RX Issue; RX/TX swapped on 1.0 board?

[hb9eue]

Hi

This is not a bug report, more of a question...

I have a 1.0 board, which basically works fine, but performs very badly, especially RX.TX/RX are 7.6 Mhz apart as usual in Europe on the 70cm band. So I feared the RX filters are not good enough and the RX is being swamped by the TX of the very close TX antenna in DMR mode.

From the pictures of newer revision boards, I know the bottom antenna is labeled TX. So I connected a propper antenna, placed outside of the building on the upper SMA connector, to have the RX antenna outside of the building and away from potential QRM.

To my surprise, the reception was even worse. Already about 500m away from the hotspot, I can not open the repeater, even with a hytera mobile set to HIGH power.

To compare, a dvmega based board receives fine from about 2km away.

So back to analyze the situation. I noticed, the Dual Hat does not even start to send, so it does not receive anything. So it cannot be a filter problem.

So I attached a 50Ohm dummy load to the bottom SMA connector and measured the voltage with an oscilloscope across it to verify the output power. None! The bottom SMA connector is NOT outputting anything.
Swapped around. Yes, on my 1.0 board, running firmware 1.4.14 the UPPER SMA connector is the TX one. I measure 0db so 1mW, which sounds about right.

So i also swapped antennas and put the outdoor antenna to the correct RX SMA socket.

The HS_Dual_Hat still is deaf!

Is this a know issue? Are the coupling capacitors on the RX path known to fail or similar?

Is it recommended to throw the 1.0 board in a bin and get a new 1.3 one?

-Benoît- / HB9EUE

[phl0]

That sounds very strange to me. AFAIK RX and TX didn't change over the revisions. I will check that. What is the result if y oiu run it in simplex mode?

[kitesurfer1404]

I had a similar issue until some minutes ago. No RX at all. TX worked great for staticly forwarded TGs from Brandmeister. By "accident" I found this tutorial
http://mmdvm.bi7jta.org/2018/04/userguide-for-duplexhotspot-only-for.html
and the comment down below asking why you have to choose "STM32/DVM_MMDVM_HS" as modem instead of "MMDVM_HS_DUALHAT".

I tried. Changed the modem to STM... in pi-star. Not it works for me.

Maybe this helps. An explanation would be nice. I want to believe understand. ;-)