All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
charlo: BBC Local Radio is on DAB multiplexes that are operated by commercial companies. Thus, the areas that they are available is dictated by the areas that commercial broadcasters wish to serve.
The national BBC multiplex could never carry different stations in different areas because DAB does not allow it. It is a single service nationwide and is carried on the same frequency in all areas (a "Single Frequency Network").
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Jimb: No, the Commercial broadcasters in question do not wish to transmit from 1000 or so relay sites like Woolwich. They use about 80 to achieve a 90% coverage of the population. Their interest is viewers to watch advertising that they sell.
For a more in depth explanation, see:
Will there ever be more services on the Freeview Light transmitters? | ukfree.tv - independent free digital TV advice
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Derek Green: The "Poole" relay I referred to is at Parkstone. It will be a "lite" transmitter.
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Jimb: I think that the digital programme channels you have are likely to be coming from Crystal Palace.
To check, go to the signal strength screen whilst on ITV4 or Film4 and it may well tell you what UHF channel it is tuned to. For Crystal Palace it will be tuned to 29.
The Digital UK Tradeview predictor suggests that you will have a very good chance of receiving from Crystal Palace after switchover:
Postcode Checker - Trade View
This doesn't take into account local obstructions (trees, buildings etc) that may affect reception.
If you do decide to have your aerial replaced with one on Crystal Palace, then you will probably best to wait until switchover has completed on 18th April.
The current signals are weaker than they will be after switchover. An aerial that will work now (i.e. that will be sensitive enough to pick up the weaker signals) will be more than is necessary after switchover.
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John Illy: There is the power of the transmission; that is the strength of the signal as it leaves the transmitter. And there is the strength of the signal at any particular location.
If the signal that you are trying to receive at a particular location is "low", then it will be more susceptible to interference than one which is "high".
The higher the power of the transmitter, the higher the level of the signal will be at your location.
The sentence that you've quoted explains that the "low" level digital signal is more affected by "high" strength analogue [than if the local digital signal had been of "high" strength].
An analogy is if you talk loudly (the level of your voice is "high") then the reception of your voice will be less susceptible to interference from those talking around you. If you talk quitely (your voice at "low" level), then the person listening to your voice is *more likely* to suffer interference due to the person speaking at "high" level nearby.
The receiver of your conversation is hearing all voices in the area, and in order to hear you, yours needs to be at the receiver's ears.
The signal going into the receiver's ears is therefore the sum of all voices in the area, each having travelled to that location (and therefore lost some of their volume). The same goes for reception of electromagnetic (radio) signals.
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John Illy: My last but one paragraph should say: "The receiver of your conversation is hearing all voices in the area, and in order to hear you, yours needs to be *highest* at the receiver's ears."
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Paul Brown: Mux 1 is on channel 59 which is now used for a post-switchover multiplex at Midhurst (since last Wednesday) and also for Mux D at Tunbridge Wells. According to Digital UK Tradeview, Mux D on C59 is at 200W. The Ofcom guide to pre-DSO transmitters which was last updated two years ago, says that TW Mux D was at 100W:
http://www.ofcom.org.uk/s….pdf
Reigate uses channel 24 (same as Mux 2 from Blue Bell), and its power was increased on 7th March. I have seen suggestion by other contributors to this site that that was done to counter possible interference due to another transmitter, Rowridge, switching over to digital and using the same channel.
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martin: I apologise if my reply was somewhat flippant.
The only thing I will say is that in your general area receivers can sometimes tune to Rowridge instead of Whitehawk. The workaround is to run the automatic tuning scan with the aerial unplugged for the first 50%. This works because Rowridge uses low frequencies and Whitehawk high ones.
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Mark: If DAB+ is to replace DAB, is this the sort of thing that we will have to get used to?
DVB-T being replaced by DVB-T2 and so on?
Is it not possible to design in backward compatibility?
It means more "switchovers" to the newer systems.
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Monday 19 March 2012 7:26PM
martin: For Whitehawk Hill, all channels post-switchover are "in group", that is they are in Group C/D. This was the case before switchover, except for analogue Channel 5 which was on channel 35. So a wideband aerial is not necessary after switchover.
You will not pick up HD signals yet because they aren't being broadcast!
High definition services become available at the second stage of switchover, which for Whitehawk is this Wednesday.