, and impendence.
Icom uses electret elements and incorporate preamps
right into their hand mics. The DC power is fed directly
from the rig through the mic cable. If you are using a
different electret microphone, by sure it will operate
with the 8 Vdc bias. When using a dynamic microphone,
be sure you have a capacitor (value not critical,
around 1.0-4.7 uf) in the circuit to block the DC
supply voltage
Depending upon the microphone, you may have to use a
hefty amount of mic gain (and possibly compression as
well) to make up for the lack of the handset pre-amp.
You may even need to use an out-board microphone preamp
to get the signal high enough.
Finally, the Icom microphone input is at a relatively
high impendence (1-2K ?). A matching transformer (or
preamp) will yield the best results. Most microphones
operate at only 600 ohms impendence, and the impedance
mismatch will exacerbate the signal level deficiencies.
Some microphones operate at much higher impedances
(as high as 100K) and, unmatched, will suffer from
distortion in addition to signal level problems.
Since you're already wiring up a new mic cable, you
might want to short pins 6 and 7 with the chassis ground
to assure that they are at the same ground potential.
This often helps reduce RFI from coming in through
the mic cable.
------------------------------
Q:3.3.3 Can I use a Heil microphone with the IC-746?
Yes, most Heil microphones work well with the IC-746.
Bob does this himself.
As with any dynamic microphone, be sure you have a DC
blocking capacitor in the circuit to isolate the mic
element from the DC supply voltage Heil's pre-wired
mic harnesses are perfect for this.
A notable exception is the HS-706 which (as the sales
literature clearly states) ONLY works on the IC-706
series.
------------------------------
Q:3.3.4 How do I adjust the IC-746 for a Heil headset?
In theory, the IC-746 has enough microphone gain to use
an unaided Heil microphone. Heil's May, 2000, newsletter
discusses this topic, see:
http://www.heilsound.com/newslettermay00.htm
In short, you use moderate mic gain (50-75%, 12-3
o'clock position) along with moderate compression
(8-10db, 12-1 o'clock position) for the best results.
------------------------------
Q:3.3.5 Do I need a pre-amp to use a Heil microphone?
While the above procedure works for most rigs, it does
not seem to work for everyone. For the few that still
have gain problems, adding the Heil HMP microphone
pre-amp should work.
Some speculate that the differing mic gain requirements
are due to different versions of the IC-746, or simply
due to widely varying component tolerances. Nobody has
collected enough information yet to nail this issue down.
DO NOT use the HMP pre-amp unless you're sure you
need it. Too much gain will distort your transmitted
audio; with all the usual detriments (hard to copy,
splatter, etc...)
If you decide you need a pre-amp but want to build it
instead of buying it, then check out:
"Build a low cost Boost Microphone"
QST, Aug, 1989
along with the Icom specific mods available (DC blocking
capacitor, etc...) from KK5DR (Matt Erickson) at:
mailto:kk5dr@ev1.net
Another good QST article on microphone preamps is:
"Adapting the Astatic D-104 Microphone
for use with Modern Transceivers"
QST, Aug, 1999, p.34
a copy of which can be found at:
http://members.aol.com/ampmicro/
------------------------------
Q:3.3.6 What are the pin-outs on the microphone connector?
As listed on page 67 of the Instruction Manual:
1 - mic input
2 - +8V DC Output at up to 10ma
3 - freq up/down
4 - Main readout squelch switch
5 - PTT
6 - GND (PTT)
7 - GND (MIC)
8 - AF Out (varies with [AF]) (center pin)
------------------------------
S:3.4. Keyers
------------------------------
Q:3.4.1 Can I hook up my straight key to the front "Elec Key" Jack?
Q:3.4.2 Can I connect my own Electronic Keyer to the IC-746?
Q:3.4.3 How do I wire up my paddles for use with the internal keyer?
Short Answer
Yes, virtually any type of key/keyer can be connected
to the IC-746 via either the front "Elec Key" jack
or the back key jack. However, the two jacks require
different wiring, and only the front jack will give
access to the internal electronic keyer.
The front "Elec Key" jack on the radio accepts a
3-conductor 1/4 inch stereo phone plug and can be wired
for use with anything. The back "key" jack accepts a
2-conductor 1/4 inch mono phone plug and can be wired
for use with either a straight key or an external keyer,
but not for the internal keyer.
See page 68 in the operator's manual for wiring details
and pages 23 and 27 for the programming details.
Long Answer
FOR A STAIGHT KEY OR EXTERNAL KEYER:
For a diagram on how to wire the stereo plug see page 68
of the Instruction Manual. For a straight Key or keyer,
wire only the tip and the Sleeve, and leave the ring
as No-Connect.
tip ring sleeve
oooo ==== ]]]]]]} ---------> 2 cond wire to key/keyer
(+) (nc) (-)
The back "key" jack is a mono 1/4 inch phone plug and
is easy to wire.
When using the front Jack, You also have to set the
radio to recognize that the ring is not used. To set
the radio, You do have to go to the "key", "set"
menu and tell it you will be using a straight key.
See Page 23 and page 27 in the operation manual.
While in CW mode press KEY(F4), then press SET(F5),
Press the down arrow(F2) until you reach the sixth menu
(KEYER TYPE), Use the Main tuning knob to set the type
of keyer to "Straight Key".
TO USE THE BUILT IN ELECTRONIC KEYER WITH PADDLES:
Wire the 3cond Stereo plug (use the front jack) so
that the "Dit" is the tip, the "Dash" is the ring and
the sleeve is common(-). (You can also wire up a "bug"
this way (without electronic keyer))
oooo ==== ]]]]]]} ---------> 3 cond wire to paddles
(dit) (dash) (-)
To set the radio to use the internal electronic keyer,
You do have to go to the "key", "set" menu and tell
it you will be using paddles. See Page 23 and page
27 in the operation manual. While in CW mode press
KEY(F4), then press SET(F5), Press the down arrow(F2)
until you reach the sixth menu (KEYER TYPE), Use the
Main tuning knob to set the type of keyer to "Elec Key".
(or "bug Key" to use the bug without electronic keyer)
------------------------------
Q:3.4.4 Can I use the internal and external keyers at the same time?
Sure ... you can have an iambic keyer plugged into
the front, and a straight or external electronic
keyer plugged into the back. You can then use either
interchangeably.
We don't yet know of anyone brave enough (let alone
capable) to actually use both keys SIMULTANEOUSLY.
Would such an person be a "two fisted" operator? 8)
==============================
S:3.5. Amplifiers
------------------------------
Q:3.5.1 How do I hook up an Icom IC-PW1 RF power amplifier?
The electrical connections are easy, just follow the
diagram at the top of page 79 in your instruction manual.
Then carefully read the instructions that came with
the IC-PW1 because they can be confusing.
Icom has instructions for this on their WWW site at:
http://www.icomamerica.com/support/documents/pw1-746.html
They state:
1) Make sure the CT-17 is powered up. Connect
the CT-17 output 1 to IC-746, and output 2
to IC-PW1.
2) Power up the IC-746 and set up the CI-V
communication per the IC-PW1 manual. The
CI-V set up will vary between the early
and the latest IC-PW1 units.
3) Power on the IC-746 and the IC-PW1. The
IC-PW1 should now automatically select the
band the IC-746 is set to.
4) Now start the software, and set the software
com port setting to the port you have the
CT-17 connected to. The software should
recognize the IC-746 and show the exact
frequency on the computer screen the IC-746
is tuned to.
5) As you change bands on either the IC-746 or
the software, the IC-PW1 will follow that
band change. If you change bands on the
software, both the IC-746 and the IC-PW1
will follow that band change.
Paraphrased (thanks to WA0SXV), the procedure is:
Turn everything on, set the 746 to full power,
and key up in RTTY.
Adjust the ALC pot on the back of the PW1 to
set the IC-PW1 ALC meter to the mid-scale point.
Power out on the amp should now read around 500w if
you are using 110 or 1000w if you are using 220vac.
No adjustments are needed on the 746 --- the PW-1
ALC should take care of that. When properly adjusted
the power output scale on the 746 will read something
around 35-50w.
------------------------------
Q:3.5.2 What if I hook up more than just an IC-PW1?
The PW-1 manual claims that you will not have to mess
with the CI-V addressing. That's not always true.
If the IC-PW1 is directly connected to the IC-746 (on
default CI-V address 54h and 56H respectively) with no
other devices, then the PW-1 auto-config routine senses
the IC-746 and everything works just fine.
If you introduce additional devices or alternative
interfaces (such as the DX4WIN logging software using
the "$10 Radio Shack" interface, talking to the IC-746
in CI-V address 56H) then the PW-1 can become confused
and stop talking to the IC-746.
One solution to the problem is to set both the IC-746
and DX4WIN for CI-V address 54H - the same as the PW-1.
(But, shouldn't each device have a distinct address??)
------------------------------
Q:3.5.3 How do I hook up a non-Icom RF power amplifier?
Start by examining the diagram at the bottom of page
79 in your instruction manual, but be careful, it can
mislead you into some expensive mistakes.
The ground and antenna connections are just as
straight forward as they appear, no problems there.
Do not hook the SEND output directly to your amplifier
as shown. You will need an external switching relay
or circuit to avoid overloading the internal SEND relay.
Burning out the internal SEND relay is a common failure.
Not all amplifiers will have compatible ALC control
signals. The IC-746 ALC input runs from 0 to -4 Vdc.
W7DS designed a circuit to aid in automatic amplifier
band switching that may be useful to you. Check out the
"mods" section of this FAQ for more details.
------------------------------
Q:3.5.4 Do I really need an external amplifier switching relay?
Q:3.5.5 Where can I get an external switching relay?
Yes. If you hook up an external power amplifier, then
you will need an external amplifier switching relay or
circuit (see above). You have several to choose from:
Ameritron ARS 702
Ameritron ARB 704
MFJ ARB-702-I
MFJ ARB-704
W2ENY Amplifier Interface
Yaesu FRB-757
Users of older amplifiers (like the Heathkit SB-200)
will want to check out the "soft key" modules from:
http://www.harbachelectronics.com/
or a similar product, the AmpKeyer, at:
http://www.theheathkitshop.com/ampkeyer.html
Heil Sound makes a foot switch that can control both
PTT and amplifier switching, in the correct sequence.
http://www.heilsound.com/FS-2-Dual-Footswitch.htm
KD9SV has a "Front-End-Saver" switchers that handles
extra antennas along with the amplifier.
http://www.qsl.net/icom/download/fes.pdf
http://JohnJeanAntiqueRadio.com/gary.htm
------------------------------
Q:3.5.6 Why do I need an external amplifier switching relay?
Short Answer
Its far too easy to overload and damage the internal
switching relay, resulting in expensive and/or annoying
repairs. The external isolation relays are cheap
insurance for our rigs. Besides, even Icom technical
support reccomends them.
Long Answer
Given that the relay is prone to overload, the natural
question that arises is; just how much can it handle?
Things get both lengthy and muddy from this point
on, but since you're still reading, we'll press on.
Remember, you were warned.
This continues to be a process of discovery, so I'll
present what we know in that form.
# Instruction Manual
Page 79 of the instruction manual says that the SEND
jack is rated for 16 Vdc at 2A. Some rigs have failed
while well within those specs. Others seem to survive
conditions far in excess of that rating. Obviously,
the ratings in the manual don't tell the full story.
Homebrew explanations (and solutions for) the problems
abound. Some talk about bypass capacitors while others
talk about suppresion diodes. Folks debate inductive
vs resistive loads and ratings. Surge currents and
hot switching usually get brought up, as well as AC
vs DC loading. For years, the topic keeps coming up,
but with no consensus or dependable solution; except
that using an isolation relay/circuit seems to prevent
any overloads.
# Tech Support
So, many of us turned to technical support, but received
different answers at different times. For example,
in the icom@qth.net archives for January 2000, we
see that tech support told AB2BK that there was a
misprint in the manual. The true rating was 12 Vdc at
20mA and Icom reccomended an external isolation relay.
While that would explain the failures, it makes some of
the successes almost unbelievable. On the other hand,
the archives for February 2002 show that tech support
told N1JM that "The real scoop is UP TO 16V -OR- UP TO
2 amps.", again, reccomending an isolation relay.
While the techs did not agree upon the ratings, they
did agree upon using the external relay. Unfortunately,
none of the answers from tech support have adequately
explained the odd successes and failures.
# Service Manual
All of this boils down to how much abuse relay RL1271 on
the Main board can take. The parts list on page 6-12
shows the relay as an OMR-109F. The obvious solution
is to look up the parts and see what they are rated for.
As of January, 2002, nobody had reveiled any spec sheets
for the relay.
# Internet Search
Searching for "OMR-109" on the Internet did turn up a
curious tidbit. Icom has used the OMR-109 before, as the
SEND relay (RL2) in the IC-761. It had problems too.
There is a Service Bulliten (#24287-001A) entitled
"Larger relay for keying non-ICOM amplifiers" which
reccomends:
Replace RL 2 (currently labeled OMR 109)
on the PA Connector Board with a SY-12 relay
(ICOM P/N 921-04696). This relay is larger but
can be squeezed into place. Glue this relay
to the board with RTV.
Check out:
http://www.qsl.net/kd4sai/mods/icom/ic-761.txt
http://www89405.temp.w1.com/Modifications/B2502
More searching did turn up information for the SY-12-K
relay, which lists a contact rating of 1 A @ 24 Vdc or
0.5 A @ 120 Vac (resistive). We can infer that the
OMR-109 specs are most likely less than these.
http://www.fceu.fujitsu.com/pdf/sy.pdf
Unfortunately, we still do not have many answers.
# Contact Parts Supplers
Finally, in February 2002, we found a listing for the
OMR-109F (thanks to the kind folks at Omron Electronics
for helping out). It doesn't say much, but does show
a contact current rating of 1 A.
http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=14894&P=87296,91080,86600,76287,76437&M=PROP&N=1&LG=1&I=81&G=G
However, the above link did show who the manufacturer is.
OMR relays are made by OEG. That finally led to some
actual data sheets.
http://www.oeg.com.cn/pdf/14_OMR.pdf
http://www.qsl.net/kb9sss/IC-746/Parts/14_omr.pdf
Here are a few interesting pieces of info from the
datasheet:
Max. Switched Voltage: AC: 120V.
DC: 60V.
Max. Switched Current: 1A (OMR-F)
0.5A (OMR-H).
Max. Switched Power: OMR-F: 50VA, 50W.
OMR-H: 10VA, 10W.
Max. Switching Rate: 300 ops./min. (no load).
30 ops./min. (rated load).
Operate time: 1.0 msec
Release Time: 0.5 msec
Expected Mech Life: 100 million operations (no load).
Expected Elec Life: 1,000,000 operations (rated load).
First we see that the listed current/votage ratings do
not match anything we've seen or have been told before.
Curious that. Why has Icom technical support given out
at least TWO different sets of specs? One theory is that
the relay specs we have are still not detailed enough.
It turns out that there are two ways to report maximum
contact current. "Maximum Switched Current" is the
maximum current at switching time; when the contacts
are opening or closing. Once the relay is switched
on, the contact current may rise to as high as the
"Maximum Carrying Current", but must reduce again prior
to switching off. Thus, if the maximum carrying current
is 2A, then the answer from Feb-2002 could make sense.
# Switching Rates Explored
Closer examination of the maximum switching rates
reveils a possible problem. Suppose, for example,
I transmit at only 1 word per minute. We average 5
characters per word, 3 dit-dahs per character, and 2
switches per dit-dah. So, CW at 1 wpm will generate
30 relay operations per minute. That's the limit of
what the relay can handle at full load. 10 wpm will
generate 300 op/min, which is the no-load limit for
the relay. 30-40 wpm (what my local CW contesters do)
pushes us to about 1,000 op/min; which is well beyong
the relay's rating. The max internal keyer speed of
67 wpm (as per ARRL review) would yield a brutal
2,010 op/sec.
This could account for the varying results encountered in
the field. We'd all assumed till now that the problem
was simply one of current or voltage overload. Now we
can see that those operating QSK CW are overstressing
the part, no matter what the load. Pushing the part
that far beyond its operational limits would certainly
make it more failure prone, which could explain some
of the failures that have happened within the supposed
current limitations.
# Expected Lifetime?
Consider this: CW at 20 wpm would generate about 600
op/min, which would reach the expected mechanical
life of the part after less than 3,000 hours of
transmitting. But wait, if we apply that same rate
to the expected electrical life, we get less than 30
hours of transmitting time.
In contrast, AM/FM/SSB/RTTY operation would likely
require 200,000 to 2,000 hours (respectively) of
operating time to hit either expected lifetime.
# The Schematics
The schematic on page 11-4 of the Service Manual shows
the SEND relay as an AHY103, not the OMR-109F listed
in the Parts List on page 6-12.
(this is listed in the "Discrepancy" section of the FAQ)
Currently, we believe that the parts list is correct
and that the schematic is wrong. However, this might
help explain why Icom Tech Support has quoted different
specs at different times.
# Mysterious Successes
OK. To be totally fair, there are some amps out there
that seem to work OK without an isolation switcher.
Alpha Power, for example, uses an IC-746 daily to
test their Alpha 99 series of amplifiers. They report
no problems. Off course, their 25 Vdc exceeds Icom's
specifications but are within the relay specifications.
Go figure.
# Connection Confusion
So far, we've concentrated upon the SEND jack on the
back of the rig. There are also HSEND and VSEND signals
available via the ACC connectors. What makes matters
worse is when some folks mistake these signals for the
relay driven SEND line, when in fact they are driven
by transistor Q1302. The transistor is not a hardy as
the relay, with obvious consequences.
# Summary
We have now identified MANY possible failure conditions
for the SEND relay.
* Too much voltage
* Too much current (switching or carrying)
* V/C spiking from inductive loading
* Accidental AC operation
* Exceeding operational rate
* Exceeding expected lifetime
* Connection confusion
Those are the reasons for using an external SEND relay.
------------------------------
Q:3.5.7 My SEND relay seems to be stuck, what do I do?
Ultimately, you'll have to replace it, either yourself
or via Icom service.
It is possible (battle field repair) to free the contacts
by tapping the relay till it frees; but YMMV! Actually,
it takes a fair amount od disassembly to access the relay,
and this solution is temporary at best.
------------------------------
Q:3.5.8 Can't I just use the ACC port to key my amp?
An Icom IC-PW1? Yes. Any other amp? Not directly.
First off, the signal from the ACC ports is from an
internal transistor and will only handle a miniscule
load. An external switching circuit will be required.
The SEND jack (RCA phono connector) on the back of the
rig is relay operated and is output only. However,
the HSEND and VSEND signals that are available from
ACC1-pin-3, ACC2-pin-3, ACC2-pin6, and MIC-pin-5 are
all bidirectional. These leads go to ground through a
transistor when the rig transmits. Actively grounding
these leads will put the radio in the transmit mode.
You'll almost certainly need a solid state isolation
circuit of some sort for this to work correctly.
------------------------------
Q:3.5.9 How do I build my own SEND relay isolation circuit/relay?
Your design will be dominated by several basic
considerations: the voltage/load/polarity requirements
of your amplifier, your choice of SEND jack keying
or ACC port keying, and your choice of relay or solid
state switching.
The send relay in the IC-746 (and others) closes 10 to
11 milliseconds before the start of the RF and opens
about 7 milliseconds after the end of the RF. If you
use a relay between the rig and the amp it had BETTER
BE FAST. The relay in the amp needs to be closed before
the start of the RF. This means the amp relay AND your
intermediate relay together must be faster than 10 msec.
In general, solid-state systems tend to switch faster
than mechanical systems. However, the relay based
systems tend to be easier to design/build and are
more versatile.
The line used in the ACC port for this is a bidirectional
signal; it does both SEND and PTT functions. You'll need
to account for that in your design.
One example of a relay based design, complete with
suppressor diode, bypass capacitor, and limiting resistor
can be found at:
http://www.qsl.net/kk5dr/IcomKeyInterface.html
Rumor has it that Matt will even build it for you; for a
fee, of course. But then, you wouldn't have built your
own, would you?
One example of a solid-state design (originally intended
for a Kenwood, but easily adapted to an Icom) can be
found at:
http://www.qsl.net/k0bx/amp.html
Another example is here:
http://www.k6xx.com/radio/ic706amp.pdf
And yet another example:
http://www.yccc.org/Articles/AL1200relay.html
------------------------------
Q:3.5.10 Why do I get IC-746 birdies when I turn on my IC-2KL?
The IC-2KL is at fault, not the IC-746. The problem
is caused by a noisy, 12 volt switching supply within
the IC-2KL.
The supply is in a small shielded box on the top of the
chassis, behind the meter. Cleaning and tightening
the metal box and covers will help. Additionally,
Icom recommends changing out leaky bypass and filter
capacitors.
==============================
S:3.6. TNC
------------------------------
Q:3.6.1 How do I hook up a TNC to the IC-746?
Check out the wiring diagrams available at:
http://www.packetradio.com/tnc-to-radio.htm
==============================
S:4. IF Filters
------------------------------
Q:4.1 How many optional IF filters can I install into the IC-746?
There are two (2) slots for optional filters in the 9Mhz IF,
and one (1) slot for an optional filter in the 455Khz IF.
------------------------------
Q:4.2 What optional IF filters are available for the IC-746?
Available filters for the 9Mhz IF include:
Filter Bandwidth SF Typical Use
--------------------------------------------------
Inrad 121 250 hz 2.2 CW narrow
Icom FL-101 250 hz 3.0 CW narrow
Icom FL-232 350 hz 2.8 CW / RTTY narrow
Inrad 111 400 hz 2.3 CW / RTTY narrow
Icom FL-100 500 hz 2.5 CW / RTTY narrow
Inrad 320 1.800 Khz 1.5 SSB
Icom FL-223 1.900 Khz 1.9 SSB narrow
Inrad 110 2.100 Khz 1.5 SSB
Inrad 123 2.800 Khz 1.5 SSB wide
Icom FL-103 2.800 Khz 1.8 SSB wide
Available filters for the 455Khz IF include:
Filter Bandwidth SF Typical Use
--------------------------------------------------
Inrad 306 125 hz 2.1 CW narrow (might not fit)
Inrad 122 250 hz 1.8 CW narrow
Icom FL-53A 250 hz 1.9 CW narrow
Inrad 116 400 hz 1.7 CW
Icom FL-52A 500 hz 2.0 CW / RTTY narrow
Inrad 322 1.800 Khz 1.5 SSB narrow
Icom FL-222 1.800 Khz 1.7 SSB narrow
Inrad 314 2.100 Khz 1.5 SSB
Inrad 109 2.400 Khz 1.6 SSB
Icom FL-44A 2.400 Khz 1.75 SSB
Icom FL-96 2.800 Khz 2.0 SSB wide
Inrad 124 2.800 Khz SSB wide
Icom FL-257 3.300 Khz SSB wide
Notes:
The above specifications come from several sources, so
they might not be directly comparable. Also, there are
always variations from one manufacturing lot to another.
Use these figures only as a guide.
The Inrad 306 is listed on their WWW site, and is
electrically compatible, but might not fit in the
available socket.
The Icom crystal filters with an "A" suffix (FL-44A,
FL-52A, FL-53A) all have 6mm lower case heights than the
equivalent filters without the "A". Icom calls them
"low profile". They are electrically identical to
the taller filters. Nobody knows if there is enough
clearance to install one of the larger filters into
an IC-746.
There are apparently TWO slightly different FL-44A
filters. The earlier model has a slightly wider
bandwidth and steeper skirts than the later model.
No word yet on how to tell them apart.
While not an optional filter, W2ENY has a kit to modify
the IC-746 by replacing either the stock 9Khz or 15Khz
wide internal filters with a 6Khz wide filter. See the
"mod" question of the FAQ for more details.
------------------------------
Q:4.3 Which optional IF filters should I buy?
Better to ask, "Why would I even need filters?".
Quite possibly, you'll won't need any optional
filters. Use the Twin PassBand Tuning (TPBT) to
dynamically adjust your IF bandwidth first. Properly
used, TPBT can give you nearly any bandwidth you want.
You may decide that you don't need any anything else.
There are over a thousand possible combinations of
optional filters (1,539 at the last count). Most of them
will make sense (i.e. be useful) to someone, somewhere.
As it is a matter of style and situation, ultimately,
the choice will be up to you.
We've broken up this issue into several questions, each
targeting a more specific issue or problem. Short of
writing a book, it is the only hope of providing any
useful answers.
At the end of this section, we've listed some popular
combinations. Don't use a filter combination just
because it's popular. Optional filters could total
$500 or more. Understand what and WHY you're buying
to make sure you get your money's worth.
------------------------------
Q:4.4 What is an IF filter's "bandwidth"?
Q:4.5 What is an IF filter's "shape factor"?
Also called "passband", a filter's bandwidth is a
measure of how wide a signal will pass thru the filter.
For IF filters, this is typically measured as the span
between the filter's -6db points. (Some folks measure
bandwidth at the -3db points. Pay careful attention
to the specifications when comparing filters)
"Shape factor" tries to represent steepness of the
filter's attenuation curve. Typically defined as
the ratio of the -60db passband to the -6db passband
(bandwidth). The perfect shape factor of 1.0 is
unobtainable. Shape factors of 2.0 or less are
considered excellent.
This is one of those situations where a picture is worth
a thousand words. A good look at the spectral response
curve of a typical filter will make these terms clearer.
Inrad publishes basic performance curves of most of
their filters on-line. An example of a typical curve is:
http://www.qth.com/INRAD/graphs/116.gif
AB4OJ has a complete set of passband curves for Icom's
filters on his WWW site at:
http://www.qsl.net/ab4oj/icom/filters/filters.html
Several companies have good on-line treatments describing
basic filter characteristics, complete with diagrams.
Corning Frequency Control has a very concise page styled
in a glossary format at:
http://www.ofc.com/filters/definitions.html
(site not responding Jan-2002)
Vectron International also has a nice on-line treatment
of filter characteristics at:
http://www.vectron.com/products/xtal/filter.htm#definition
The folks at Piezo Technology Inc. describe filter
characteristics with attenuation curves.
http://www.piezotech.com/Technical_Information/techindex.htm
------------------------------
Q:4.6 Why do filter "bandwidth" or "shape factor" matter?
Narrower bandwidths reject more noise and improve
sensitivity. Wider bandwidths provide better fidelity.
Narrower bandwidths also reduce the number of
simultaneous signals the rig can "hear". This reduces
the AGC pumping action caused by nearby signals,
particularly important for CW and digital modes.
Smaller (tighter) shape factors reject more noise and
improve selectivity. Larger (wider) shape factors
generate fewer problems/complaints with fidelity or
ringing.
------------------------------
Q:4.7 What is considered to be a narrow filter?
In the context of (and for the purposes of) this
FAQ, a narrow filter is any filter that has a smaller
bandwidth than the stock 2.4Khz wide filters. However,
most texts will describe a filter as being narrow if
its bandwidth is smaller than that of the desired signal.
------------------------------
Q:4.8 What are narrow IF filters used for?
Usually, narrow filters are used to reject unwanted
signals or noise. The narrower the bandwidth, the less
noise there will be and the better the sensitivity.
You can lose part of the desired signal in the process,
but that may be preferable to the interference you're
trying to reject.
------------------------------
Q:4.9 Can an IF filter be too narrow?
Yes, an IF filter can be too narrow, but sometimes, that
can actually work to your advantage. We'll describe
only a few specific situations as examples.
When the IF filter's bandwidth is less than the bandwidth
of the desired signal, then part of the signal will be
rejected. This degrades the fidelity (quality) of the
received signal. In phone modes, the fidelity loss is
often mistakenly perceived or described by operators as
"distortion".
Fortunately, the inherent information redundancy of
human speech allows it to be readable even when an overly
narrow filter has rejected part of the desired signal.
That's where our advantage comes from.
One form of interference is when a nearby signal
overlaps your desired signal; as in an overcrowded band.
Rejecting the interfering signal necessarily rejects
part of the desired signal as well. Thus, the filter
is too narrow to allow all of the desired signal
to come through, but it is narrow enough to reject
the interference. While the result is "distorted" in
comparison to a clean signal, it is still more readable
than if you left the interference there.
Another example would involve CW or PSK31. The more
narrow the filter is, the less the interference and
noise. In these modes, it's almost impossible for a
filter to be narrow enough to actually reject part of
the desired signal, as in the previous phone example.
Instead, when a CW/PSK31 filter gets too narrow,
you start to experience the auditory equivalent of
tunnel vision. This can make it difficult to scan
around for signals.
One of the handy things about TPBT is that you can
narrow your effective IF filtering bandwidth at any time.
------------------------------
Q:4.10 What's the difference between IF filters from Inrad vs. Icom?
Inrad filters tend to have a superior shape factor to
Icom's (smaller numbers are better) as well as deeper
stopbands. They also tend to be cheaper.
When dealing with adjacent channel interference, the
filter shape (depth and slope of the attenuation curve)
is generally the prime factor. Inrad filters tend to
outperform the Icom filters for this application.
For example. The stock Icom filter in the 455Khz IF
has a -6db bandwidth of 2.4Khz and a -60db bandwidth of
about 5Khz. That gives it a shape factor of about 2.1
The comparable filter from Inrad has a shape factor of
1.6, a -6db bandwidth of 2.4Khz and a -60db bandwidth
of 3.8Khz.
This all means that the Inrad filter has a steeper
attenuation curve, resulting in better extraneous signal
rejection and improved selectivity.
The Inrad filters tend to have greater ultimate
attenuation than the Icom counterparts. Thus, Inrad
filters tend to do a better job of adjacent signal
rejection than Icom's filters.
However, while the 455Khz Inrad filters are drop-in
replacements for the Icom counterparts, the 9Mhz filters
are not. They need a short piece of coax and a connector
to wired up to the filter first. The adapting connector
plugs into the filter slot, thus alleviating any mods
to the radio itself. Reported assembly times range
from 1-4 hours per filter, depending upon the skill
and care of the installer.
Finally, some claim that there is an insertion loss
to the Inrad filters vs. the Icom filters. However,
it's been demonstrated that dropping the noise level
also drops the S-meter reading, possibly accounting for
the reports. Bench tests do not show any insertion loss.
Your ears may vary.
eHam.net has several user reviews on Inrad crystal
filters at:
http://www.eham.net/reviews/detail/1499
------------------------------
Q:4.11 Which IF should I put an optional filter into?
Realistically, the performance differences between
using filters in the 9Mhz IF vs. the 455Khz IF are fairly
small and will probably go unnoticed in normal operation.
Most people make this decision based upon slot
availability and filter cost.
------------------------------
Q:4.12 What's different between IF filters for 9Mhz vs. 455Khz?
455Khz IF filters tend to have superior performance
characteristics while 9Mhz IF filters tend to be
less expensive.
There are other differences (filter blow-by, ultimate
rejection, earlier roofing, etc...), but usually it all
comes down to cost. When money is no object, you'll
want to use one of each. On a tight budget, you'll
do fine with whatever you can afford.
------------------------------
Q:4.13 What are the 9Mhz IF filters best for?
When dealing with interference from nearby signals,
the sooner you reject the unwanted signals from your
RF chain, the better. So a single narrow IF filter
in a 9Mhz slot will sometimes outperform a single
filter in a 455Khz slot.
------------------------------
Q:4.14 What are the 455Khz IF filters best for?
455KHz filters tend to have superior shape factors
which seem to do a better job of eliminating background
noise and allow tighter adjacent channel rejection.
So a single narrow IF filter in the 455KHz slot will
sometimes outperform a single filter in a 9MHz slot.
------------------------------
Q:4.15 How do I get the best results from TPBT?
TPBT works best when the 9Mhz and 455Khz IF filters have
closely matching bandwidths. Non-matching bandwidths
will still work, but are less intuitive, which can
cause confusion.
There are several techniques to using TPBT. The one
described below has the virtue of simplicity.
Starting with both filters in their center, detented,
position (widest effective bandwidth), tune in your
desired signal as accurately as possible.
Grasping both IF shift knobs simultaneously, adjust for
the best sound. If you have a nearby, interfering
signal, then you'll probably have the best results
shifting your bandpass away from it.
Now, adjust just the 455Khz IF shift (the inner knob)
in the opposite direction for the best sound.
There's a whole document describing the theory and
mechanics behind TPBT at:
http://groups.yahoo.com/group/IC746/files/ic746_tpbt.txt
------------------------------
Q:4.16 How do I configure the IC-746 to use an optional filter?
After you've installed a filter, you need to tell
the radio about it. Using the SET menu, tell the radio
which filter you've installed (by Icom part number)
and which slot it is in. Then, hold in the FILTER
button for two seconds to bring up the filter selector.
Cycle through your available filters by mode and by
wide/narrow until everything is set up the way you want.
See the operator's manual for details.
------------------------------
Q:4.17 How do I configure the IC-746 to use a non-Icom filter?
You have to lie to the rig.
All of the IC-746 filter settings are on the basis of
Icom part numbers. (This is supposed to make things
easier for new operators.) Just tell the rig you've
installed the Icom crystal that most closely matches
the one you're actually using.
Lying to the rig does have a side effect.
The 746 cannot actually shift the IF filters' passbands.
Instead, the 746 shifts the LO frequencies of the 2nd
and 3rd IF stages to shift the signal back or forth,
aligning the edge of the desired signal with the computed
edge of the filter's passband.
Small lies generate small effects, like when you
tell the rig that a 2.1Khz wide filter is actually
1.9Khz wide, yielding a 100hz offset in the control.
Larger lies generate larger effects, like when you tell
the rig that a 400hz filter is actually 2.4 Khz wide,
yielding a 1,000hz offset in the PBT control.
------------------------------
Q:4.18 How do I use a CW filter in SSB mode to receive PSK31?
Icom took their ease of use one step further, and
programmed the rig to prevent the use of a CW filter
while in SSB mode; probably to prevent what they
considered to be a foolish user error. They didn't know
about PSK31 at that time. So again, you lie to the rig
during setup, telling it that the crystal is wider so
that the rig will allow you to select it for SSB use.
------------------------------
Q:4.19 Why is there only one optional 455Khz IF filter slot?
Nobody knows for sure, but the most popular speculation
is that it made the radio cheaper.
------------------------------
Q:4.20 Any tips on installing 9Mhz Inrad filters?
Neatness counts. Good soldering skills are a must.
Most of the hams who have installed one report that it
was more time consuming than they expected, but nothing
they couldn't handle.
KE5DC says, "Inrad also ships two socket pins that look
like they are to be used for the filter. This doesn't
work, as with the pins on the filter, the filter won't
fit in between the case and the fan. Solder the leads
etc. directly on the filter pins and then trim the
pins to prevent grounding. My first attempt the pins
had poked through the electrial tape and grounded to
the case. It initially seemed like the filter was more
effective than it should of been. Some playing around
with the filter settings while listening to a decent
signal narrowed down the problem to the 9MHz filter,
and I just redid it and it worked."
------------------------------
Q:4.21 Where do I install a 2nd Inrad 9Mhz IF filter?
According to K7ZL, the place Inrad tells you to put the
first filter is way over on one side in a little opening
next to a fan, and that works fine. But he has found a
second location. When you have the rig opened, if you
go on a line from the 9 Mhz filters, then to the 455
Khz filters, and keep on going towards the front panel,
you will see a square metal plate on the circuit board.
He mounted his second filter on top of the metal plate,
on its side, and it seems to work fine.
However, KE5DC reports that is is very difficult to
prevent the cover from coming into contact with the
filter. One could mistakingly force the cover closed;
putting stress on the circuit board causing failure at
some point in the future.
G0HDB has installed an InRad filter this way and can
confirm KE5DC's comment about the cover pressing on the
filter and thus stressing the circuit board. He overcome
this by slightly deforming the cover to make it clear the
filter; the deformation was done (very carefully!) using
the rubber-coated handle of a hammer! It only needs a
small amount of extra clearance so the deformation (a
very slight bulge in the cover) is barely visible - if
you didn't know it's there you'd probably never notice it
------------------------------
Q:4.22 Where can I find more information on filter characteristics?
Here are a few places on the WWW where you can find more
information on filter characteristics:
http://www.qth.com/INRAD/IC-756.HTM
http://www.qsl.net/ab4oj/icom/filters/filters.html
http://www.qsl.net/ab4oj/icom/passband/passband.html
http://www.icomclassic.com/tech_data/icom_filter_rev_a.xls
------------------------------
Q:4.23 What are some popular filter combinations?
"Popular" does not necessarily equal "best". Don't do
something just because it's popular. Read the above
material so that you can make an informed choice.
For example, one of the "best" optional filters for an
IC-746 is a 2.4Khz wide crystal filter for the 455Khz IF
(either the Icom FL-44A or the Inrad 109). The superior
characteristics over the stock ceramic filter probably
improves every one of the important receiver specs.
However, the filter is unpopular. Most hams simply
have trouble justifying $100-200 for a filter "they
already have".
Given that caveat, here are some popular filter
combinations you might want to ponder.
** None
** Single 500hz wide CW filter in either IF
** Dual 500hz wide CW filters, one in each IF
** Single narrow SSB filter in either IF
** Dual narrow SSB filters, one in either IF
** One wide CW and one narrow SSB filter at 9Mhz IF
Icom vs. Inrad? 455Khz vs. 9Mhz? Mostly a matter of
preference (read above) and probably not as important
as you think, otherwise, you need to read the more
detailed material above.
==============================
S:5. Computer Control
------------------------------
Q:5.1 How do I wire the IC-746 up for computer control?
Q:5.2 What cables do I need?
Q:5.3 What are CT-17, OPC-478, OPC-662 all about?
The IC-746 is computer controllable through a serial
interface, but it is not RS-232. This is both good
and bad. Bad, because you can't just plug it straight
into your computer (wrong voltages, etc...). Good,
because you can control four separate rigs with the
same serial line. Therefore, to connect the IC-746 to
a computer requires some interfacing. Icom made three:
the CT-17, OPC-478, and OPC-662.
The CT-17 is the full boat. Versatile, it will allow 4
rigs to be controlled by a single RS-232 serial line.
It's also the most expensive option and requires
external power.
If all you want to do is connect up a single rig, then
Icom's WWW site lists the OPC-662 remote PC control
cable as the official part. If you can find it,
then great. Most people can't. Instead, many hams
have successfully used the OPC-478 PC cloning cable.
It's less than half the cost of the CT-17. However,
it is very short (1 ft ?) and will require a 1/8 inch
stereo to mono plug adapter for use with the IC-746.
When you buy the RS-746 remote control software from
ICOM, it comes with a single rig cable (OPC-662 or
OPC-478?).
W2ENY sells a complete CT-17 clone and a single rig
cable. They're both more complete package than Icom's,
coming with cables and software resources on a CD-ROM.
They're also cheaper. You can find out more at:
http://www.geocities.com/w2eny/civ/
http://www.geocities.com/w2eny/icom_cable/
You could purchase the nearly universal rig interface,
the RigBlaster, from the folks at West Mountain Radio.
It does a lot more than simply computer control, and
is adaptable to other manufacturers (for a price).
http://www.westmountainradio.com/
The Raymond Sarrio Company also make transceiver to
computer interfaces:
http://www.sarrio.com/sarrio/w1gee.html
There's really not that much circuitry in "simple"
interface cables, and many have homebrewed them for as
little as $10. Supposedly, the November 2000 issue
of QST has a suitable design (with feedback in the
January 2001 issue). On-line circuit diagrams based
on the QST article appear at:
http://www.ambersoft.com/Amateur_Radio/Icom_Interface.jpg
and
http://www.qsl.net/civ_commander/interface.jpg
KD6UU posted detailed schematics and instructions
on eham.net:
http://www.eham.net/articles/1588
and then wrote an excellent updated follow-up article at:
http://www.qsl.net/kd6uu/icomci.html
The actual design of the interface circuit is subject
to debate (as the above link will make clear). Several
alternative designs (along with a wealth of related
information) are available from DF4OR's WWW site at:
http://www.plicht.de/ekki/civ/
A few other sources for CT-17 circuit information are:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/CIVInterface.htm
http://www.oz1eqc.dk/Downloads.htm
http://www.g3vgr.co.uk/civ.htm
The OZ1EQC version of the circuit allows the use of
the same COM port for both CT-17 control and RTS style
keyer control. The software configuration implications
are left as a puzzle for the reader.
When building the G3VGR version, AD6ZU makes the
following observations:
I found that the G3VGR interface to be quite easy
to build inside the DB-9 shell. The parts are
cheap and it's quite tolerant to using components
not listed on the schematics. I used 2N3904's
instead of 2N2222's because they were what I had.
I also used 5.1K resistors instead of 4.7K and had
no problems with the interface. I've built about
a half dozen so far and the suggestions I have for
this interface are:
Start with the shortest connections (the shorting
of the pins).
Imagine working from the connector toward the back
of the shell. This makes for a much neater layout
than randomly building the circuit "ugly style".
You can practice by builting your first interface
that way since the parts are so cheap it's easy to
build another one.
Physically stack the two transistors atop each
other with the two emitters twisted together.
This helps to keep the volume down.
A little heat shrink tubing may help here and there,
but use it very sparingly, it adds volume and a
smart layout really doesn't require any.
Use a highlighter to trace out the connections
you've made. It's easy to get mixed up as to which
connection you've made and which ones you haven't.
Be sure to strain relief the cable in the shell.
An inadvertant tug on the cable can pull a connection
loose or cause a short circuit (nothing will "burn
out", you'll just lose the communications and start
pulling your hair out).
When you complete the interface, if it doesn't
work, recheck your connections and follow the
schematic again. The design REALLY DOES WORK.
Most likely, there was a mistake in the soldering.
You can also purchase many renditions of these hardware
interfaces from a variety of sources:
### Universal RS232 Serial Interface for Icom/Yaesu
http://www.butel.nl/icomr2/icom11.html
### K1NU ICOM Computer Control Interface
http://home.att.net/~k1nu/k1nu/Products/
### RTS-01 Computer Interface cable for Icom HF Radios
http://rtsars.com/othercables_template.cfm
http://www.sarrio.com/sarrio/w1gee.html
------------------------------
Q:5.4 Do I need a special cable to connect a CT-17 to an IC-746?
No - the cable is a simple 2 wire cable with a 1/8"
miniature phone jack on each end. When homebrewing,
some folks don't even bother to shield the cable and
just use a twisted pair.
------------------------------
Q:5.5 What is the control protocol for the IC-746?
Q:5.6 What is CI-V?
CI-V is the control protocol used by ICOM for remote PC
control of their equipment.
This feature was originally used to enable a separate
transmitter and receiver to act as a transceiver when
interconnected via the CI-V bus (the receiver acts
as a "slave" to the transmitter's QSY and mode-change
reports) and for external amplifier control. It was
only natural to adapt it to computer control.
The basics of the protocol are documented in the IC-746
Instruction Manual on pages 74-75. However, most people
will prefer the documentation available from DF4OR's
WWW site at:
http://www.plicht.de/ekki/civ/
or the documentation that comes shipped with W2ENY's
control cables:
http://www.geocities.com/w2eny/civ/
http://www.geocities.com/w2eny/icom_cable/
W7FG Vintage Manuals has listings in their catalog
for both the CT-17 Level Converter and for the CI-V
Communications Interface on their WWW site at:
http://www.w7fg.com/
------------------------------
Q:5.7 What is the CI-V address of the IC-746?
The CI-V address of the 746 is $56 (hexadecimal).
------------------------------
Q:5.8 What computer software is available?
Q:5.9 Where can I get computer software and upgrades?
There are several choices (compromises?) available.
On one end of the spectrum, we have programs that
replicate nearly all of the IC-746 controls on the
computer. On the other end, there are programs that
do computer assisted contact and contest logging.
There is a fairly comprehensive listing of CI-V
compatible software on DF4OR's WWW site at:
http://www.plicht.de/ekki/civ/
We'll mention some of the available software options
below. User reviews for some of the below software
can be found at:
http://www.eham.net/reviews/
and
http://www.qrz.com/search.pl?topic=reviews
** Icom RS-746 software
Icom SELLS a program called RS-746; buying it
is certainly the path of least resistance. It is
available through the usual retail channels. It comes
complete with both software and the necessary cabling
(OPC-662?). Many people describe it as a thing
of beauty. (Of course, beauty only runs skin deep.)
A description of the software can be found at:
http://www.icomamerica.com/amateur/hf/746soft.html
To quote ICOM's own support FAQ (circa May 2001):
Q: Where can I download the ICOM PC programming (or
cloning) software?
A: The ICOM programming software is not freeware,
and is not available for download on our Web site,
or anywhere else on the Internet. It must be
purchased either from an authorized Icom America
dealer, or direct from ICOM. RT Systems also
develops programming software for ICOM radios.
Ray (the product manager at the 2001 Hamvention) was
very firm on this issue. They take a dim view of the
pirated copies available on the internet.
Last word we know of (January 2001), Icom had no plans
to update/fix/enhance the RS-746 software.
** RT Systems software
OK, so Icom refers us to RT Systems at:
http://www.rtsars.com/
However, as of May 2001, RT Systems does not have a 746
control program. They told N8AVX (in February 2001)
that they had no plans to do so either.
** Kingsmith Software
Kingsmith Software is developing control software for
the IC-746 (RATS IC-746), but as of May 2001, it wasn't
available yet. More information is available at their
WWW site at:
http://www.kingsmith-software.com/
** W2ENY
W2ENY ships a CD-ROM with lots of software and
documentation along with the PC to rig interface cables
he sells. Many of the packages listed here are also
on his disk.
http://www.geocities.com/w2eny/civ/
http://www.geocities.com/w2eny/icom_cable/
** RadioComm
Arachnophilia has several programs: RadioComm,
IcomControl, and EasyTuner (among others). Check out
the download section on their WWW site is at:
http://www.arachnoid.com/
** YP Log
Tony Field (VE6YP) makes a radio control and logging
program called YPLOG that can control up to 4 rigs at
a time and supports logging and contesting. His WWW
site is at:
http://members.shaw.ca/ve6yp/
** TRX Manager
Some say that TRX Manager by F6DEX has more features
than the original radios. More info can be found at:
http://www.trx-manager.com/
http://www.hosenose.com/trx-manager/
** XMLOG
The freeware logging software produced by W1ECT also
talks directly to the IC-746. You can learn more at
either the WWW site:
http://www.xmlog.com
or at the yahoo e-mail group site at:
http://groups.yahoo.com/group/xmlog
** TR Log
One of TR-Log's claims to fame is that it will run on
just about any PC. More details at:
http://www.qth.com/tr/
** CI-V Commander
A package that integrates well with the DxLab software
suite. More details at:
http://www.qsl.net/civ_commander/
** IRC
One of IRC's claim to fame is selectable skins.
You get to choose what you want your radio to look
like, be it IC-746, IC-706, or even a 007 spy watch.
More details at:
http://n9zle.tripod.com/
** ScanCat
Very extensive scanning support, including automatic
digital recording to your hard disk,
http://www.scancat.com/
** Radio Manager
An example of the virtue os simplicity, this shareware
from KC5IRJ does a lot with minimal resources.
http://www.interplaza.com/bensware/rmm32.htm
http://www.leader.it/shareware/info/00088.html
** Zakanaka
This (and a logger) was written by K4CY:
http://www.qsl.net/kc4elo/
** Icom Pro Memory Edit.
Small program that allows editing and organizing all
of the memories in any of the 746/756 series.
http://www.plicht.de/ekki/software/pme.html
** MixW
http://tav.kiev.ua/~nick/mixw/mixw.htm
------------------------------
Q:5.10 Why doesn't computer software update freq when tuning the 746?
CIV Transceiver, when enabled, forces the radio to
report its frequency whenever you QSY, and to report its
mode whenever you change mode via a front panel button.
Make sure you've set this option in the IC-746 if your
software supports it.
With CIV Transceiver not enabled, rig control software
must periodically "poll" the radio to determine its
current frequency and mode. When using this mode,
make sure you have set your software's polling rate
accordingly.
------------------------------
Q:5.11 How do I wire up the IC-746 for use with PSK31?
The simplest way is to buy an interface. There are
several available, some examples are:
BUX CommCo http://www.buxcommco.com/
Donner's Digital http://home.att.net/~n8st/
West Mountain Radio http://www.westmountainradio.com/
Or, you could build an interface. You'll need audio-in,
audio-out, and PTT signals. Several DIY plans are
available:
http://www.qsl.net/wm2u/interface.html
http://www.qsl.net/wm2u/psk31.html
http://www.arrl.org/tis/info/HTML/psk31/index.html
http://www.w5bbr.com/soundbd.html
http://home.teleport.com/~nb6z/psk31.htm
http://www.psk31.com/Hook_it_Up/hook_it_up.htm
------------------------------
Q:5.12 Why isn't my computer control working?
There are MANY things that could be wrong. Here are
a few of the things you can check:
* Computer's serial port baud rate
* Computer's serial port address
* Interconnect wiring
* Make sure the 746 CI-V address (#28 in the 746 menu)
is set for "56h".
* Make sure the 746 CI-V baud rate (#27 in the 746 menu)
is set to "AUTO".
* Make sure the 746 CI-V Transceive (#29 in the 746 menu)
is set to "ON".
* Make sure the 746 CI-V 731 Mode (#30 in the 746 menu)
is set to "OFF".
==============================
S:6. Problems and Clarifications
------------------------------
Q:6.1 What's that funny rattling noise I hear when I first power on the rig?
Often, its the antenna tuning unit. The relays make
audible clicking/rattling sounds.
------------------------------
Q:6.2 What's that "click" I hear as I tune across certain frequencies?
The clicking noise you hear is very likely from the
relays for the rig's preselector (the service manual
calls them RF filters). At each boundary point, the rig
switches in a different RF filter. There are several:
0 - 1.6 Mhz low pass
1.6 - 2 Mhz band pass
2 - 4 Mhz band pass
4 - 8 Mhz band pass
8 - 11 Mhz band pass
11 - 15 Mhz band pass
15 - 22 Mhz band pass
22 - 30 Mhz band pass
30 - 50 Mhz band pass
50 - 54 Mhz band pass
54 - 60 Mhz band pass
108 - 174 Mhz band pass
Some mistakenly call this the antenna tuner (there is
even some component overlap), however, the preselector
and tuner serve different purposes and are each switched
in and out accordingly.
------------------------------
Q:6.3 Why doesn't the ALC meter work while adjusting the "mic gain"?
Despite what the manual says, the ALC meter only works
for SSB; not FM, CW, or RTTY. Nobody knows what (if
anything) the ALC reading means on the other modes.
------------------------------
Q:6.4 Why can't I program any numbers into the memory names,
the CW memory keyer, etc...?
Use the keypad to enter numbers. The dial only does
letters and punctuation.
------------------------------
Q:6.5 How low can the IC-746 supply voltage be?
Well, page 69 of the Instruction manual says the supply
voltage can range from 12 - 15 Vdc. Whereas, page 84
says 13.8 Vdc +/- 15%, which is about 11.7 - 15.8 Vdc.
Despite what the manual says, some IC-746's run at
voltages as low as 11.0 Vdc. The highest "drop-out"
voltage reported so far has been 11.4 Vdc.
Be aware, that while the IC-746 will operate at lower
voltages, it does so at reduced power. The power roll
off starts at about 13.4 Vdc, as evidenced from the
measurements shown at:
http://groups.yahoo.com/group/IC746/files/IC746-Power.jpg
------------------------------
Q:6.6 Why isn't my output power up at 100 watts?
One possibility is your DC supply voltage.
As shipped, the IC-746 really wants a full 13.8 Vdc to
yield full output power. While the rig can operate at
voltages as low as 11 Vdc, power starts dropping off
as soon as you drop below 13.5 Vdc. Check the actual
voltage your rig is receiving. You may need to adjust
the voltage setting on your power supply.
If your rig isn't getting the voltage you think it
should, then check for voltage drops along the power
cord as well as across joints, fuses, and connectors.
It's possible to lose as much as a half volt per
connection. Solder joints and use high quality
connectors where possible.
12 AWG wiring is the minimum, but 10 AWG is better.
Some in-line fuses have had their solder end caps
oxidize, thus interferring with current flow and
dropping the voltage.
If you absolutely can't get your voltage up (for example,
total battery power), then you might consider adjusting
the power settings for the RF PAs (there are 4 of them).
However, trying to run a full 100w output at the reduced
voltage will most likely degrade the quality of your
transmitted signal (clipping, IMD, etc...). Most hams
decide that the 1-2db gain doesn't justify the crumby
signal.
One last possible remedy for the low voltage problem.
You could get a DC-DC voltage converter. These are also
called voltage boosters. Such a device accepts 12Vdc
in and yields 13.8Vdc output. There's a price. First,
they tend to only be 80-90% efficient, so a 20A draw
by the IC-746 can translate to a 25-29 amp draw by the
converter. Secondly, commercial units like the Newmar
12-12-35I DC-DC Converter can retail for more than $900.
There is a more afordable, ham designed and built,
voltage booster system from W4RRY that should do the
job. Check out:
http://www.fastq.com/~w4rry/
------------------------------
Q:6.7 The backlight in my LCD has stopped working. What's wrong?
Short Answer
Its probably one of the display driver transistors on
the S-Logic board behind the display. It will have to
be replaced.
There is reason to believe (but no proof) that setting
the LCD brightness to HIGH may reduce the failure rate.
Long Answer
Unfortunately, this has become a problem for many
746 rigs, as evidenced by the data collected at:
http://groups.yahoo.com/group/IC746/database?method=reportRows&tbl=2
It's not the actual 'lamp' itself, but one of the
driver transistors. The lamp is fluorescent, and will
probably never wear out. Even if it did, the lamp isn't
available as a separate part; it's part of an assembly
you need to get from Icom.
# Background into problem
There is a DC/AC converter driving the "lamp".
Check the S-Logic board for transistors Q301, Q302,
Q303, and Q304. Q302 is usually the culprit as it
is the voltage/current regulator for the dimmer
function. If you have a DC voltage on the collector
which is variable by the dimmer function on the radio,
then this transistor is probably OK. Q303 and Q304 are
the next most likely candidates. These 2 transistors
are in push-pull configuration to drive the X-former
(base is 180deg phase shift by the X-former)
Refer to pages 6-1, 9-1, 10-1, and 11-2 in the "Service
Manual" for more details.
Several folks at:
http://groups.yahoo.com/group/IC746
have successfully performed these repairs themselves.
OZ5ACI feels that the way the Q302 transistor is mounted
is a design flaw. Icom used the cooling fin of the
transistor as a soldering point, thus if it gets too
hot, the solder might melt. That slowly deteriorates
the soldering material resulting in a lost connection
and a cooked transistor. He has a feeling that future
cooked transistors can be prevented by simply unsoldering
the transistor cooling fin to lift it and lengthen the
center leg to establish connection at the cooling fins
soldering point.
AH6LE counters that if the transistor gets hot enough to
melt solder (300 degrees or so), then there are other
more serious problems. Most solid state devices won't
survive such temperatures, thus we're seeing the result,
not the cause.
# The repair
One of the techs at MTS (a company that repairs Icom
gear) told K8UT that the repair is not difficult,
but he does not recommend it to those without
soldering/desoldering experience. The repair involves
disemboweling the rig to get the S-logic board out;
removing a metal shield that covers the transistors
(about six solder connections); and then replacing the
surface mount transistor. And, of course, reversing
the whole process to put the rig back together again.
The part itself is cheap - around $3.00 (Feb-2002).
If you're tempted to unsolder the control pots from the
S-Logic board, stop and think; you're probably doing
things the hard way. The affected transistors are on
the side of the board facing the front of the radio.
More extensive "mechanical" disassembly will eventually
gain you access. Start by removing the front panel
and work your way back. Page 7-2 of the Service Manual
should help.
Icom UK told GW3WSU:
"The transistor (Q302) is available from stock
but is a 2SB1201, it is only 47p + carr and vat,
but unfortunately is below out 10 minimum
order charge. You do not have to unsolder
the pots, remove the plastic front panel,
then undo the pot fixing nuts from the metal
sub-chassis, and it should all just come away.
When you come to replace the transistor, its
best to remove the screening can, this gives
better access to the de