MMDVM hotspot -- DR-2X repeater bridge
Posted: Sat Apr 09, 2022 7:00 pm
I've searched this topic and can't find anything. If it has been discussed and I missed it, then I apologize.
We have two DR-2X repeaters running AMS/AMS. We want to bridge the 2-meter repeater to our FCS 00388 node using an MMDVM hotspot. The hotspot is running separate TX/RX frequencies using the appropriate repeater uplink/downlink frequencies. Testing with HTs has been perfect. However, there is a problem.
When the hotspot is next to the repeater, the repeater receives the hotspot's transmission, but it "thinks" it's FM, not C4FM. When set in AMS/AMS, the repeater won't transmit what it receives. When it set in AMS/Fixed Digital, it will transmit what it received, but it's just digital hash.
We have looked at the hotspot output with a station monitor and compared it to the output from two different Yaesu HT's (FT5 & FT70). It is markedly different. Both HT's transmit a very short sine wave, then the digital wave can be seen superimposed on the sine wave. However, the hotspot transmits a much longer sine wave before the digital wave is seen. It's clear that the longer sine wave is what is making the DR-2X repeater think it is receiving analog FM instead of C4FM. We have tried making numerous changes to the pi-star configuration, but nothing has fixed the problem.
The problem is clearly with the MMDVM/Pi-star combination, because an OpenSpot2 works perfectly in this application. The repeater receives the OpenSpot2 signal and transmits it in C4FM.
Has anyone dealt with this problem? Three guys with a lot of test equipment are out of ideas. We know the cause of the problem, but not a fix.
Thanks,
Chas.
We have two DR-2X repeaters running AMS/AMS. We want to bridge the 2-meter repeater to our FCS 00388 node using an MMDVM hotspot. The hotspot is running separate TX/RX frequencies using the appropriate repeater uplink/downlink frequencies. Testing with HTs has been perfect. However, there is a problem.
When the hotspot is next to the repeater, the repeater receives the hotspot's transmission, but it "thinks" it's FM, not C4FM. When set in AMS/AMS, the repeater won't transmit what it receives. When it set in AMS/Fixed Digital, it will transmit what it received, but it's just digital hash.
We have looked at the hotspot output with a station monitor and compared it to the output from two different Yaesu HT's (FT5 & FT70). It is markedly different. Both HT's transmit a very short sine wave, then the digital wave can be seen superimposed on the sine wave. However, the hotspot transmits a much longer sine wave before the digital wave is seen. It's clear that the longer sine wave is what is making the DR-2X repeater think it is receiving analog FM instead of C4FM. We have tried making numerous changes to the pi-star configuration, but nothing has fixed the problem.
The problem is clearly with the MMDVM/Pi-star combination, because an OpenSpot2 works perfectly in this application. The repeater receives the OpenSpot2 signal and transmits it in C4FM.
Has anyone dealt with this problem? Three guys with a lot of test equipment are out of ideas. We know the cause of the problem, but not a fix.
Thanks,
Chas.