BBC4 HD - tuner says strong signal, TV says weak signal
Can anybody make sense of this conundrum?
I have a choice of either Belmont or Waltham. Manual tuning on Belmont Channel 28 shows signal 68%, quality 100%. Manual tuning on Waltham shows signal 77%, quality 100%. (perhaps 28 and 58 are multiplexes rather than channels - damned if I know).
So why can't I suddenly not pick up BBC4 HD do to a weak signal? I've tried a manual search on both, each time storing all the channels found, yet I'm still getting a constantly broken or non-existent signal. It probably effects a few minor channels as well, but I haven't bothered trying them all.
I have a choice of either Belmont or Waltham. Manual tuning on Belmont Channel 28 shows signal 68%, quality 100%. Manual tuning on Waltham shows signal 77%, quality 100%. (perhaps 28 and 58 are multiplexes rather than channels - damned if I know).
So why can't I suddenly not pick up BBC4 HD do to a weak signal? I've tried a manual search on both, each time storing all the channels found, yet I'm still getting a constantly broken or non-existent signal. It probably effects a few minor channels as well, but I haven't bothered trying them all.
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http://tx.mb21.co.uk/gallery/gallerypage.php?txid=807
And UHF 26 on Waltham
http://tx.mb21.co.uk/gallery/gallerypage.php?txid=679
And is transmitted at lower power ....
http://www.digitaluk.co.uk/coveragechecker/main/trade/LN5+7EJ/NA/0/4d2tm4h75b8op9emqnjuq4ufu5 is a prediction for the Lincoln Co-Op. Hover over the transmitter frequency numbers to get the power transmitted for each transmitter mux in turn.
Belmont COM 7 is only -6dB on the PSB main muxes and in band for a very old group A Belmont aerial... though Belmont has needed a wideband for a very long time so other muxes would also likely be problematic if it were a group A aerial.
Waltham COM7 is more like -8dB on the main PSB, but outwith the passband of a group C/D analogue aerial... again though wideband has been required for Waltham for a very long time and other muxes ought to be close to borderline reception. Check the figures reported for all the mux frequency channels and it might give you some more ideas as to which transmitter you should be using.
DO also, go over all aerial cables and connections with a fine-tooth comb, remaking where needed; and keep hdmi leads well away from the aerial leads to give the weaker signal the best chance.
Did you mean "due to" a weak signal? It could be many things. An obstruction in the signal path (a distant lifting crane, a new building or a rapidly growing tree can reduce the signal.)
It could be the aerial that has moved or been damaged or got water inside.
It could be cable damage through abrasion, water or even heat from a boiler vent.
It could be a bad connection (cable plug or wall socket).
Most common is a faulty "fly-lead". See
http://www.satcure.co.uk/tech/freeview_problems.htm
Thanks for all the above advice, even if I hardly understood a word of it
I didn't mention that it is all being channelled through a Humax 2000T, which has had a recent software upgrade to resolve issues with certain channels. I'll wait until I've checked them all again before taking any further action.
NB Up until the latest firmware update the 2000T did not pass RF signals through to a TV in standby, only when fully powered up. That would make a big difference if the 2000T was in standby and the TV tuner was being used. If the TV worked at all you would have been very lucky (and living in a strong signal area).
Er, partially wrong!
Com7 for Waltham is on UHF 31. (approx 10kW)
UHF 26 is L-NOT (5kW)
BTW Belmont 33 is approx 37kW.
http://www.ukfree.tv/transmitters/tv/Belmont
http://www.ukfree.tv/transmitters/tv/Waltham
I should mention that I never watch the television without the Humax box being turned on, and that the recent update seems to have solved the problem of signal break-up.
The latter are 'universally available' on all the 1050+ TV transmitters in the UK the former (original 3 x COM muxes) are on the (cheaper to provide) 81 or so sites serving a (slightly) smaller population.
COM 7 (& 8 not yet on air) are on fewer sites yet than the original COMs using old pre-DSO kit and are 'temporary'. These are DVB-T2 HD ones intended to drive the uptake of mor modern receiving kit to enable a less-painful transition to a DVB-T2-only transmission system in the future.
The muxes are broadcast on different UHF frequencies from different transmitter sites to cover as much of the population, as best they can. Some locations have overlap from more than one transmitter just due to the natural topography and where transmitters are historically located.
So why are both Belmost and Waltham transmitting the same channels on both a COM and a PSB? How does the tuner know which one to save and which one to discard? I can search each number on both DVB T1 and DVB T2. I think all the HD channels are on DVB T2, but I can't be sure.
I think I'm confused about why you are confused! So this might not answer your question.
If you are asking how does a tuner know whether to choose the COM7 multiplex from Belmont or Waltham. It probably doesn't, and this is why - if you can - manually tuning your equipment is often required. Many tuners when automatic scanning will scan from UHF channel 21 up to UHF channel 69. It will see the COM7 multiplex from Waltham (UHF 31) before it sees Belmont (UHF 33). Some tuners will choose which COM7 based on the strength of the signal. Some choose the first one they see. Some tuners discard the duplicate and others might renumber the duplicate services on channels above 800.
This begs a question about your original post. You say you have manually retuned to try and get BBC 4 HD. Did you delete BBC 4 HD from the previous scan? Have you checked channels listed around 800 to see if you have a duplicate? If there is a BBC4 HD listed in the 800s, does it provide a better signal?
I tried manual tuning because of signal break-up, but it made no difference. The Humax box software upgrade seems to have solved this.
That one has BBC ONE HD, BBC TWO HD, BBC THREE HD / CBBC HD, ITV HD and C4 HD. No others (at the moment).
BBC FOUR HD / CBeebies HD is on the COM 7 mux on frequency ch33 from Belmont and ch 31 from Waltham.
Confused?
Rumours are that the 2000T firmware update improved the tuner sensitivity / gain control / metering in software so it may now be doing better 'level and quality' checks when choosing which one to store? But only Humax can tell you how their tuning / store algorithm actually works..