All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
delboy: My last sentence should say "Those in poor areas, such as low down or with obstructions, will be those who have the greatest probability of having issues."
| link to this comment |
michael: The reason for poor DAB coverage from BBC local radio stations is because they have to rely on commercial operators' DAB multiplexes.
BBC local radios' FM transmitters will be in places that the commercial broadcasters would never bother with because they don't see it as being worth their while. Whereas the BBC is a public service broadcaster and therefore spends money on transmitters with the objective being to increase coverage (and the amount it costs to do so not being top priority).
So BBC local radio on DAB is essentially at the mercy of the commercial strategy of placing transmitters. That is the objective of maximising the potential lister base in the most cost effective way possible.
It is the same reason why 9% of the population that can get Freeview cannot receive the full complement of services and why Classic FM's network of FM transmitters does not equal those of the BBC's equivalent national FM services.
| link to this comment |
Liz: It's a possibility that they're not quite strong enough to produce a picture on your receiver.
The one multiplex that you have, Mux B on C48, is the one that has the highest transmission power.
Are you using a rooftop aerial?
I'm not familiar with the local area, but the buildings on your road are four and a bit storeys (the "bit" on account of the fact that ground level is a bit below ground). I would have thought that with the aerial on the roof, there shouldn't be any problem getting a signal.
| link to this comment |
Liz: Have you tried manually tuning? If the manual tuning screen on your receiver shows signal strength, does it indicate that there is a signal there, but just too low for it to work?
For channel numbers, follow the link to Digital UK Tradeview next to your posting.
| link to this comment |
Liz: I've had another thought.
Where signals are high power and where some aren't so high power, a receiver can be desensitised by the high power signal, such that it won't be sensitive enough to pick up the weaker one(s).
An analogy would be eyes in bright light are desensitised. When in a room at night with the light on, it is not easy to see outside. Turning the light off makes ones pupils open up and take in more light.
If you have a signal booster, then you probably don't need it (unless perhaps the signal is split to feed multiple sets). You might need to fit an attenuator to reduce the signal level. Hopefully, if it is as I suggest (Mux B's strong signal), then you can reduce its level without diminishing the other multiplexes too much.
See here:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
Search eBay for <<variable tv attenuator>> Here is one such example:
LABGEAR VARIABLE DIGITAL TV AERIAL SIGNAL ATTENUATOR 0 - 20dB | eBay
You might be able to crudely attenuate the signal by plugging in the centre pin of the aerial plug only. You will probably only be able to do this if you have a non-moulded plug, i.e. you unscrew and remove the outer part of the plug. If this allows you to receive the missing channels, then you may be best advised to order an attenuator.
| link to this comment |
Liz: The fact that introducing the signal booster brings in all but one of the five missing multiplexes suggests that your problem is *not* too high a signal level as I suggested it could be. You may, therefore, have to leave it in until switchover.
How is your analogue reception?
Can you confirm that your aerial is pointing east towards Whitehawk Hill and is vertical (elements up/down)? Could it be directed at the Rowridge transmitter on the Isle of Wight? (If it is Rowridge it will be horizontal).
| link to this comment |
Louis: As part of the switchover process, services have changed channels (frequencies), and hence retuning is necessary.
| link to this comment |
Richard Gibson: Remove the signal booster, your receiver could be desensitised by the higher power signals.
I haven't seen anything to say that COM5 and COM6 are on lower power than what they were on before. Thus, that is why I would suggest that problem is caused by the higher power digital services.
The "desensitising" is a bit like your eyes being desensitised to poor light outside at night with the light in the room turned on.
Amplification could be unnecessary. See here:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
| link to this comment |
Tuesday 21 February 2012 9:41AM
colin1951uk: I'm not sure of the use of the "mandatory" !
But yes, it only affects the COMs. There are other transmitters that go through such changes for the same reason.
It is because the PSBs are allocated channels previously used by three of the four analogue services, hence they are available for use at full power (equivalent to that of the analogue services). But the COMs often use three channels that have not previously been used at a particular station, hence they only become available once any other transmitters whose signals might be interfered with have vacated those channels.