[mythtv-users] mythfilldatabase

Stephen Worthington stephen_agent at jsw.gen.nz
Fri Mar 9 01:54:25 UTC 2018

On Thu, 08 Mar 2018 22:10:24 +0100, you wrote:

>I just had a curious behavior:
>For the first time since a long time, mythtv-setup began a scan and found 
>channels. But then suddenly the signal strenght was zero and then even after 
>excuting mythfilldatabase, in mythfrontend I cannot watch tv.
>I found the error message
>"DVBChan[1](/dev/dvb/adapter0/frontend0): Your frequency setting (2768000) is 
>out of range. (min/max:925000/2175000)"
>But I gave the frequency 10714000 khz that I found for Astra 19.2E (Gremany) 
>and that worked in the beginning for me. It seems that the setup first 
>accepted 10714000 khz (and worked) and then it jumped to 2768000 khz and there 
>was no more signal.
>Can anybody understand that ? I cannot.
>Nice evening

If I remember correctly how things work, the frequency in that message
will be the frequency sent to the tuner, not the frequency of the
multiplex you are trying to receive.  The tuners work with an
intermediate frequency produced by the LNB on your satellite dish. The
LNB frequency is subtracted from the real frequency of the multiplex
to get the frequency the tuner needs to tune to.  So for my satellite
(Optus D1 160.0E), if I want to tune to one of my multiplexes on
12456000 kHz, with my LNB frequency of 10750 MHz, then the tuner needs
to be set to the frequency of:

  12,456,000 kHz - 10,750,000 kHz = 1,706,000 kHz

The way LNBs work in Europe is that there are normally two LNBs on
different frequencies, to extend the range of frequencies that your
tuner is able to receive from.  If your satellite dish works like
that, then it looks like your LNB settings may only have the lower LNB
frequency in them, so when you try to tune to a multiplex on a
frequency that is too high to be received with the low frequency LNB,
the frequency calculated to receive from is too high for your tuner
hardware.  What should be happening is that the LNB settings have a
frequency setting above which the upper frequency LNB should be used.
So when you try to tune to a frequency above that setting, mythbackend
will send out a signal to the satellite dish to tell it to switch to
the upper frequency LNB and then will subtract the LNB frequency of
that LNB, and that will produce a frequency sent to the tuner card
that is within its frequency range.

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