<br><br><div><span class="gmail_quote">On 26/03/2008, <b class="gmail_sendername">Mike Perkins</b> <<a href="mailto:mikep@randomtraveller.org.uk">mikep@randomtraveller.org.uk</a>> wrote:</span><blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex">
James Cummings wrote:<br> > On Tue, Mar 25, 2008 at 11:05 PM, Tim Sawyer <<a href="mailto:mythtv@calidris.co.uk">mythtv@calidris.co.uk</a>> wrote:<br> >> I haven't done a channel scan for ages, yet this problem has been intermittent<br>
>> for ages, seemingly on only one of the two tuners.<br> ><br> > Given that your address is in the UK (where I am as well), I would<br> > strongly recommend doing a rescan of existing transports on a regular<br>
> basis. The small variations in channel line-ups and frequencies<br> > *always* cause problems on my box (with a Nova-T 500). It will be<br> > recording fine for awhile, then suddenly not be able to find files for<br>
> programs it believes it has recorded. A rescan of existing transports<br> > always seems to solve this. Whenever another freeview STB of mine<br> > announces that "There has been a change in channel line-up" (even if<br>
> it doesn't turn out to be a visible), I always go into the lounge and<br> > rescan the mythtv box. This seems to happen every few weeks. This<br> > seems to solve the problem. Perhaps it isn't the rescan of existing<br>
> transports, but the stopping and restarting of the backend that one<br> > has to do to run the setup... but that is what seems to work for me.<br> ><br> > I'm going to be upgrading the box from Ubuntu feisty to gutsy soon<br>
> (in preparation to eventually upgrade to Hardy in a couple months or<br> > so)... I hope that doesn't mess things up too much.<br> ><br> <br>You can get some indication of channel changes by checking the backend log(s) on<br>
an occasional basis. I can't remember the exact message to look for, but if your<br> logs suddenly start growing rapidly (you do use logrotate, don't you?) then it's<br> worth a check, and then a rescan if necessary.<br>
<br> Another fun thing to watch out for is if your aerial is able to pick up from<br> more than one transmitter. As the transmitters (people) are in the process of<br> changing the transmitter (equipment) power levels you may find that channels<br>
which were in one multiplex suddenly move to another one and thus disappear from<br> your lineup.</blockquote><div><br class="webkit-block-placeholder"></div><div><br class="webkit-block-placeholder"></div><div>Well, this is what caused me some problems just recently. I'd upgraded last week from Ubuntu 6.10 to 7.10 and with it to MythTV 0.21. I ran mythtv-setup and deleted my tuners as recommended and then did a rescan of channels,</div>
<div>in the past before the upgrade this has seemed to work ok.</div><div><br class="webkit-block-placeholder"></div><div>However I noticed that the quality of picture after the scan seemed much worse than with ubuntu 6.10 and mythtv 0.20.2?</div>
<div>There were many more pops/squeeks and digital signal drop outs than before, I had not physically moved the PC</div><div>whilst doing the upgrade (combined be/fe) but I started checking all the connections to the aerial, even re-made some of them. Checked the pre-amp etc etc. Still no improvement.</div>
<div><br class="webkit-block-placeholder"></div><div>I'd kind of given up on it and then yesterday morning I put it on just to see if anything had improved and was greeted with a 'no signal' message across all channels! I rebooted just in case and it was the same, I switched the TV off in disgust.</div>
<div><br class="webkit-block-placeholder"></div><div>Later that day I heard that our local TV transmitter, which is about 7 miles away was off air for maintenance, *all day*.</div><div>It did not concern me as I was pointing at a more distant transmitter which in my location (surrounded by taller buildings in some directions) gives a better signal. Then the penny dropped. Could it be that my MythTV box was tuned in to the wrong transmitter all this time and when I checked it this morning and there was no signal, that was the local transmitter off air!?</div>
<div><br class="webkit-block-placeholder"></div><div>I confirmed with some family that the local transmitter was still off and decided now was an ideal opportunity to do a re-scan for channels! I did this and what do you know, the signal quality is much better and just like it used to be.</div>
<div><br class="webkit-block-placeholder"></div><div>As I am in the UK too, I will be checking the websites below and making sure this does not happen again.</div><div><br class="webkit-block-placeholder"></div><div>Mike</div>
<div><br> </div><div><br class="webkit-block-placeholder"></div><br><blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"> This link gives you the exact frequencies for each UK TV channel:<br>
<a href="http://www.digitalspy.co.uk/terrestrial/tuning/">http://www.digitalspy.co.uk/terrestrial/tuning/</a><br> note that the DVB multiplexes use centre frequencies; the ones given above (I<br> believe) are the lowest frequency in each channel band. Then use this link:<br>
<a href="http://www.dtg.org.uk/retailer/transmitters.html">http://www.dtg.org.uk/retailer/transmitters.html</a><br> to find out which transmitters near you use which channels to send which<br> multiplex. Use the Transport Editor screen in mythtv-setup to find out which<br>
multiplexes the full scan picked up, and work out which transmitters sent which.<br> Delete ('D' key) the ones you don't want, then 'Rescan existing transports' to<br> give you a clean channel line-up. This Link:<br>
<a href="http://www.dtg.org.uk/retailer/dtt_channels.html">http://www.dtg.org.uk/retailer/dtt_channels.html</a><br> will tell you what digital channels are carried by which multiplex. * This list<br> is the one which can (and does) change from month to month.<br>
<br> Incidentally, I use three K-World DVB-T 100 cards (£30 each from Maplin) to get<br> my digital input, and have found no difference between the cards. They do take<br> 25-30 watts *each* power, so should only be used in a well-ventilated back end.<br>
<br> Hope this helps.<br> <br><br> Mike Perkins<br> <br><br> _______________________________________________<br> mythtv-users mailing list<br> <a href="mailto:mythtv-users@mythtv.org">mythtv-users@mythtv.org</a><br> <a href="http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users">http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users</a><br>
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