[mythtv-users] multiple transmitters - same channel

Mike Perkins mikep at randomtraveller.org.uk
Wed Mar 19 12:45:42 UTC 2014

On 19/03/14 03:08, my thtv wrote:
> I have been using Mythtv for some years, however, recently here in Sydney
> Australia they have been retuning the digital (DVB) transmit frequencies.So I
> took the opportunity to re-scan my channels.However, I am in range of a number a
> transmitters and in some instances they are carrying the same services but
> signal strength and quality varies between them.
> I allocated different channels for the different transmitters in order to
> compare the quality of my reception from each source.However, I believe myth is
> not tuning to each but defaulting to a particular transmitter, regardless of the
> channel selected.
> So I had a look at some of the tables in mythconverg to try to determine why
> that may be.When checking channelscan_channel and channelscan_dtv_multiplex it
> appears that the latest scan correctly identify the same channel information
> with multiple entries for each frequency.I also checked dtv_multiplex, however,
> this table did not have all the available frequencies listed.It would seem that
> where transportid and networkid are identical for two different frequencies then
> only one of the frequencies is shown.
> So my questions are;
> Can mythtv show the same channel (2 channels with identical transportid,
> networkid and serviceid)but on different frequencies?
> If not how can you choose which transmitter between multiples transmitting the
> same channels?
This is the same problem I face in the UK. The way I resolve it here is:

1. Check online to find out what frequencies your preferred transmitter is using.

2. Do a scan-all and see if any of those frequencies are picked up. In 
'Transport Editor' keep one and delete the rest.

2a. If your preferred transmitter isn't picked up (unlikely since it will be the 
strongest signal) you'll have to edit one of the other entries and try with that.

3. In Channel Editor, delete every channel found. This will prevent 'ghost' 
channels causing confusion later. (I have been known to do this using mysqladmin 
but don't tell the devs.)

4. Do a 'Scan specific Transport' selecting the frequency you picked up, ticking 
the box for using associated frequencies (I forget the wording).

5. Profit!!

-> Another option you might consider is to visit your friendly aerial installer 
and see if he has any band-pass filters. That could make your problem less severe.


Mike Perkins

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