All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Graham: The Tacolneston retune affected Mux B and C, which moved to new frequencies - C66 and C68 respectively. BBC Four, CBeebies and the radio channels are on Mux B. Check whether you have any equipment, such as a Sky box or VCR, that outputs on C66, C67 or C68, and if so, retune it to another location.
You do need to do a 'first time installation'/default setting/full retune when these retunes occur, because some receivers will not store channels that they think they already know about.
There is a possibility that your box might store channels from Sudbury/Rouncefall if you do a full retune - Digital UK's postcode checker (trade view) shows that they should be strong enough for reliable reception if the aerial is pointed in that direction, which means it could store them even though the aerial points in a different direction. If you find that the BBC channels have all become unreliable after you do a full retune, see Digital Region Overlap.
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m Wainwright: If you have two different transmitter IDs showing up, it's likely that you have a case of Digital Region Overlap. A couple of threads on avforums.com suggest that transmitter ID 3064 is Sutton Coldfield while 3084 is The Wrekin, though the 'name' is set to West Midlands for both. Malvern might be using the same multiplex data as Sutton Coldfield, though.
In the screen that's showing the transmitter IDs, can you check that the UHF channels/frequencies it's tuned into match those that Malvern transmits on? To calculate the frequency for a channel number, subtract 21 from the channel number, multiply by 8000 kHz, and add 474000 kHz. If there is a + after the channel number, add 167 kHz and if a -, subtract 167 kHz.
If the frequencies indicate that other transmitters are being used, try clearing all channels and doing a manual retune on the frequencies used by Malvern. If that produces worse results than what you have now, or it won't tune in at all, the communal system engineer will need to figure out why.
If this is a channelized system - where each channel desired is filtered and amplified separately, all undesired channels being unamplified or even dropped - it will need to be retuned at switchover. Make sure that the engineer is using the *current* list of channel numbers (middle row above) rather than the after DSO list (bottom row): unusually, Malvern will use *none* of the current channels, either analogue or digital, after DSO. (The local service on C51 won't start until at least 2013.).
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john lowe: It's probably a case of too much signal for the PSB multiplex channels on C53 (ITV1, ITV1+1, ITV2, C4, C4+1, More 4, E4, Channel 5). You are only about 1km from the Budleigh Salterton relay, which uses the same channels as Beacon Hill, in a Single Frequency Network. However, it only relays the PSB multiplexes.
For the COM multiplexes (ITV3 is on SDN, ITV4 on ArqB), it looks like a number of other relays in the area use channels 42, 45 and 51. You may just be out of reliable reception range. Digital UK offers no prediction on these three multiplexes.
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john lowe: Sorry, I explained the problem, I didn't provide a solution. Since this is a distribution system, you need to arrange with the landlord - unless you are the landlord of course! - to get it looked at. Either the signal at the distribution amplifier is too loud - causing the amplifier to distort - or the signal coming out of it is too loud, causing distortion in your TV or box.
You could try adding an attenuator between the box and the wall socket, to reduce the level before it reaches your box, but as I say, the problem could be before the distribution amplifier.
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Kevin Mitchelson: If you just had a new aerial fitted, why are you asking us and not whoever erected it for you?
The most likely explanation at that postcode is too much signal - get the installer to fit a smaller aerial!
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Robert: It really sounds like you need some expert help. Try a CAI-registered installer who specializes in SMATV systems. You can search at Directory Search Page .
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kipsonline: The Waltham transmitter started switchover last Wednesday and no longer transmits BBC Two analogue. ITV1 analogue has temporarily moved to BBC Two's old location until the 31st, when it, along with C4 and C5 analogue, will shut down permanently.
To diagnose properly we need a full postcode. I can only give general advice.
Very old equipment - before about 2004 - may not support 8K mode, or may not support it properly. This mode was always in the DVB-T spec, and it has some advantages; most other countries never used 2K mode. A partial list of equipment known to have problems with it is at http://www.digitaluk.co.u…ment .
Also, some older equipment cannot handle a large Network Information Table, that doesn't fit into one block - it's said to be 'split'. The NIT got too big in 2008, but many boxes don't have a problem until they're retuned. Again, see http://www.digitaluk.co.u…tnit .
There's a large overlap in coverage between the Belmont transmitter in east Lincolnshire and Waltham. A lot of boxes will store the first version of the channels they find, when scanning from lowest frequencies to highest. Belmont is on much lower frequencies than Waltham. You might find the Waltham channels in the 800 range. If so, see Digital Region Overlap for ideas on fixing this.
If you're sure it's tuning into the correct channels, and you still have problems, see Single Frequency Interference, although you would have seen interference on ITV1 analogue before switchover.
If you're fairly close to the transmitter - and it looks like you're close enough - it could be a case of too much signal. If you have a booster or other amplifier, remove it or turn it down. If that doesn't help, try adding an attenuator.
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David Corrick: Looking at your location I'd suspect too much signal rather than too little. If you have a booster or other amplifier, try turning it down or removing it. You might try adding an attenuator to reduce signal levels.
You won't get C47 unless your TV or box has the Freeview HD logo. This multiplex transmits with a newer standard, called DVB-T2, which gives much more capacity. If your TV is 'HD Ready', you can add a Freeview HD set-top box or PVR to decode the HD signals.
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Iain Nicol: Probably both of those, and the polar response of the aerial as well. See Aerial Polar Reponse Diagrams for an explanation of polar response and some examples.
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Thursday 25 August 2011 1:31PM
tim harrison: For Waltham, *East* Midlands news, you need to tune into C61, 794 MHz, not C41. C41 is Sutton Coldfield.
There is a large overlap between Belmont (the Look North service) and Waltham. Older boxes and TVs were often not designed to handle receiving signals from more than one transmitter, and they often store the first version found at the advertised channel numbers, rather than the best quality version (which should be the one your aerial is pointing at).