Arqiva press release on Oxfordshire switchover
Brian Butterworth published on UK Free TV From Arqiva press office:
NEWS ALERT
Date: 28 September 2011
DSO completed for Oxford transmitter group
The Digital Switch Over process for the Oxford transmitter group, serving Oxfordshire and parts of Berkshire and Buckinghamshire, has been successfully implemented by Arqiva.
The public-service multiplexes are now being transmitted at full power from the main station at Oxford and, for the first time, from its five dependent relays at Ascott under Wychwood, Charlbury, Guiting Power, Icomb Hill and Over Norton.
The 'commercial' multiplexes (Oxford only) do not reach their final DSO powers until April 2012, as planned.
Following the analogue switch-off for BBC Two on 14 September, the remaining analogue signals for BBC One, ITV1, Channel 4 and Channel 5 ceased by 00:01 on Wednesday 28 September. The new digital signals entered official service at Oxford at 06:00, with the last of the relays completed by 12:33.
Help with Freeview, aerials?
In this section
Tuesday, 4 October 2011
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Chris.SE2:14 PM
Suzanne: so to be clear, when you have cleared all previous setups and double checked you have no channels (or in the 800's) and then do C59 alone and nothing else, you get zilch!
As I said, if there was a problem with Arq A (COM5) in the NNE/NE direction, I would have thought a lot more people would be complaining. But, I've just looked up the current power and it is restricted to 12.5Kw until April 2012, but so is Arq B (COM6) on C55 and SDN (COM4) on C62 and you are getting them OK (aren't you?), apart from which you are so close & line of site to the transmitter it should still be coming in 100% and they were only on 10Kw before the change in any event.
Back tracking to another thing you said in a previous post C55 was showing Quality 27, Strength 0 - was that correct and is it still the case? Also if you do a reset to clear the set and then do a manual tune of C55 only, does it give the same?
Anyway, don't give up, we will persist in getting to the bottom of this. Now your next door neighbours Sky should not be giving a problem in itself, but if their box has an analogue out and it's tuned to C59, then it's a possibility, but I would have thought unlikely. A simple check of them switching their box off for say 30 minutes whilst you rescan C59 should check that out, but be careful if you approach them on that, they could take it the wrong way, I'd leave it until last anyway!
Tim: I forgot to comment on you moving the coax about, but KMJ could be onto something, so I'll leave that to him :}
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Suzanne2:27 PM
Bicester
Chris: Thank you once again for more invaluable information. So the signal is NOT at full strength until April 2012..Hmm..they might have thought about this before moving those channels. Not impressed with them ;(
Reading a previous post recently: It was suggested the signal could be TOO much, as I'm only 8 miles from the transmitters. And I have a high-gain aerial, highest you can buy I think ( 52 something or other is it) forgive me, I'm really a novice to this. So I have just purchased a "Signal Attenuator" from Maplins arriving tomorrow. 12Db it said, gosh I hope that is okay, although the way things are going, I seriously doubt it.
But on the plus side you guys are really super helpful and hopefully we shall resolve this before April 2012..
Let me know your thoughts on my aerial etc. Oh yes, I have done everything thoroughly, clearing all set-ups previously, then trying manually to bring the "Elusive Ch59" into play..but yes, zilch!!
Thank you.
Suzanne
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Chris.SE3:42 PM
Well done with the attenuator.
Aerial - not a Triax Unix 52 by any chance, that's a CAI Benchmark Standard 2, good quality, it ought to say on your receipt! but it's not the highest gain (thank god, you're too close for them).
Hmmm, they are transmitting 2.5Kw more than before on the COM muxes, the PSB muxes are 100Kw. The Com muxes are due to go up to 50Kw next April.
Out of curiosity, have you got a bit of wire, old flex, speaker cable sort of thing about, say 6" to 2' in length. If so, try putting it in the centre of the coax socket on the back of the TV and see what sort of signal you are getting if anything.
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Suzanne4:15 PM
Bicester
Chris: Phew..at least I got the "attenuator" right, thanks.
My aerial: COMMTEL GOLD HIGH GAIN ++ DIGITAL TV AERIAL 52 ELEMENT GOLD KIT. Now if you want anything more technical I dare say I shall struggle, but will endeavor to do what I can if it helps. As for me placing wire into any socket, sorry "Coax socket" not sure that appeals, sorry rather girly about electrics.
I'm dreading what you're going to say about the aerial..I'm thinking may be the 'worse aerial I could have got' having said that my tv has an excellent picture..well apart from the channel I want..Ch59.
Suzanne
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Chris.SE5:26 PM
Suzanne: Don't be so negative! That aerial's a CAI Benchmark Standard 2 as well, so you're OK ;)
Perhaps if I use the words "Aerial socket" that won't sound so bad. It won't bite or electrocute you! just don't bend the centre contact. You could try just putting your finger on it, that sometimes works if the signal is strong enough, but at 8 miles probably not :)
Let's see if the attenuator sorts it.
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jb385:58 PM
Mike Dimmick: Although I see what you are getting at, in my opinion "if" an attenuator does solve the problem then I would be looking at it from the point of view that high powered D3&4 (Mux Ch60) is the cause of the problem by its sheer strength being on the verges of swamping the tuner, this having the effect of desensitizing the receiver for adjacent channel reception, which would of course seriously reduce reception possibilities of the low powered ArqA on Mux Ch59.
As you have said, this is one of these odd situations where a main high powered Multiplex is sited adjacent to a lower powered one operating on the same station.
Of course the other downside of adding an attenuator is, that it would also have the affect of slightly reducing the signal strength being received from the already low powered multiplexes, although what might be gained by slightly killing Mux Ch60 could possibly well compensate for any loses the attenuator might make.
Still, it will be interesting to hear what the result is.
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Suzanne11:03 PM
Bicester
JB: Just read your posting for 5.58PM today.
I apologize if my questions seem some what futile, but what is the point of an "Attenuator" if it affects all signals coming through the tuner..thus reducing the already lower signal on ArqA, Mux Ch59. As you point out it will reduce the signals on the perfectly working channels too. Or am I misunderstanding what you're saying.
I'm just starting to feel, that until the ArqA, Ch59 is up to full output, April 2012 there is probably very little I can do. I don't hold out much hope for the Attenuator, I don't know why, but something tells me I won't be watching the Lifestyle channels this weekend.
I find very interesting that you have questioned having the high powered Mux Ch60 next to Ch59 which could be swamped by higher signal output of Ch60. If you have considered this..then WHY hasn't Arqiva thought about this, especially with the strength not at full power yet. I shall report back once I receive the attenuator.
Suzanne.
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Wednesday, 5 October 2011
M
Mike Dimmick1:33 AM
Suzanne: At 13km from a 100 kW transmitter you need a 14-element Yagi, tops. A 'contract' 10-element would probably have been fine. An indoor aerial will probably work well enough at this location.
I have to say that aerial looks pretty flimsy.
The difference between C60 and C59 at the moment is only 9 dB, there was a much bigger difference between adjacent analogue and digital channels before switchover (e.g. Channel 4 on C53 and Mux B on C52 differed by 19.2 dB).
The problem is that digital TV requires any amplification to be very linear - including automatic gain control and the internals of the tuner. If not, you get intermodulation - frequency-shifted copies of the signal in one channel, that then interfere with another channel. Most amplification circuits are approximately linear - near enough for reliable performance - in their designed input range. Go outside that range and they distort. It's that intermodulation that I think is happening to you.
IF your fitter had set up the signal levels at the recommended level for analogue, they should not now be so strong as to cause intermodulation. However, many fitters either set up the signals at the maximums for low-power digital, despite the large difference in levels between analogue and pre-switchover digital at Oxford, or just fitted the same aerial everywhere regardless of the requirements of the location.
Some boxes might have trouble with very different signal levels between multiplexes, say if their gain control circuits set the level based on the overall signal level, but then I would expect all the commercial multiplexes to fail, not just one. I didn't see very many reports of problems at Sutton Coldfield between stage 1 and 2 of DSO, which had the new BBC multiplex booming in at 200 kW on C40 and the old ITV1 mux (Multiplex 2) at 8 kW on C41 - a difference of 14 dB.
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jb389:13 AM
Suzanne: An attenuator placed in line with an aerial socket "will" affect all signals passing through it, and there is no way of avoiding that happening, but in your case the attenuator might take the edge off Mux Ch60's excessive signal strength just enough to allow your TV's tuners sensitivity to rise to a level that will allow Mux Ch59 to be picked up, (hopefully anyway!) although variable attenuators are usually best in these situations as they can be fine tuned (so to say) for best results without killing off the channel you actually want to receive.
I admit to having overlooked the fact of high powered Mux Ch60 possibly coming into the equation, and it was only when Mike Dimmick referred to channel positions that it dawned on me that the whole problem could possibly be caused by tuner desensitizing, and is something I have even referred about to others in the past.
A comment that Tim had made would also back this theory up, that of him being surprised to discover that his Toshiba TV was found to operate OK when his Humax did not, with the likely reason for that being because sensitive tuners are more prone to being desensitized over the lesser types, and the Humax is much more sensitive than the type fitted in his Toshiba, a model that I am acquaint with as far as its receptive qualities are concerned.
High sensitivity tuners are great for being able to pick up a signal in difficult areas where other types are inclined to struggle, but this beneficial aspect of a good tuner turns into a detrimental one in oddball set ups like Oxford, where the powers that be have allowed a multiplex to operate on high power whilst another on the next channel is still operating on low power.
Of course its fully appreciated that people with aerials that's just adequate for reception and no more will not likely have any problems, whereas people that upgraded their aerials when low powered DTT first started very likely will.
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Suzanne11:02 AM
Bicester
Mike and JB:
Thank you for continued support and help. Okay, the attenuator has just arrived, but without any instructions. Yes, I can see plainly that one end is fitted into the tv the other, the aerial coax. But, here's my question, sorry guys: Before fitting it, should I do a Factory Re-set and clear all channels or do I not worry about that and just attach it, and see what happens?
From reading your TWO postings, it seems my aerial may be the problem, as it's a high-gain and receiving too much signal as I'm so close to the Oxford Transmitters. As Mike says probably an indoor aerial would have been okay being so near. At least that is what I understood he meant. So my Comtel aerial may be picking up too much signal, and you point out it looks "pretty flimsy" and suggest a Yagi 14 element would have been suffice. So shall I change the aerial IF the attenuator doesn't do the trick?
Thank you.
Suzanne
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