[Icom] SM-20, HM12 and HM36

Mon, 23 Sep 2002 20:14:50 -0700

Hi Johnny,

All Icom electret mics, including the HM-12 and HM-36, are already fitted
with a built-in preamp which matches the electret output to the level
required by the transmitter speech amplifier. The SM-20 and SM-8 differ from
the hand mics in that they have a simple equaliser or tone control. Adding
any more gain to any of these mics would only overload the speech-amplifier
input.

One could add a "HIGH-LOW" tone control to the hand mic, but some "surgery"
would be required to install the "HIGH-LOW" switch. Is it really worth all
that effort?

Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/
Note new e-mail address:
mailto:[email protected]

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Siu Johnny
Sent: Monday, September 23, 2002 18:38
To: [email protected]
Subject: Re: [Icom] SM-20, HM12 and HM36

I am looking for a schematic diagram of SM-20.  Could you please advise
where I can download it.

SM-20 is a very good desktop mic as everybody knows.  One of the most
advantages is that there is an internal mic pre-amp.

I open up the HM12 and HM36.  I notice that the PCBs inside are less than
halfly filled with plenty of empty circuity.  I would like to know whether
it is possible to install a simple mic pre-amp inside these hand mics by
making use of the PCB inside.

I am looking forward to your advice.

73

Johnny Siu VR2XMC