Zgemma H7S oddities

[Knuckx]

I've just got a Zgemma H7S v2 from the forum sponsor, running OpenViX 6.3.007. I'm pretty happy with it, but I've got a few oddities to ask about:


I've got a Xbox One Digital TV Tuner plugged in to give me a second DVB-T/T2 tuner (using drivers-dvb-usb-dib0700). It works fine to watch TV, but the SNR/AGC/BER figures in the OSD and Signal Finder always show 0. I don't think I've set it up incorrectly - I'm guessing either the driver doesn't support these figures, or there's a driver bug. This issue does not affect any of the built-in tuners (on the built-in DVB-T tuner, I have SNRs between 50% and 90% depending on multiplex). Any ideas?
Relevant chunks of dmesg from a restart:

[   10.084476] dvb-usb: found a 'Microsoft Xbox One Digital TV Tuner' in warm state.
[   10.095573] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
[   10.108021] dvbdev: DVB: registering new adapter (Microsoft Xbox One Digital TV Tuner)
[   10.284535] mn88472 8-0018: Panasonic MN88472 successfully identified
[   10.301028] tda18250 8-0060: NXP TDA18250BHN/M successfully identified
[   10.313082] usb 1-1.2: DVB: registering adapter 1 frontend 0 (Panasonic MN88472)...
[   10.324564] dvb-usb: Microsoft Xbox One Digital TV Tuner successfully initialized and connected.
[   10.335194] usbcore: registered new interface driver dvb_usb_dib0700
...
[   27.651340] mn88472 8-0018: downloading firmware from file 'dvb-demod-mn88472-02.fw'
[   27.842015] platform dvb0.0: DVB: registering adapter 0 frontend 3 (vtuner)...

I have occasional EPG corruption (on the satellite EPG only, terrestrial EPG is unaffected) where all entries in the EPG become the same partial chunk of text from a random programme description. It seems to happen following an OpentvZapper automatic OpenTV download. I suspect that this is due to my old, rusting, badly aimed zone 1 dish that doesn't have the best signal strength. Is there any other reason this could be happening - or do I just put up with it until I get a nice new dish?


I'm using an expired white Sky card (CAID 0963) and softcams-oscam-latest to decrypt the few remaining FTV non FTA channels (basically London Live). It's working fine, but the card is showing no entitlements, even after leaving it to take EMMs continuously for 24 hours or so (no EMM types are blocked, and I can see them being written in the log). Does the lack of entitlements matter, since it's working to decrypt the FTV channels?

[abu baniaz]

The xbox tuner will not show signal values. Only image that will do so is openSpa.

Are you getting a lot of Bit Error Rare errors on your satellite services? A manual, single satellite scan should get more than 850 services.

[Knuckx]

The xbox tuner will not show signal values. Only image that will do so is openSpa.

OK, that's expected behavior then. No problem.

Are you getting a lot of Bit Error Rare errors on your satellite services? A manual, single satellite scan should get more than 850 services.

No, the BER is consistently 0. Certain combinations of transponders tuned simultaneously seem to cause picture blocking/garbage on one of the channels - for example NHK World HD (11225 V) and Channel 4 HD (12168 V) - though the BER shown in the OSD is 0 when this occurs. I get 863 services on a scan of 28.2E. I'm now suspecting my LNB is the problem and that the two halves of the LNB are interfering with each other, as the corrupted EPG has only occurred when I have been using the box when the OpenTV download has run.

[BrianG61UK]

OK, that's expected behavior then. No problem.


No, the BER is consistently 0. Certain combinations of transponders tuned simultaneously seem to cause picture blocking/garbage on one of the channels - for example NHK World HD (11225 V) and Channel 4 HD (12168 V) - though the BER shown in the OSD is 0 when this occurs. I get 863 services on a scan of 28.2E. I'm now suspecting my LNB is the problem and that the two halves of the LNB are interfering with each other, as the corrupted EPG has only occurred when I have been using the box when the OpenTV download has run.

I had the certain combinations of frequencies causing problems thing with my Zgemma H7S.

I assume that an oscillator (VFO) in one tuner leaks into the other tuner a bit and causes problems with weak signals on a certain frequency that depends on what the other tuner is tuned to.

I was able to fix it by using a pair of Labgear CM5220 satellite signal boosters and a pair of short cables with F connectors on the ends.
The CM5220 seems to have been discontinued, but there are other similar ones on eBay like:

https://www.ebay.co.uk/itm/153544214896 or
https://www.ebay.co.uk/itm/270468117287

Shorter or better quality cables from the LNB, or an LNB with a stronger output, might be alternative solutions.

[Knuckx]

I had the certain combinations of frequencies causing problems thing with my Zgemma H7S.

I assume that an oscillator (VFO) in one tuner leaks into the other tuner a bit and causes problems with weak signals on a certain frequency that depends on what the other tuner is tuned to.

Good to know I'm not the only person to have experienced this issue. Hopefully you are correct and this is only a "weak signals" problem.

Shorter or better quality cables from the LNB, or an LNB with a stronger output, might be alternative solutions.

A nicer LNB, and new, good quality cables is probably going to be my first choice of solution. I was planning on getting a new dish anyway, as my existing one looks like crap (it came with the house) and I would like to be able to receive from 19.2E and 13.0E. If that doesn't improve things, then I'll look at getting some amplifiers. Luckily the EPG corruption has only happened a few times, almost all of them when I was fiddling with the box.

[BrianG61UK]

Shorter or better quality cables from the LNB, or an LNB with a stronger output, might be alternative solutions.

Oh, and another possible, maybe, type solution I never looked in to would be to open up the Zgemma H7S and try and fix the problem with the design. Maybe a grounded metal shield fitted between the two tuners would do it. I chickened out of trying it myself though. Also, I hadn't fully formed my idea of what was probably going wrong until I found the booster solution worked well for me. I also have no idea whether my feeds from the dish are unusually weak or not.