Batboard

Hi all,
I have VERY low audio when using a GM300 and taking audio driectly from a Paccomm TNC. The GM300 works fine with a Kantronics KPC3!
And the Paccomm works great with a Kenwood.

Ultimately I want to interface the GM300 to a PC sound card for our APRS network.

Any suggestions to get past the +9VDC on the mic pin (electret mic?)?
Maybe that isn't the issue? I have tried moving the jumper at JU651.

Thanks
Dwight

Use a 10uF 16V electrolytic capacitor in series with the audio going to the GM300's MIC input, with the positive lead going towards the radio. You'll need a lot of signal, around 350 millivolts, which is a lot higher than what many Japanese radios require for transmit audio. Your PC sound card may or may not have enough level for this.

Bob M.

Thanks Bob,
I will hunt a 10µF cap down and try it.
The 0.1 non-polarized didn't help but I'll try it.

Thanks
Dwight