UniTrunker and P25

[CrewRest]

What radios are being used to feed UniTrunker Motorola P25 system.

I can use UniTrunker on everything else but I can't get a P25 system to work. I've tried the OptoCom with it's built in discriminator, a BC-780xlt with a Discriminator Tap, and a BC-250d with a tap.

I have not tried an audio isolation transformer between the tap and the computer microphone input.

I'm running XP on a laptop with a SigmaTel sound board (built-in).

I must say the only P25 systems I've been able to try are the DOD systems in the 380-400 range. I've tried FM,WFM, and NFM.

Doug Anderson
KG4QCR

 

[SCPD]

Hi Doug;

I expected someone to reply by now. I have to use a buffer amp to isolate the disc. tap from the microphone or line input. For the BC780XLT - the difference is night and day.

-rick

 

[CrewRest]

Hi Rick,

I did too. I know others are using the OptoCom. It's a great little radio. This is the first time it hasn't been able to do something like this.

Do you think an isolation transformer (1:1) will work? Or does it have to be an isolation amp?

Doug

 

[SCPD]

I haven't tried using a transformer. If you can make an educated guess as to what the input impedance is on the microphone input. Line input should be 600 ohms. I'd suggest playing with a 10K to 600 ohm or 10k to 10k transformer. I suspect a 600 ohm to 600 ohm transformer would be too much of a load on the disc. tap in the radio. Considering how simple this is - I should have this ages ago.