For those of you who are trying to interface something to a rig
which has a single two-conductor plug for both microphone input
and push-to-talk connections, such as many of the handheld rigs
including the Icom IC-2AT and IC-02AT, here are three circuits
that may be useful to you:
::: Electret condenser microphone to radio:
Radio Shack #270-092 mic element?
MIC--------------+--------------------O------------> Mic/PTT on radio
| | |
| | | <-- Shield
+------///----+ |
| (20-30K) / <-- PTT |
| / switch |
+--------------------+ +-----------+------------> Ground on radio
::: Dynamic microphone to radio:
MIC +-----------------------O----------> Mic/PTT on radio
COIL C |
C |
C / | <-- Shield
| / |
+-----------+ +-------+----------> Ground on radio
::: High-level input (such as from tape recorder, RTTY AFSK generator,
or Packet TNC output) to radio:
HIGH LEVEL OUTPUT: RADIO INPUT:
(0.47 uf)
Audio to transmitter -------||-------+----O------> Mic/PTT on radio
(25K) | |
Push-to-talk -------///------------+ | <-- Shield
|
Ground -----------------------------------+------> Ground on radio
I made a big mistake in the previously-posted schematic of
the connection between an Icom IC-2A, 2AT, or 02AT and a
packet radio TNC, RTTY afsk unit, or another microphone.
The resistor and capacitor were backwards. The correct
schematic follows:
Audio
from TNC* PTT Ground
| | |
--- / |
(C1) --- (R1) |
| / |
| | |
Icom HT | | |
mic input------+-------------+ |
|
ground--------------------------------+
C1 - 0.47 uf capacitor
R1 - 25K resistor
* TNC or RTTY afsk or another microphone or whatever you are
interfacing to your Icom HT.
|
