Connecting a Microphone to WriteLog
by Ric Plummer, KV1W (ric@kv1w.com)
Here is the general info on the work of hooking up audio here at KV1W. Hope it's
helpful.
This was applied to FT990, FT1000 & IC756 Radios. All using Heil Headsets.
1) The audio from the mic goes directly to the computer mic in. DO NOT ground its
shield to anything else.
2) The line out ( pick a channel, I used right for one radio ) goes to a Radio Shack
273-1374 600 ohm 1:1 isolation transformer. Across the secondary of that is a voltage
divider of 470 ohm and 100 ohm. The low end of the 100 ohm goes to the Mic Gnd. AGAIN, NO
CONNECTION TO ANY OTHER GROUND. The center of the divider goes to a 2K resistor and the
other end goes to Mic Input of the transceiver. The reason for the 2K is to mirror the
Heil mic. I have other audio mixing here, so 100 ohms is too low.
On the matter of grounds: Take this seriously or you get HUM !! By the way, the Heil
AD1-Y adapter for the Yeasu is WIRED WRONG. They use mic gnd for PTT gnd and as soon as
you plug in your PTT you get hum. Open up the 8 pin mic connector and redo this with
shield to mic gnd (pin 7) and black wire to the other ground (pin 5) and all is well. Heil
should know better ! The Icom adapter worked, so I didn't do any analysis.
That's it for Mic audio. Play a little with the levels on the computer contol panel to
equal that which you had with the mic alone, then set the wave level to be equal to that
when you play a recorded message.
The headphones is where it gets complicated. Your radio either has monitor to feed
transmitted audio to the headset or not. If it does, you can just plug in the headphones
and go. I added a DPDT relay to the phones so they either go to the radio or computer so I
can monitor recorded messages without keying the TX or I can listen to them as
transmitted. This gets to be too much without a drawing !!
I use the PTT output on the LPT port so that you are in TX before RF gets going down
the line. Only problem here is, don't plug it in until you start WriteLog or the computer
will key your transmitter.
Also in the box is the CW keying transistor from the LPT port as well as A/B control
for the two radio set up.
