MTR-2000 Base Station (Simplex) & Pi-Star

Radio Equipment that can be used in Amateur Radio and where to get them. User support for those little problems that frequently occur and other little issues relation to Radio Equipment
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VA3UV
Posts: 47
Joined: Tue Apr 09, 2019 5:02 pm

MTR-2000 Base Station (Simplex) & Pi-Star

Post by VA3UV »

Hi Guys:

Got an MTR-2000 VHF "beast" for a simplex module on my repeater stack - it's setup as a
base station with a TX/RX relay.

I have an issue that I haven't had much time to investigate... I have it
connected to a DVRPTR modem and Pi-Star. Pi-Star is set for simplex
mode. The issue is that when Pi-Star sends the ACK beep, the MTR gets
into a loop chasing itself, keying the TX on and off. This happens on a
dummy load as well!

I thought maybe it might be programmed as a repeater
/ full duplex - BUT - if I disable the ACK in Pi-Star (Set the Mode value in dstarrepeater to 2), the MTR is fine -
whether with local RF traffic or traffic off a reflector, the thing
behaves perfectly, no tail chasing.... I think this confirms that it is
programmed correctly for base station / simplex use?

I tried playing with the txdelay and ACK timing in dstarrepeater - but even with timing values > 500, the problem persists. I'm wondering if the Mode parameter is not being 'respected' when dstarrepeater sends the ACK?

I have the Motorola RSS s/w - just need a darn XP machine to load it on and check
this out.

Any ideas.... anyone have an MTR-2000 and Pi-Star to validate my observation?

Thanks!

Ramesh.
VA3UV / WA3UV / G4PNQ
VA3UV
Posts: 47
Joined: Tue Apr 09, 2019 5:02 pm

Re: MTR-2000 Base Station (Simplex) & Pi-Star

Post by VA3UV »

I think the application here is actually 'Half Duplex' and what I really need is an RXDELAY rather than a TXDELAY.

Does dstarrepeater support such an application?

Thx,

Ramesh.
VA3UV / WA3UV / G4PNQ
VA3UV
Posts: 47
Joined: Tue Apr 09, 2019 5:02 pm

Re: MTR-2000 Base Station (Simplex) & Pi-Star

Post by VA3UV »

Hi Folks:

two years on and I am experiencing the same issue with Pi-Star and the MTR2000 (used as a base station, not a repeater).

Pi-Star v4.1.6

In Pi-Star, I have the mode set as simplex.

I am using a STM-32 Black (v4) Pi-Hat Board.

What I am experiencing is:

Local RF traffic (any mode) - seems to work fine; Pi-Star shows the local RF user on the dashboard (under local RF activity). In D-Star, I get the Ack back, all seems to be normal. However, when I hear traffic off the network (reflector, etc.) it is causing Pi-Star / the MMDVM board to chase itself at the end, meaning a continual PTT / drop / PTT, etc.

Last night, I disabled D-STAR mode, and set Pi-Star to DMR mode only. Again, local RF traffic seems to be fine. The issue, somewhat similar to the above, is that traffic off the Net, is appearing as BOTH Network traffic AND RF traffic. Even when there is traffic off the Net, the Pi-Star dashboard (on the left side under radio info) shows that it is receiving DMR traffic (rather than transmitting DMR).

In Simplex mode, I would have expected the system to be doing one thing - either transmitting - or - receiving. It appears that there is some kind of duplex loopback going on.

However, I have used this very same MTR2000 with a DVRPTR v1 board successfully over the past 2 years (how time flies!). As you can see from my original post, I did have a similar issue (in D-STAR mode only, since the DVRPTR board is limited to D-STAR... but heck, I wish I had made a note of the solution, or replied to my own note!).

Thinking this may be the MTR2000, I have deliberately increased the TX/RX antenna relay switching time to around 650mS (it was 125mS).

I should point out that on this Pi, I have ircddbgateway disabled, since for D-STAR, I am using this as a second RF module with another Pi-Star (which worked fine for the last 2 years).

Open to suggestions... anyone seen this before?

Thanks!

Ramesh.

VA3UV / WA3UV / G4PNQ
VA3UV
Posts: 47
Joined: Tue Apr 09, 2019 5:02 pm

Re: MTR-2000 Base Station (Simplex) & Pi-Star

Post by VA3UV »

After some further probing with the scope this weekend... the MTR2000 is actually operating in full duplex mode. The Base Station config just means that there's no repeat function.

There is some cross-talk between the TX and RX audio path, which is causing the MMDVM board to decode the audio signal in the RX audio chain.

Since Pi-Star is set for simplex (or half-duplex) operation, I would have expected it to ignore anything on the RX audio line, when the MMDVM is transmitting.

Is there such a configuration? (I think I have tried all of them.. but may be not!)

Thanks,

Ramesh.

VA3UV / WA3UV / G4PNQ
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