No receive with Chinese MMDVM_HS HAT

MMDVM_HS Hat hardware
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W9DJE
Posts: 5
Joined: Tue Feb 05, 2019 1:26 am

No receive with Chinese MMDVM_HS HAT

Post by W9DJE » Fri Feb 08, 2019 5:00 am

Hello everyone. I posted in the Facebook group for Jumbospot & other boards but figured I'd try here also.

Bought a Chinese copy MMDVM board and I can't get it to receive. The sticker says to use offsets of +500 and +500. I set the offsets to those right away but no go on RX. Tried every offset from -10000 to +10000 in 100 increments. Nothing. I'm using my FT2DR set for half deviation and narrow digital voice. I tried wide voice for a bit and no go. I set Pi-Star to YSF only and tried every parrot and nothing ever shows up on the dashboard for local RF. I originally started with 3.4.17 but figured I'd try 4.0RC3... No difference. I also didn't back up my config when I wiped the card, figuring I'd go through the entering of info all over again just in case.

I even transmitted on every .005 increment from about 1.5 MHz below to 1.5MHz above with the FT2DR (with the RX offset at 0) just to see if I could get the thing to receive something and no go.

I tried 446.250 for a while, then 433.800, then 438.800. No change.

I updated the firmware to 1.4.14. It originally was 1.3 something. No difference.

I tried RXInvert at 1 for a bit, but that made no difference. I have to try it with it at 1 and go from -10000 to +10000 yet, but I don't have much hope of that helping. Has anyone needed to use RXInvert with YSF?

Through all this, transmit works perfectly on YSF and DMR. I can listen in on YSF with the FT2DR and I can listen in to DMR with a scanner. IDs come accross on the FT2 and the audio is good.

I even tried 2M as this board is capable (according to the eBay ad) but it transmitted way low (Set it at 146.540 and it was on 137.330!) and I couldn't copy any of it.

If any of the solder joints on the TCXO are bad, would that cause it to be deaf? Sucks because I can't check them right now, due to the OLED display being in the way. I'm not desoldering the display unless I think that's a great possibility...

Need some help as this is now above my knowledge level. Any other ideas besides trying RXInvert from -10000 to +10000? Should I go even farther? The highest or lowest offsets I've read on my searches were that so that's why I stopped there.

M1DNS
Posts: 406
Joined: Thu Apr 05, 2018 5:30 am

Re: No receive with Chinese MMDVM_HS HAT

Post by M1DNS » Fri Feb 08, 2019 8:22 pm

Many of the Chinese adds on eBay haven't actually got a clue what they are referencing. If you look almost every one suggests an offset of 500 but the offset will differ slightly from radio to radio and the very reason ur tuning for best performance.

Either use pistar-mmdvmcal or continue manually in the hope that you can tune and find the sweetspot by making gradual adjustments to the offset settings.

Additionally many state they work at 2m when in effect they don't. but agn it's just the Chinese cloning regime making $$$ with supply and demand.

Finally to offer balance and stop many of the jumbospot and Chinese clone users jumping all over the post, there are some that do work and do what's required... I'm simply saying there's many more that aren't what they state they are. :-)

Andrew M1DNS, (Mod)

Andrew M1DNS.
Pi-star Admin Team.

W9DJE
Posts: 5
Joined: Tue Feb 05, 2019 1:26 am

Re: No receive with Chinese MMDVM_HS HAT

Post by W9DJE » Fri Feb 08, 2019 10:30 pm


M1DNS wrote: Either use pistar-mmdvmcal or continue manually in the hope that you can tune and find the sweetspot by making gradual adjustments to the offset settings.
I actually tried mmdvmcal for a bit and verified that it transmits the DMR test tone just fine, but the only thing I saw it could do for receive was an RSSI reading. (That and BER.... If it actually received something that could be useful!) Unfortunately, when I enabled that it just kept giving me a random low reading. (Like -90 ~ -100dbm.)

Any idea how far is far enough up & down for the offset? Is there a limit?

And have you ever seen anyone use the RXInvert?

M1DNS
Posts: 406
Joined: Thu Apr 05, 2018 5:30 am

Re: No receive with Chinese MMDVM_HS HAT

Post by M1DNS » Fri Feb 08, 2019 10:38 pm

As pistar uses a ' template' for each device in the modem configuration drop down the settings on Tx / Rx invert etc. should be set correct, but I guess no harm in trying it. There's a good pistar-mmdvmcal how-to in the PS FB group by Vic, I'll try to link it here, but need to find it first.

Andrew M1DNS, (Mod)

Andrew M1DNS.
Pi-star Admin Team.

W9DJE
Posts: 5
Joined: Tue Feb 05, 2019 1:26 am

Re: No receive with Chinese MMDVM_HS HAT

Post by W9DJE » Sat Feb 09, 2019 3:18 am

Success!

But it's weird...

So I was playing around with it today and simply clicking on stuff to either stumble upon something or permanently break it once and for all and...

I clicked on "Duplex" and tried it. As you'd expect... No difference. It is a simplex board so that shouldn't work. But when I clicked it back to "Simplex Node" BAM the receiver came alive! I played around with offsets and tested for about an hour and I can get the BER down to around 1.0% or so OR I can get good decode when I turn on Wires-X and browse for nodes on the radio. I definitely have to find a happy medium so much more testing is needed but it is receiving and I'm getting great audio back out of the parrots I tried.

Don't ask me why. I can't explain.

G4AON
Posts: 57
Joined: Tue Apr 24, 2018 5:34 pm

Re: No receive with Chinese MMDVM_HS HAT

Post by G4AON » Tue Feb 12, 2019 12:10 pm


There is a web page on calibration here:
http://www.k9npx.com/2019/02/hotspot-of ... n.html?m=1

73 Dave
ID51E plus 2
ID5100E
TYT MD-UV380
Chinese MMDVM on a Pi Zero W
DVAP on a Pi 3B
Shark OpenSPOT 2

W9DJE
Posts: 5
Joined: Tue Feb 05, 2019 1:26 am

Re: No receive with Chinese MMDVM_HS HAT

Post by W9DJE » Wed Feb 13, 2019 1:04 am

Thanks! I may try that with the YSF BER test in MMDVMCal. I was able to get my BER down to under 0.5% and yet the hotspot responds to WIRES-X commands almost 100% of the time so I'm pretty happy.

I just wish I understood why I needed to "jumpstart" the receiver the way I did. Really weird but I'm happy as it's working now.

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