All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
R H Bevan: Digital UK's tradeview predicts that you should get the two multiplexes you do now, plus Mux A/SDN. Mux C/Arqiva A and Mux D/Arqiva B will stay on low power until after Tacolneston switches over in November, as their allocations clash with low-power services at that transmitter. Once the power is increased, the predictions are over 90% probability of reliable reception for all six multiplexes.
Note that it is possible to have too much signal as well as too little.
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Norman Smith: In OX25 you're likely to be using the Oxford transmitter. Mux 2, which carries those channels, is right at the top of the frequency range. Losing this often indicates that there is a problem with the cabling.
Has it been raining there today? Does it often coincide with wet weather? If so, it's likely that there's a leak somewhere allowing water to penetrate the dielectric of the cable - the insulation between the inner core and the outer screening - which reduces the ability of signals to travel along the cable. Higher frequencies suffer more loss than lower ones.
Check the seals on all external connectors and any boxes such as a masthead amplifier. The aerial should have been oriented so that the open side of the connection box, if any, faces down, so that any water that does get in can drain out. Also check that the cables are all well secured and haven't been rubbing against tiles or brickwork, as you start to get problems when the outer insulation wears through.
Finally, the outer insulation perishes with exposure to sunlight. They only last so long. If they've been up for more than 10 years they may need replacement.
If the dielectric is foam, it could be saturated and there's little that can be done to dry it out. If it's air-spaced, it should dry but water can run down it to the equipment at the bottom! There might be a loop where the cable enters the house, which could be full of water, which probably won't go away.
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Colin Tough: Durris commercial multiplexes now use the same frequencies as Knock More's public service multiplexes, and the Digital UK predictor shows that this co-channel interference is severe enough to stop you getting them from Durris.
The prediction for Knock More PSBs is actually slightly better than for Durris PSBs, and the Knock More COMs prediction is also good. You should be able to get a reliable six-multiplex service from Knock More.
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LF: If the aerial points to Craigkelly but it decides to tune into Black Hill, it probably indicates that the Craigkelly signals are too distorted to use. You should expect to get very high signal levels anyway - if you have any amplifiers or boosters, you should remove them. That might still leave you with too much signal, in which case you should add an attenuator.
Older boxes were often calibrated to the maximum possible signal from one multiplex - maximum safe levels (avoiding distortion) are often way below 100%. On my Humax box it's actually about 50%. I can't find a spec for the input range on your Pioneer box.
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Justin MacNeil: As far as we know, there are no faults on the transmitter. Can you provide a full postcode so we can see where you are?
It's common for viewers to have too much signal after switchover. If you have a booster, remove it. If reducing signal levels doesn't help, check with your neighbours to see if they can get HD signals, and if they can't either, use the BBC reception page at BBC - Reception problems .
As far as the first analogue channel to go is concerned, at main stations, the transmitter that is switched off/switched mode* is whichever the BBC A multiplex replaces, which was indeed C4. However, in cases where this is not BBC Two, the channel whose transmitter was switched off is moved to the BBC Two frequency for the two week changeover period.
That is, BBC Two closed down, C4 moved to C26, then BBC A started up on C29.
For West Linton it's likely that no change was actually required, because the same change (BBC A launching on C4's frequency, C4 moving to BBC Two's frequency) happened at the upstream transmitter, Penicuik. Faults at that transmitter, or the main transmitter, Craigkelly, would impact West Linton as well. Again, no problems have been reported.
* Largely the technical switch-over happened several months ago, and the old analogue transmitter or transposer was replaced by new dual-standard equipment, which is then switched over to digital operation on the actual switchover days.
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Wilf: Yes, it is encrypted. You need a Top-Up TV or BT Vision subscription to watch it.
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Percussim: Tennis took priority as two British women got through, as I understand it. Red Bee Media (who run playout for the BBC) don't always get the EPG data updated, or some boxes don't update if the programme ID doesn't change.
On other platforms, interactive streams don't even appear in the guide or provide now/next information. Me, I like being able to record the F1 Forum.
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Mark A.: Well, some advertising regions of Channel 5 are only available encrypted, but C5 don't do any regional programming. It just means you only get London advertising on Freesat or other free-to-air receivers.
I don't see why anything going free-to-view should require new cards. They should only issue new cards if the encryption scheme for the whole system is compromised, in which case you would lose access to all encrypted channels (free or subscription) if you didn't get a new card.
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Stewart Filshill: I'm not sure if all the boxes have a built-in RF modulator. If they do, you can just connect up an aerial-type cable from the box's RF output to the second TV. You just need the plain push-in 'Belling-Lee' connectors. I would recommend satellite-grade cable anyway.
You then tune the analogue tuner on the TV into the UHF channel configured on the V Box. You can only watch the channel selected on the V Box, so you would need a remote control extender as well.
If the box doesn't have a modulator built-in, you can buy an RF modulator that plugs into the box's SCART socket.
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Thursday 23 June 2011 4:24PM
Shuggy: In Glasgow, you would probably be using the Black Hill transmitter. All services were reshuffled to different frequencies on Wednesday morning (before 6am) as the analogue transmissions were turned off.
Everyone is recommended to do a full reset on both switchover days, and any subsequent major retunes involving frequency changes or mode changes, because some boxes will not discard previous channel information even if they detect new locations for those channels, or don't find the channels during one sweep.
If it's just a case of new channels starting up on an existing multiplex, the 'automatic scan' feature should work fine without discarding anything already known. You may still end up with channels that have closed in the EPG, and if a previous channel number is reused for a new service, or a channel moves to a different number, your box might not pick up the change or put the channel at the wrong place.