Fellow Aviators, ICOM did at least respond to my latest post(below) however, They still do not address the issue I raise of microphone impedance matching. Where are my electronic techies? I ask for your feedback and support.
Thank you
Walt.
===================================
My post back to ICOM, with thread below:
Mike Hilton,
Thank you for responding.
I have it in my notes that we spoke on 15 Nov 2010. Please refer to ABHI215195, ABHI1651A4, & AC9G412126.
MH:“Not all radios and headset combinations have issues with RF feedback
that you mentioned.”
WRP:>> Mike, I did not specify RF feedback; You have assumed RF feedback. But continuing the discusison; you are correct in that some headsets do work, I have one headset (Sigtronics S-45) that does appear to work with my A24/opc499. However, my other two (a FlightCom Classic 40XL, the third is in the aircraft so I do not have the model here) do not**. The most critically for my application the A24 exhibits oscillation in the mic circuit with my Sigtronics SPCC-2 intercom in line. Yet all three of my headsets work when individually mated with my panel radios in my aircraft, and all three of my heads sets work in all combinations with the SPCC-2, and all three headset work in combination with the SPCC-2 and the aircraft radios. The only issue is “pickiness” about the A24’s mic tolerances.
** (not an RF feedback as this has been tested with the A24 terminated properly in to a non-reactive 50 Ohm load (can-tenna)).
MH: “Also, Icom America can only support US products and
the "E" designation indicates that this is a European radio. “
WRP:>> Mike, I forwarded the post regarding the “E” model from a forum, my A24 is the north American A24 purchased directly from the ICOM booth at the EAA fly-in at KOSK Wisconsin USA.
>>>>POINT: I am not alone in experiencing non-RF feedback issues, and
>>>>POINT: both the north American and European manuals specify a mic impedance of >100,000 Ohms. This is not consistent with general aviation. Please research TSO -C139 >>>> RTCA/DO-214, Audio Systems Characteristics and Minimum Performance Standards for Aircraft Audio Systems and Equipment, dated March 2, 1993.
>>>>POINT: ICOM is selling an aviation product which is not designed to the commercial standards of general aviation. {Please check other manufactures, and your own [ICOM] A14,A23, & A210 aviation products; the listed mic impedances are 150, 150 and 600 Ohms respectively. }
MH: “That being said, you may still be able to use the information on our web site in
the Knowledge Base. To get there, first go to our home page at:
www.icomamerica.com and then, click on "Support". Next, click on
"Knowledge Base" and you will see a search engine on the following page.
In the field labled "KB Number", type in this number: 64AJ571413 and
click on the "Go" button. Click on the link under "Attachments" and you
will see a solution to this issue. I hope that this will help.”
WRP:>> Thank you, however, this was the solution given to me a year ago, and twice more by your offic and now yet again::: I installed the ferrite beads over a year ago, and again emphasize that the oscillation persists even on bench checks when the RF was properly terminated into a non-reactive non-radiating resistive load and the RF benign environment was confirmed with a spectrum analyzer and signal strength meter.
SO…. Talk to me about mic circuit designs, and impedance matching…
1.) Please confirm that your manuals are correct in stating the A24 has a mic impedance of >100,000 Ohms.
2.) Please confirm to me that you have verified general aviation microphone impedances standards and state you findings. (Check my earlier posts, I’ve already summarized my findings and sent them to you)
3.) Given a miss match of say 50, 150, (470 ohms driven with 8 to 16 vdc might be ideal?) or 600 Ohms to 100,000 Ohms, what would an electronics engineer predict? ?? A circuit so far out of match that it will not function and in some cases produces an oscillation? Yet a few headsets with a 2K or so impedance might provide enough loading to function….?
4.) If this is beyond your expertise or your authority to comment please have an engineer or management respond.
V/r
Walt
----- Original Message -----
From:
[email protected]
To: "walt peterson15" <
[email protected]>
Sent: Friday, December 10, 2010 11:20:45 AM
Subject: ICOM Technical Support Ticket # AC9G412126
Good Morning.......
Thanks for your e-mail.
Not all radios and headset combinations have issues with RF feedback
that you mentioned. Also, Icom America can only support US products and
the "E" designation indicates that this is a European radio. That being
said, you may still be able to use the information on our web site in
the Knowledge Base. To get there, first go to our home page at:
www.icomamerica.com and then, click on "Support". Next, click on
"Knowledge Base" and you will see a search engine on the following page.
In the field labled "KB Number", type in this number: 64AJ571413 and
click on the "Go" button. Click on the link under "Attachments" and you
will see a solution to this issue. I hope that this will help.
Best Regards;
Mike Hilton
Technical Support Representative
ICOM America, Inc.
2380 116th Ave. NE
Bellevue, WA 98004
Ph. (425) 454-7619
Fax (425) 637-8417
Walter Peterson
[email protected]
Description
EMAIL
BODY: Carl, Fred, Mike,
Below is a post I remember seeing and found again. It seems I am not the
only ONE!
Walt
============================================================ ============
=
Has anyone got one of the new Icoms to work with a headset?
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I am in the market for a handheld transciever for use in our Chippy, so
bought an Icom A-6E with OPC499 haedset adaptor. Worked fine without the
headset, but on fitting the OPC499 and headset, it just gave feedback
whistle on transmit. So I took it back to the dealer.
He got another A-6E out of stock, another OPC499, and a new headset -
same result. Tried different headsets - same result. Same OPC499 and
headsets worked fine with an A-3 transceiver the dealer had in stock.
I got a refund from the dealer, and e-mailed Icom who said they were
aware of the problem (RF feedback) and had a fix. Someone off the
'Flyer' forum who had the same problem had Icom apply the fix to his
A-6E. But when he got it back, it still had the same problem.
Has anyone out there got an A-6E or A-24E that works OK with a headset?
SSD