All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Mick: Only you know why you make yourself "put up" with receiving only the Public Service channels from Stroud!!
The reason is because the Commercial broadcasters do not have a "Public Service" obligation. They operate on a profit-driven basis and the cost of including over a 1,000 small transmitters in their portfolio would outway the benefit (as far as they are concerned).
The 81 transmitters that carry the Commercial multiplexes are the largest, by viewer population. This achieves 90% coverage of the population. To include the 1,000 plus relays would roughly double the cost of transmission whilst only adding about 8.5% of the population to the Commercial broadcasters' viewer bases. Clearly they don't see that as a worthwhile investment when they are in the business of selling advertising to generate revenue. That is, they don't consider the additional number of viewers to be worth the cost as far as attractiveness with advertisers is concerned.
It is unfortunate that the Stroud transmitter uses channels that are interleaved within the Commercial channels from Wenvoe as you could have had a second aerial installed on Wenvoe and combined them into one downlead to give you no Welsh programmes and the Commercial channels.
If you provide your location, preferably post code or nearby post code, then we might be able to suggest what the likelihood of receiving from another transmitter might be. The Slad transmitter covers a small area as it is only 2W, but it does broadcast on channels that could be combined with those of Wenvoe (if there is a location where both can be received).
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Rog: The three Sandy Heath COM multiplexes are "out of group" as far as the old four analogue channels are concerned.
This means that where such an aerial is fitted, its senstivity at the frequencies used by the COMs will be less than that of the other (Public Service) channels.
The four analogue channels were on Group A channels (frequencies). Group A is the bottom third of the band. Consequently, Group A aerials were fitted whose sensitivity is best on those channels and drops off on higher channels.
The COMs are at the high end of Group B and this Group is the middle third of the band.
Prior to 9th May, COM4 was in a channel in Group A, so such an aerial would probably have worked.
A Group A aerial isn't forced to mean no reception of the COMs. It will mean at least lower strength being indicated on those channels, but with digital strength isn't so important (it's quality that matters).
So long as the signal is strong enough to be above the threshold that the receiver requires to resolve a picture, then it will work. And so long as it is far enough above that threshold that any natural reduction in strength (e.g. caused by the weather) doesn't put it under, then there will be reliable reception.
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COM4 is on UHF channel 51, COM5 is on C52, and COM6 is on C48.
If your receiver has manual tuning, then try manually tuning to these three UHF channels. Some devices give more clues than others. Some will give a strength for a chosen channel and if yours works like that, then it might say that there is a signal there, but that it is too weak to resolve a picture. Or it might be sufficient and allow you to add missing services.
If you have more than one receiver, then it might be worth trying others due to the different functionality of devices that I mentioned.
You could try doing this with and without the aerial fed through other device(s). For example, if you have a TV with built-in Freeview and a Freeview box (e.g. recorder), then try tuning the TV with the aerial looped through the recorder and then with it directly to the TV.
Once you have a device tuned, then don't retune it if you then get "no signal" on some or all COM channels (e.g. if you change the configuration of the aerial leads). In that case the receiver is tuned and it is an issue with the signal fed to it.
If you have a booster, then try with and without. The stronger strength of signals after switchover means that some boosters are not needed now, and if used could give too much signal. With digital, too much signal will be indicated by receivers as low or no signal (just the same as low or no signal).
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Chris: The Northern Ireland Mini-Multiplex that will carry RT will come on air at the completion of switchover on 24th October.
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Brian: There has been engineering works in preparation for switchover.
Don't retune if you have difficulties as these won't be caused or resolved by retuning and you may end up loosing affected channels from your receiver altogether.
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Laura: I had a look at your road on Google Streetview and can see that residents have difficulty with reception. I couldn't spot a single aerial on the Brixham relay; all are on Beacon or Stockland.
jb38, KMJ,Derby, this would appear to be one where the predictor isn't very helpful, other than to indicate the directions of the transmitters.
Laura's road is lined by bungalows and is on a slope. Beacon Hill is in the direction up the slope and at the end of the road (the highest part) are two houses.
I don't think that there's much point in trying with a set-top aerial or piece of wire.
I suggest that you confirm that the channels tuned are those of the transmitter to which the aerial faces. The information as to which UHF channel is tuned is usually given on the signal strength screen.
For each of the following, check the UHF channel tuned to:
BBC One --- BH=C60; SH=C26; B=C43
ITV1 --- BH=C53; SH=C23; B=C50
BBC One HD --- BH=C57; SH=C29; B=C46
ITV3 --- BH=C42; SH=C25
Pick TV --- BH=C45; SH=C22
Yesterday --- BH=C51; SH=C28
BH is Beacon Hill, SH is Stockland Hill and B is Brixham.
As an example, go to BBC One and bring up the signal strength screen. Note which UHF channel it is tuned to. If it is 26, then the signal is coming from Stockland Hill. If your aerial points to Beacon Hill, then that needs putting right.
- If your aerial is on Beacon Hill and you find that you are picking up some or all signals from Stockland, then a workaround is to run the automatic tuning scan with the aerial unplugged up to 30% (or up to UHF channel 33 if it gives them during its scan). If you do do this, then having done so, check that you haven't picked up the two (or three) multiplexes from Brixham (by carrying out the procedure outlined above).
- If your aerial is on Stockland Hill and you find that you are picking up some or all signals from Beacon (or Brixham), then run the automatic tuning scan with the aerial plugged in and then unplug when it gets to 30% (or when it gets to UHF channel 33 if it gives them during its scan).
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Rog: I'm inclined to suspect that you have a Group A aerial and that it isn't sufficient for the out of group COM channels.
The solution is probably a replacement aerial of the "wideband" type. Alternatively, a second aerial for higher frequency channels, combined (using a diplexer) with your existing aerial.
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Rog: I can't explain why you may have received all channels; there would seem to be no logical explanation.
The full list of Freeview channels can be found here: DMOL Post-DSO Multiplex Channel Allocations
Those with a bullet and grey background in the "E" (England) column are those which apply.
Prior to 9th May, you could probably pick up COM4 because it was within the frequency range of your aerial (i.e. "in group").
COM5 adopted its current frequency on 23rd November and COM6 did so on 14th September (both last year).
With analogue, every transmitter used four channels. With the full Freeview service, there are six channels required. Most transmitters have been given channels that are within the range of frequencies that former analogue aerials are likely to work, which means that existing aerials will work fine.
In some cases, however, including with Sandy Heath, this has not been possible and hence aerials may need to be replaced.
The reason for the retunes is because not all transmitters switch at the same time and therefore in some cases there is a delay before certain channels become available. Some have restricted coverage and/or use temporary channels until their final one becomes available.
Following the retune on 9th May, COM4 is now on C51. The wait was due to the fact that Hemel Hempstead was using it until it switched over to digital in April.
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c macdonald: There is quite a bit of overlap of the signals from Moel y Parc and Winter Hill transmitters. Consequently it is not uncommon in your area for receivers to tune to the wrong one.
I would check that the receiver is tuned to Winter Hill for all channels and not Moel y Parc for some (or all).
On ITV4, bring up the signal strength screen and if it is tuned to Winter Hill, it will say that it is tuned to C55 whereas Moel y Parc is C48. It's possible but doubtful tjay you could be picking it up from one of two other transmitters on C29 or C50.
If you find that ITV4 it is not tuned to C55, then that is the problem if the aerial doesn't face Winter Hill which is east north east from your location.
As a workaround, try running the automatic tuning scan with the aerial unplugged up to 65%. If, after doing this, you are missing channels and your receiver has manual tuning, you may be able to restore them using manual tuning. For Yesterday,ITV4 and others, it is 55.
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c macdonald: My penultimate paragraph should say that if ITV4 is not tuned to C55, then that is the problem if your aerial DOES face Winter Hill.
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Monday 4 June 2012 10:01PM
David Hemsworth: Lost channels after powering off is usually down to the receiver's memory being full. During the automatic tuning procedure, it scans frequencies from low to high. When it finds a signal, it stores it, and this includes signals from other transmitters (where they are present).
Consequently, where there are other lower signals present, and the ones you want are at the higher end of the band, the highest ones could suffer from being "forgotten". The workaround is therefore to get it so that it doesn't store the lower channels that you don't need.
This is the theory and you will have to test to see if that is the cause of the problem in your case.
I assume that you are receiving from Heathfield. What I suggest that you do is run the automatic tuning scan with the aerial unplugged up to 50% (or up to UHF channel 44 if it gives them when scanning). That way you will have it unplugged when scanning other transmitters. This will miss out ITV1, Channel 4 etc from Heathfield, but I'll come to that in a moment.
The test is to see if preventing other (non-used) signals from being stored will allow BBC to be stored. So power the set off as you would normally and then on again and see if it has remembered the channels it normally forgets.
If it has, then, if it has manual tuning, go to it and tune to UHF channel 29 to restore ITV1, Channel 4, Channel 5 etc.
If this works, then come 13th, start the automatic tuning scan with the aerial unplugged up to 35%. There should be no need to manually add any channel because they will all be in the window above 35%.
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ArqB multiplex which carries Yesterday, Film 4, ITV4 and others is as it was. The apparent lower strength may be due to the fact that the high power BBC multiplex is on a neighbouring frequency. The high power signal could be desensitising the receiver to the lower power ArqB signal.
It's like being out when it's dark when there are car headlights shining towards you. Your eyes will become less sensitive and it will be more difficult to see what's going on around the lights.
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And finally, there will be another retune event on 27th June when the SDN multiplex which carries ITV3 etc changes frequency. Until then, its transmission power will remain as it is now. You may find that it appears weaker, for the same reason as ArqB is now; that is the new high power signals will be on adjacent channels.