[mythtv-users] Digital switchover in UK: duplicate channels

Simon Hobson linux at thehobsons.co.uk
Wed Aug 17 14:16:41 UTC 2011

John Pilkington wrote:
>I retuned today as the last-but-one stage of switchover at Waltham, East
>Midlands.  All went smoothly but I wasn't able to stop it listing two
>different channel numbers for BBC FOUR, CBeebies, BBC Parliament and the
>BBC Radio channels.  It appears that at present these really are
>duplicates; they are available on two muxes.

This is common where you get a signal from more than one transmitter. 
There were a lot of complaints around (IIRC) the Chester area at 
switchover as they started getting Welsh variants of BBC2 and C4. In 
this case they were getting signals from two main transmitters, but 
it also happens if you get signals from the main transmitter and a 

In these cases, the system fills in channel numbers as it finds 
muxes. Up here (Winter Hill area) our main transmissions are from up 
the top end - so all the repeaters come further down. At a mates 
house, it picks up the barely usable (the aerial points the other 
way, so very low signal strength) local transmissions first and puts 
them in the main channel slots. Then when the unit finds the main 
muxes, it puts the "duplicate" channels up at 800+. For naff boxes 
with a dire excuse for a user interface, this sucks big time.
Fortunately for us, because of the way the muxes are laid out, I can 
unplug the aerial lead until the scan has passed the local 
transmissions, and avoid the problem.

In MythTV, I can see a number of ways round the problem.

1) Delete all channels and delete all transports.
Perform a tuned scan on one frequency at a time - there's only 6 
muxes to pick up.

2) As above, but experiment, and see if the option to find related 
transports will pick up just the muxes from the same transmitter. 
Then rescan existing transports.

3) Manually delete the transports you don't want, delete all channels 
and do a scan on existing transports.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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