All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Damian Cooper: Be aware that the Kilkeel relay also uses vertically.
We don't know what direction they it transmits as the powers that be won't release its radiation pattern. My guess is that it will be transmitting in the direction of Kilkeel and further up the coast to Ballymartin and Annalong. I should imagine that there is little point in it transmitting over the hills and so maybe it only broadcasts roughly between 3 o'clock and 6 o'clock
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Damian Cooper: Kilkeel also uses C39, although I'm not convinced that it will be an issue for you, although keep it in mind because you never know.
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mrdtv: The diplexer that splits at C51 will attenuate C52 about 4dB. This might not be an issue if the signal is sufficiently strong or if there is an amplifier, it might be sufficient or be able to be turned up a bit to compensate.
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Joe Faulkner : The COM channels don't have as good a coverage as the PSBs. 1,000 or so small relays don't broadcast them, and those that do broadcast them don't spread them as widely as they do for their PSBs. The COM channels are re-used by transmitters in closer proximity than the PSBs and this appears as if it might be the case at your location.
The COMs from Darvel, Divis and Caldbeck are all co-channel and at half-power to their respective PSBs. The Digital UK Postcode checker even "thinks" Divis is the best transmitter for you. This suggests that the possibility of reception of Darvel COMs is limited by interference rather than limited because it doesn't carry as far.
For this reason, I don't think that you will be able to receive COMs from Darvel. The PSBs of Darvel and Divis are not co-channel.
If you can receive PSBs from Girvan which is 20 miles away and are at only 50W, then you may be able to turn your high-gain Group A aerial to Divis and combine with a Girvan aerial to give you BBC Scotland/STV regional output and COMs.
The only warning I will give you is that recorders can have difficulty with timed recordings when receiving from two different transmitter regions, the reason being that the EPG information isn't shared between the two. If this turns out to be the case then you will have to decide whether to have your recorder on one or the other (i.e. Girvan PSBs only or Divis PSBs+COMs).
If you can receive from Girvan, then you will need a diplexer to combine feeds:
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Girvan uses 50, 59 and 55 so the model that "splits" at C38 will be best. This will also allow reception of Divis PSBs as all its channels are below 38.
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Christine Ratcliffe: You would appear to be receiving from Waltham rather than Nottingham. Waltham is undergoing engineering works which may affect signals. You may or may not have been suffering poor reception for a longer period.
Winter Hill also broadcasts high power on UHF channel 61, although I'm not so sure that it might be the cause of your woes.
The terrain plot shows that the path between the transmitter and you is close to the ground for the final few miles which could be a source of issue:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
I see that other houses in the area have tall masts and large aerials which are probably a sign.
I'm not an installer, so the professionals may be able to add to what I'm saying.
Refer to the plot and imagine that the signal line is a light. With the path being close to the ground, objects such as trees and buildings could potentially be in the way. You know what happens when it gets near the end of daylight and the sun is low in the sky which causes long shadows.
Intermittent problematic reception caused by such reception can affect only one or two frequencies. Moving the aerial may be the only way - it is a try it and see thing I believe.
The only other thing I can wonder (as I say, I'm not a professional) is whether because your aerial is looking over your roof-top with the chimney not being immediately in front, but perhaps at 30 or 40 degrees to the direction the aerial is facing is whether when these get wet that they cause reflections such that it degrades the BBC frequency.
I note on Streetview that your roof tiles were replaced in 2009. I don't know whether that might have any bearing, e.g. whether newer tiles are more likely to be reflective, perhaps helped by them being wet.
"If" any of these (roof tiles or something else on your roof) is the cause of the issue, then perhaps mounting the aerial on the gable end that faces the transmitter. I say "if" because it could be some effect (reflection or refraction) that occurs further away from you such as if vegetation is in the way, and for that the solution is much more difficult.
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Graham: There's no such thing as a "digital" or "analogue" aerial. An aerial is an aerial.
For Belmont, the four analogue channels were in Group A (bottom third) and consequently Group A aerials may have been fitted. COM5 (Pick TV etc) and COM6 (Film4, Russia Today etc) are high up in C/D (top third of channels).
This terrain plot shows the drop you live in:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
If the "analog" (sic) aerial is a Group A one and you are receiving COM5 and COM6 fine, then that must tell you something. It is less sensitive and less directional on those higher channels and they are picked up fine.
A higher gain aerial is so because there is a narrower acceptance angle. That is, if you used it to transmit (send out a signal), the beam width would be narrower.
When you can see the transmitter, or aren't far off, then such an aerial can be focused on the beam from the transmitter. Maybe the issue you have is that your "big" aerial has too narrow an acceptance angle. Or alternatively, maybe it is situated in a dead spot.
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Dave: If that is the impact that it may have on TV reception, what might be the affect to the health of those living in such fields?
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George: If you are "practically on top of the mast" then WHY ON EARTH have you got a high gain aerial and a mast head amplifier???!!!!
Surely you would not need any let alone one!!
Freeview signals: too much of a good thing is bad for you | ukfree.tv - 10 years of independent, free digital TV advice
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Judy: I can't say for definate, but the retune on Wednesday obviously meant that the service was interrupted.
Perhaps the message you've quoted relates to that change and not some other work that is to be carried out but refers to the whole week rather than the day of the change.
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Wednesday 21 November 2012 8:30PM
joanna carney: Perth is in a valley which means that it can't "see" the Angus transmitter near Dundee.