Adding a PR781 microphone to a 6400

olson339

Hello

I am new hear and recently purchased a 6400. I have it setup and it is operational. Been able to make QSOs with the stock mic fhm-2. However I would like to start using my Heil PR781. I purchased an xlr to 3.5 trs cable. Connected the cable to mic and the mic port on the back of the 6400. Changed the mic type on SDR to the 781 profile however when I key (PTT) I am unable to see any activity/modulation from the 781on the rf panel. The 6400 goes into transmit. As I said the stock mic works perfectly. So I must be missing. Any help or suggestions would be appreciated
73
Art de N2AJO

AA1SS

You may need to turn on the 20db gain mic preamp. Also is it a 3.5 mono or stereo adapter??

olson339

Steve

20db is on and bias is off. 3.5 is stereo- TRS

Steve Ellington

I keep a little Radio Shack test amplifier handy for diagnosing stuff like this. Just feed the 781 into it to verify it actually works first. Once this is confirmed you need to ensure you are using the correct pins on the mic jack. I have used a 781 fed directly into the balanced mic. port., not the stock mic. jack. You then need to select the proper input in Ssdr. That would be BAL.

AA1SS

I purchased the Flex cable for that mic and it worked perfect. I originally purchased one off Amazon and it did not work for some reason. Never went further with it

AA1SS

I dont think the 6400 has a bal port just the one mic input. Only the 6600 has a balanced input according to the hardware manual

Steve Ellington

I keep a little Radio Shack test amplifier handy for diagnosing stuff like this. Just feed the 781 into it to verify it actually works first. Once this is confirmed you need to ensure you are using the correct pins on the mic jack. I have used a 781 fed directly into the balanced mic. port., not the stock mic. jack. You then need to select the proper input in Ssdr. That would be BAL.

AA1SS

The MIC connector accepts a 1/8-inch (3.5mm) stereo (TRS) plug and provides a pseudo-balanced microphone input. Pseudo-balanced means that the mic (+) and mic (-) lines are balanced all the way to the input of the A/D converter, where the mic (-) line is DC grounded. The connector may be used with dynamic or electret microphone elements. A software enabled 3V bias voltage through a 2.1k Ohm source impedance may be applied to the Mic (+) line for electret microphones.

Steve Ellington

Probably right. Mine is a 6600.

AA1SS

Tip is plus . . . Ring is minus on mic and sleeve is ground on the 3.5 mm plug

olson339

Yes decided to buy a cable from Flex. Will confirm once it gets here.