Any problems: headsets to handheld?

[Michael Horowitz]

Folks - I'm having difficulty getting audio from my Avcomm headset to
my Icom A-21 handheld.
The Icom requires a condenser microphone and the Avcomm has an
'electret' element, which as I understand is a variety of condenser
mic.
Has anyone had a similar problem and how was it solved? - Mike

PS- I see a variety of circuitry on the 'net describing how to power
the microphone, but I was hoping not to have to go off building
another box.

[Ed Sullivan]

Michael Horowitz > wrote in message >...
> Folks - I'm having difficulty getting audio from my Avcomm headset to
> my Icom A-21 handheld.
> The Icom requires a condenser microphone and the Avcomm has an
> 'electret' element, which as I understand is a variety of condenser
> mic.
> Has anyone had a similar problem and how was it solved? - Mike
>
> PS- I see a variety of circuitry on the 'net describing how to power
> the microphone, but I was hoping not to have to go off building
> another box.

Michael, I had problems with my Avcomm headset's mike and sent it back
to the factory for repairs which they did and returned it. It then
would not work with my STS handheld. I called them and they asked what
radio I was using.
I told them and they said that they had replaced the element in the
mike width a newer version and that it worked well with an in dash
radio, but not with a handheld. I returned the headset and they put in
the older model element. It works fine now.

Ed Sullivan

[Mike Weller]

On Fri, 26 Sep 2003 05:00:26 -0400, Michael Horowitz
> wrote:

>Folks - I'm having difficulty getting audio from my Avcomm headset to
>my Icom A-21 handheld.

Your Icom A-21 uses an internal electret mike. There is no reason
your headset electret won't work. I use my headset with an A-3 and it
works fine. Are you sure you're putting the mike about a half inch
from your lips and speaking directly into it?


>The Icom requires a condenser microphone and the Avcomm has an
>'electret' element, which as I understand is a variety of condenser
>mic.

Not true, see above.

>Has anyone had a similar problem and how was it solved? - Mike
>
>PS- I see a variety of circuitry on the 'net describing how to power
>the microphone, but I was hoping not to have to go off building
>another box.

Just not true. The only headset interface that I've seen that
requires power is for active noise cancellation.

Mike Weller

[Michael Horowitz]

Mike - thanks for the reply, but I believe we may be miscommunicating.
First off, per ICOMAmerica's service desk, the A-21 uses a condenser
mike. He didn't say electret and because the A-21 is old, probably
isn't an electret element. And talking into the body of the handheld
works fine, as does the accessory "speaker/mic" - however, please note
we are talking about neither. We're discussing the problem of
connecting the AvComm AC-450 to the A-21.

Second, the electret mike element does require power for the FET
contained therein (this may be the root of my problem; OTOH, if the
'speaker/mic' works, then power is coming from somewere!)

">Not true, see above." - I'm not sure what we're disagreeing on.

Condenser mics and electret condenser mics both require power.Granted,
for different reasons. My source for that statement is based on the
following URL, but also on other reading concerning how condenser mics
operate:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/Microphone.htm

Would you consider the use of the word "incorrect" vice the phrase
"not true". "Not true" has the implication the other person is
intentionally making a misstatement. I'm sure if we were face-to-face
the problem wouldn't exist. - Regards, Mike





Mike Weller > wrote:

>On Fri, 26 Sep 2003 05:00:26 -0400, Michael Horowitz
> wrote:
>
>>Folks - I'm having difficulty getting audio from my Avcomm headset to
>>my Icom A-21 handheld.
>
>Your Icom A-21 uses an internal electret mike. There is no reason
>your headset electret won't work. I use my headset with an A-3 and it
>works fine. Are you sure you're putting the mike about a half inch
>from your lips and speaking directly into it?
>
>
>>The Icom requires a condenser microphone and the Avcomm has an
>>'electret' element, which as I understand is a variety of condenser
>>mic.
>
>Not true, see above.
>
>>Has anyone had a similar problem and how was it solved? - Mike
>>
>>PS- I see a variety of circuitry on the 'net describing how to power
>>the microphone, but I was hoping not to have to go off building
>>another box.
>
>Just not true. The only headset interface that I've seen that
>requires power is for active noise cancellation.
>
>Mike Weller

[Ed Sullivan]

"karel adams" > wrote in message >...
> "Michael Horowitz" > schreef in bericht
> ...
> > Folks - I'm having difficulty getting audio from my Avcomm headset to
> > my Icom A-21 handheld.
> > The Icom requires a condenser microphone and the Avcomm has an
> > 'electret' element, which as I understand is a variety of condenser
> > mic.
>
> Don't be confused.
> Electret is one technology to produce condenser mikes
> and it is the only one suitable for aircraft use.
> Sorry I can't help beyond this little clarification.
> KA

Rather than indulge in all these expert debates, I think I would call
AVCOMM and see if they can offer some help.
Ed

[Barnyard BOb --]

On 27 Sep 2003 09:56:44 -0700, (Ed Sullivan) wrote:

>"karel adams" > wrote in message >...
>> "Michael Horowitz" > schreef in bericht
>> ...
>> > Folks - I'm having difficulty getting audio from my Avcomm headset to
>> > my Icom A-21 handheld.
>> > The Icom requires a condenser microphone and the Avcomm has an
>> > 'electret' element, which as I understand is a variety of condenser
>> > mic.
>>
>> Don't be confused.
>> Electret is one technology to produce condenser mikes
>> and it is the only one suitable for aircraft use.
>> Sorry I can't help beyond this little clarification.
>> KA
>
>Rather than indulge in all these expert debates, I think I would call
>AVCOMM and see if they can offer some help.
>Ed
+++++++++++++++++++++++++++++++++

Yeah...
Kind of a 'dead' issue, Ed. (8-D


Barnyard BOb --

[RDA]

Everyone is trying to provide a technical solution. Kudos.

Now just go out and buy (or try to find a used one, which is more like it)
the HS61(? I think- mine's in the flite bag) headset adapter that Icom made
for interfacing aircraft headsets with the A21. Works great, but that was
the biggest problem with an otherwise good aviation band radio- all my Icom
ham accessories work fine- just have to have the headset adapter....They
solved that with all the followup models.


"Michael Horowitz" > wrote in message
...
> Folks - I'm having difficulty getting audio from my Avcomm headset to
> my Icom A-21 handheld.
> The Icom requires a condenser microphone and the Avcomm has an
> 'electret' element, which as I understand is a variety of condenser
> mic.
> Has anyone had a similar problem and how was it solved? - Mike
>
> PS- I see a variety of circuitry on the 'net describing how to power
> the microphone, but I was hoping not to have to go off building
> another box.

[Michael Horowitz]

That my next step, but now it's a puzzle and I'd like to develop a
solution. Actually, the adapter I bought was not inexpensive and I'm
moping about being unable to use it. That's the real reason <G>
<sigh> you'rs is probably the best suggestion. - Mike

"RDA" > wrote:

>Everyone is trying to provide a technical solution. Kudos.
>
>Now just go out and buy (or try to find a used one, which is more like it)
>the HS61(? I think- mine's in the flite bag) headset adapter that Icom made
>for interfacing aircraft headsets with the A21. Works great, but that was
>the biggest problem with an otherwise good aviation band radio- all my Icom
>ham accessories work fine- just have to have the headset adapter....They
>solved that with all the followup models.
>
>
>"Michael Horowitz" > wrote in message
...
>> Folks - I'm having difficulty getting audio from my Avcomm headset to
>> my Icom A-21 handheld.
>> The Icom requires a condenser microphone and the Avcomm has an
>> 'electret' element, which as I understand is a variety of condenser
>> mic.
>> Has anyone had a similar problem and how was it solved? - Mike
>>
>> PS- I see a variety of circuitry on the 'net describing how to power
>> the microphone, but I was hoping not to have to go off building
>> another box.
>

[Michael Horowitz]

And at $178 can you blame a guy? - Mike

"RDA" > wrote:

>Everyone is trying to provide a technical solution. Kudos.
>
>Now just go out and buy (or try to find a used one, which is more like it)
>the HS61(? I think- mine's in the flite bag) headset adapter that Icom made
>for interfacing aircraft headsets with the A21. Works great, but that was
>the biggest problem with an otherwise good aviation band radio- all my Icom
>ham accessories work fine- just have to have the headset adapter....They
>solved that with all the followup models.
>
>
>"Michael Horowitz" > wrote in message
...
>> Folks - I'm having difficulty getting audio from my Avcomm headset to
>> my Icom A-21 handheld.
>> The Icom requires a condenser microphone and the Avcomm has an
>> 'electret' element, which as I understand is a variety of condenser
>> mic.
>> Has anyone had a similar problem and how was it solved? - Mike
>>
>> PS- I see a variety of circuitry on the 'net describing how to power
>> the microphone, but I was hoping not to have to go off building
>> another box.
>

[smithxpj]

On Fri, 26 Sep 2003 05:00:26 -0400, Michael Horowitz
> wrote:

>Folks - I'm having difficulty getting audio from my Avcomm headset to
>my Icom A-21 handheld.
>The Icom requires a condenser microphone and the Avcomm has an
>'electret' element, which as I understand is a variety of condenser
>mic.
>Has anyone had a similar problem and how was it solved? - Mike
>
>PS- I see a variety of circuitry on the 'net describing how to power
>the microphone, but I was hoping not to have to go off building
>another box.

The trap for players in this equation is that the electret (or
condenser) microphone in a standard GA headset is not connected
directly to the mic plug. The microphone input circuit on (standard)
aviation radios and intercoms (despite this day and age) is designed
to accommodate a CARBON capsule microphone by supplying a DC bias
voltage though a suitable input load resistance. Genuine carbon
microphones are rare these days but the electret (or dynamic)
microphone and a small transistor amplifier built inside the plastic
housing makes the whole assembly appear electrically as a
pseudo-carbon microphone to the GA radio.

The ICOM A-20 handheld , and I suspect the A-21, has an external
microphone input that accommodates a 'pure' electret microphone, and
*not* the pseudo-carbon of a GA headset. ICOM produced an outboard
adaptor for GA headsets to be used with the A-20 and the circuit was
custom designed to provide the correct DC bias for a pseudo-carbon GA
microphone and then to attenuate the high level voice signal down to
the much lower equivalent of what comes out of a 'pure' electret
capsule, which then goes into the ICOM microphone circuit. The adaptor
also had an amplifier to produce transmit sidetone

The other tricky part is the PTT. In GA this is easily accomplished by
grounding or earthing an independent PTT line which either engages a
relay or some form of solid state switching in the GA radio. In the
ICOM the PTT is activated by a DC voltage level shift when the
microphone is connected by a series PTT switch. The ICOM GA headset
adaptor achieves this with fixed value resistances that emulate the
same effect as switching in the 'pure' electret capsule.

The key to this whole exercise is getting the circuit for the innards
of the ICOM adaptor! The picture then becomes pretty clear.

I believe that later versions of the ICOM have worked around the need
for an 'electrical' adaptor with GA headsets by building the
microphone input circuit ready to accommodate pseudo-carbon in the
first place. Any outboard cables are now just 'plug size' and gender
changers rather than there being any amplifiers or matching circuitry.

A safe bet in this adapting and matching stuff is to always think of
the (standard) GA headset as having a CARBON microphone regardless of
what is written on the box. It's carbon as far as the electrics are
concerned, anyway!