[mythtv-users] multiple transmitters - same channel

John Pilkington J.Pilk at tesco.net
Wed Mar 19 13:07:11 UTC 2014

On 19/03/14 12:45, Mike Perkins wrote:
> 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.)

Isn't this a single-box tick in the Channel Editor?  Agreed that it's 
required, or at least a Good Idea.

Note that tick/check is a prime example of UK/USA being 'divided by a 
common language.'   Don't know about Oz.
> 4. Do a 'Scan specific Transport' selecting the frequency you picked up,
> ticking the box for using associated frequencies (I forget the wording).

And the success of that will depend on correct transmitter-specific data 
being inserted at source.  Mostly works for me in the UK.
> 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.

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