All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
sean: Chelmsford used to transmit only Channel 5 analogue but was switched off last July.
Due to all BBC standard definition services moving into a single multiplex after switchover, there are duplications between first and second phase of switchover. This happens at every transmitter during switchover.
BBC Four, CBeebies, BBC Parliament move to the BBC multiplex that was switched on at Crystal Palace on Wednesday. But they exist in the pre-switchover Mux B. The same is true for BBC radio.
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Paul: I put goodmans gdb3 into Google and the second link was to a Digital UK "Equipment Issues" leaflet for this model:
http://www.digitaluk.co.u….pdf
It won't tune to a multiplex that has a negative offset and is in 8k mode. Whether that means it will stall as it is doing I don't know, or maybe it would be expected to just miss out channels with negative offsets.
Before switchover all multiplexes are in 2k mode. After switchover the are in 8k mode. So BBC standard definition channels are now in 8k mode, but they don't have a negative offset.
On 18th April all standard definition multiplexes will have no offset except ArqB which carries Yesterday etc.
As for solving you problem, I came across the user manual here:
http://www.remote-control….pdf
It has "manual search" tuning so I presume you can tune manually. Try doing that by adding the following UHF channels: 23, 22, 32, 34, 29.
I assume here that you are receiving from Crystal Palace.
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sparky: BBC Four, CBeebies and BBC Parliament along with BBC radio stations will be duplicated between first and second stage of switchover. This is because before switchover they are carried in a different mux and at switchover all BBC standard definition services move into a single mux. Thus you have the new BBC standard definition mux (C23) and the old Mux B (C28). Go to the signal strength screen to hopefully identify which is which.
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Big Mart: Yes, they will disappear at the second switchover.
I'm not too sure whether different times of day makes a great difference. Evidently you're on the margin for HD channels which, BTW, before switchover are on lower power than standard definition channels and therefore have a smaller footprint of coverage.
After switchover all channels are on the same power.
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Sophiw: What's the make and model of your TV or box? Some won't work after switchover; the BBC channels have "switched" whereas the others haven't which is why I ask.
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AndyH: It's pretty likely that the situation will resolve itself on 18th April. Until then, keep manually tuning to C22.
Longer explanation:
Digital receivers have a signal threshold above which they will show a picture and below which they won't. For analogue receivers, the quality of signal is proportional to the signal strength and there is no threshold.
So let's suppose that when you previously received ITV, C4, C5 etc that the signal level coming down your aerial lead was "only just" above that which your tuner needs to resolve a picture. Now it is "only just" below that which it needs. The difference between the two may be quantified as being "tiny".
Perhaps with the other channels you were a "tiny" bit *above* "only just" having enough signal level and thus a "tiny" drop would leave you still with "only just" enough above the threshold and thus to use your description, "perfect" reception.
Signal levels vary a bit all the time due to changes in atmospherics.
Before switchover, digital signal levels are lower which means that whilst some will have good reception, others (on the outside of the transmission area) won't have any at all and those inbetween will sometimes have it and sometimes not.
For the ITV, C4 mux, with the aerial as you have it, you are evidently borderline now. The situation will change on 18th April.
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Aaron: There are two main possibilities I can think of here:
1. Some older receivers cannot resolve the mode of the post-switchover signals, of which the BBC channels are broadcast in now. The mode used by them is known as 8k mode and before switchover transmission use 2k mode.
What's the model number?
2. At 3 miles away from the transmitter, your receiver could be suffering from signal overload due to the strength of the signals. BBC channels are now on their post-switchover high power, the rest will follow likewise on 18th April.
For more information and an explanation, see Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
If this turns out to be the problem, then get yourself an attenuator for a few pounds.
I would rule out number 1 first and then assume number 2. Try manually tuning to UHF channel 23 if your set allows manual tuning.
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MRW: The transmission power of the Commercial multiplexes from Rowridge, which include ArqA and ArqB, will increase on 18th April.
I am note sure whether there were any changes to ArqA and ArqB that would have been to your detriment that took place on 21st March.
There is probably little you can do in the mean time as well as little point as the situation will change on 18th April.
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AndyH: It is surprising that you get nothing on C22.
The Tradeview predictor for your post code says 92% served for C22 whereas the other standard definition pre-switcher multiplexes are 99%. There must be a reason that it has calculated it like this. There appears to be no other transmitter on C22 that could be interfering at your location.
I can only think that perhaps CP throws out in your direction less signal on C22 than on the other pre-switchover channels. Thus the contrast between the low C22 and C23 may be greater than another side of the transmitter that throws out more signal on C22.
Based on the predictor, try tuning to C41 for the equivalent multiplex from Sudbury and Rouncefall (which broadcast this together on the same channel as a single frequency network). This might give you some degree of service until 18th April.
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Thursday 5 April 2012 8:05PM
Ray Buck: To clarify my first paragraph, what happens is the scan progresses and stores the channels as it finds them. This includes channels from transmitters other than the one you want. Then it gets to the channel(s) used by the transmitter you want by which time there isn't any memory and, evidently, these Philips receivers don't have any "intelligence" to disguard those channels you don't want in order to store some of those that you do.