Testing DVB cards to select which channel to use ...

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AndyInNYC
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Testing DVB cards to select which channel to use ...

Post by AndyInNYC » Tue May 23, 2017 5:00 pm

I'm running .28 MythTV on two Ubuntu 16 servers (master and slave). Both servers are configured 'mostly' alike and have a total of 3 ATSC capture cards - Fusion and Hauppauge and maybe a third.

Across the three cards, how can I check, individually, the reception of specific channels? Is there a way to tune or otherwise boost reception?

If I find that card 2 in machine 1 gets channel xx.1 and the others don't, do I just go into mythtv-setup and remove that channel from the other two cards list of channels the 'get'?


Thanks all.


Andrew

PhilB
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Re: Testing DVB cards to select which channel to use ...

Post by PhilB » Tue Jun 13, 2017 5:21 pm

Hi Andrew,
In the absence of more knowledgeable responses I’ll have a go at this
Across the three cards, how can I check, individually, the reception of specific channels? Is there a way to tune or otherwise boost reception?
I cannot say how to check reception, but my old Hauppauge tuners (T500) have a low noise amplifier which can be turned on/off. I have to do a cold boot for any change to take effect (even unrelated ones like changing from VGA to HDMI). External amplifiers are available but use these with caution – generally to make up for losses downstream from the amp.
If I find that card 2 in machine 1 gets channel xx.1 and the others don't, do I just go into mythtv-setup and remove that channel from the other two cards list of channels the 'get'?
Well the normal setup with 3 tuners is
a) if all three receive the same transmission then you would have configured: 3 tuners, one source, one channel scan. The scheduler would then choose channel from any available logical/real tuner.
b) If there are 3 different sources (eg DVB-T, DVB-S and cable) then you’d need to configure 3 tuners, 3 sources, 3 channel scans. The scheduler would choose any free (logical or real) tuner with a channel which matches the callsign set in the recording rule.

Now if you really wanted to hide or delete channels from particular tuners then you’d need to put each tuner in its own source. You can hide channels in the backend setup, in mythweb or in the perl based channel editor.
However, my gut feeling is that there is something more subtle going on than some tuners not picking up some stations and you’d be best served by trying to identify and eliminate that and adopt the simpler single source solution.

Your aerial and/or distribution setup or your local conditions (tidal waters, buildings in the way etc) may not be up to scratch. You may get some clues here (its UK biased but it's all about radio propagation which is universal):
https://www.mythtv.org/wiki/DVB-T_Reception_Problems

Alternatively, is it possible that you are picking up two transmitters – one strong local one and a distant and weaker (or off-axis) transmitter? That would give you ‘ghost’ channels with the same callsign which the scheduler might pick seemingly at random. The clue to these is the multiplex / freqid / frequency used by the channel. That can be ascertained from mythweb, the channel editor: https://www.mythtv.org/wiki/Channel_Editor
or from the API interface on your backend: https://www.mythtv.org/wiki/Channel_Ser ... elInfoList

If you do find rogues than you may need to do some web based research on frequency allocations in your area to identify what is going on and hence identify the transmitter.

Again you can hide the rogues in backend setup, in mythweb or the perl channel editor.

Hope you fix this frustrating problem.

Phil

wesnewell
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Re: Testing DVB cards to select which channel to use ...

Post by wesnewell » Wed Jun 14, 2017 6:54 pm

I've got my antenna connected to 6 tuners in my backend, 2 TV's, and an old VCR. I had to install a distribution amp to get good reception at all the tuners. Of course you also need a good antenna or source.Been working great for years.
Backend-GF8200A, AMD Phenom II 805, 6 atsc tuners. Frontends-GF8200's,,AMD Athlon II's,and boot drive.

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