All posts by nickwilcock
Below are all of nickwilcock's postings, with the most recent are at the bottom of the page.
There was some information in the latest (5 Jan 2011) Ofcom document http://stakeholders.ofcom.org.uk/binaries/broadcast/guidance/tech-guidance/Central.pdf but no dates. (OX283SR)
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Ah, sorry, I thought your "I didn't notice that" referred to the 800 MHz plan - my mistake, it referred to the observation of your previous posting time!
As I understand it, Ch 61-68 will eventually be cleared, but no decision has been made as to when. Similarly, some juggling with the lower channels now means that in the 600MHz band only Ch31-38 will now be cleared and that Ch 39&40 will remain available for DTT.
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andy, the signal strength on most Freeview channels from Oxford is currently well below the value it will be after 28 Sep 2011. The power on some multiplexes will increase by a factor of about 900% on 28 Sep 2011.
So yes, atmospheric vagaries could well cause intermittent reception until then. Higher frequencies (e.g. Ch 68 as used for ITV1, Chan 4 etc) are also attenuated rather more than lower frequencies (e.g. Ch 29 as used for Yesterday, Film 4 etc.) and your antenna must be suitable for all the channels you wish to receive.
But after 28 Sep 2011, things should be much better!
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Whilst it's true that digital signals, when degraded, produce pixellation and sound blocking which viewers find unnatural - whereas analogue suffers from snow and multiple imageing. This is why DAB sounds so bad when the signal is weak - weird bubbling mud sounds instead of the background hiss which humans find less intrusive. But people have become so accustomed to high quality TV now, that even the slightest digital dropout becomes intensly annoying. But digital receivers have built-in error-correction systems which attempt to recover lost transmission segments and usually do so very successfully until they cannot cope as the signal drops off the 'digital cliff'.
However, Oxford Beckley's performance should improve massively with the power increase and frequency changes scheduled for September 2011.
Analogue signals in East Witney are pretty poor; however, I've been very impressed with the robustness of the digital signal, if less so with the unnatural artefacts that are a characteristic of many digital broadcasts. Hence the need for 'HD'; non-HD TV could have been broadcast in 'DVD quality', but commercial greed has pushed for quantity, not quality and we have a plethora of rather indifferent channels as the result...
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I'm an OX28 resident with a very old Group C/D antenna.
Digital reception is as follows:
Ch 29 (MuxD) - Very good
Ch 34 (Mux1) - Very good
Ch 48 (MuxC) - Good
Ch 51 (MuxA) - Good
Ch 52 (MuxB) - Good
Ch 68 (Mux2) - Medium
Given that most digital transmissions from Beckley are on reduced power, the signal I'm getting is fine.
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I guess the trees must have come out in leaf now and are attenuating high channel signal strength - my latest reception at OX28, East Witney with a very old Group C/D antenna, is:
Ch 29 (MuxD) - Very good
Ch 34 (Mux1) - Very good
Ch 48 (MuxC) - Good
Ch 51 (MuxA) - Medium/Good (was Good)
Ch 52 (MuxB) - Good
Ch 68 (Mux2) - Poor/Medium (was Medium)
Fortunately the picture quality doesn't seem any worse than before though - it's just the reported signal quality.
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So, having decided to transmit Oxford D3+4 on Ch 60, as well as moving Oxford SDN from Ch to 62 to Ch 50, we're now likely to suffer interference from whatever 4G is?
Ofcon strike again.....
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Are these filters 'no loss' devices?
Where are they to be fitted - at the antenna or at the receiver?
Anyway, surely error correction will take care of most interference? I suspect this will turn out to be similar to the 'FM-immunity' nonsense which cost many aeronautical VHF users hundreds of pounds thanks to CAA regulations - but no-one has ever noticed ANY 'FM' interference!
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Sunday 2 January 2011 9:31PM
Here in British West Oxfordshire, I'm currently receiving Freeview from Oxford. My UHF RF daisy chain to the kitchen TV is:
Ch 22 - Sky
Ch 28 - VCR
Ch 40 - DVR
There doesn't seem to be any mutual interference at present; however, although plans for Ch 29 (currently Mux D) are uncertain after 14 Sep 2011, I will perhaps have to retune the DVR to Ch 25 to keep it well out of the Freeview band from Oxford.
But with harmonics, intermodulation and other effects, there are bound to be some unexpected surprises lurking....