All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Malcolm Wood: See Digital TV Transmitters and other parts of the ATV site for information.
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julie: What you have described - the penny has just dropped!
The booster is probably on the roof as you say that the thing that has the adjuster is on the roof.
I suspect that what you are describing as the booster (the one behind the other TV) is in fact the power supply for the booster (on the roof) and not a booster itself. Try turning off the power to what you believe to be the booster. If it is in fact the power supply for the booster on the roof, then I would expect all signal to be lost, including on the Matsui as a booster with no power going into it won't have any signal coming out of it.
Therefore the two leads are connected to the booster on the roof.
I think that you need to get the installer to look at it. If there is too much signal, which there could be, then he will know what to do.
As for why one works when the other doesn't - different sets have different tolerances.
You're going about this the wrong way, if I may say so. If the signal is excessive, which judging by the power increase (before vs after) from Dover, it could be, then that needs fixing. Trying to find a television that will tolerate excessive signal is not the answer.
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Gordon Ormston: Confirm that it is tuned to C50.
If that doesn't fix it, then I would suspect that the signal level being fed into it is now too high and is in need of attenuation.
See Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
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Gordon Ormston: The high power post-switchover signals are such so as to provide equivalent coverage to that of the former analogue (at least for BBC, ITV1, C4, C5 and other Public Service channels).
Due to fewer frequencies being available, transmission powers had to be kept down so that they could be re-used by transmitters within a closer proximity than they otherwise would have been. Also, power was low so as not to interfere with analogue transmissions already on air which were co-channel.
In essence, it was a quasi-national network; i.e. there were gaps in coverage which is why we have a "switchover" and not just a "switch-off" (of analogue).
I assume that they covered as much of the population as they could with this network giving greater preference to those transmitters with more viewers (the assumed objective being to cover as many as possible). In any case, international clearance would have had to be granted with any signals along the coast being more likely to affect the continent.
So there was probably little that could be done if the pre-switchover service was to be crammed in.
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See ukfree.tv - independent free digital TV advice
A variable attenuator such as that shown on that page will cost £3 or £4 from online sources such as eBay. These are usually 20dB ones.
As an example (others are available!) I found this one:
VARIABLE ATTENUATOR TV SIGNAL REDUCER 20dB 3 5 6 9 10 12 15 18 DIGITAL FREEVIEW | eBay
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julie: I wish you well in getting it sorted.
I'm sure that the problem will be easily rectifiable by the installer.
Tell your mum not to worry. Her TV viewing will continue thanks to your efforts and she is lucky to have such a caring daughter.
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Andrew Walter: There is always the possibility that you need even more attenuation than you have. Perhaps connecting two attenuators inline with one another, one of them being a variable one.
The mast head amp needs removing, no doubt. With it in installed, its the signal from the aerial could be too high for the amp to cope with. Thus the signal will distort at the amp.
So the output of the amp will always be distorted. Adding attenuation will therefore give you a smaller distorted signal.
To pick-up less signal, whilst tuned to C50, try a 12 to 18 inch piece of wire inserted into the inner part of the aerial socket. Or use a set-top aerial. Or, as a crude attenuator, try your roof top aerial with a section of the screening removed so as to "loose" some signal.
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Debby: See my posting immediately before yours which answers your question.
ITV3, 5* and 5USA are all carried on COM4 multiplex.
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Trish Stygle: The Chartham transmitter currently carries only BBC services, which is what happens at the first stage of switchover.
At the second and final stage on 27th, the rest come on air. Until then, ITV and Channel 4 continue to be available in analogue, as does BBC One.
The bad news is that Chartham will only carry Public Service channels which are BBC, ITV1, ITV1+1, ITV2, Channel 4, Channel 4+1, E4, More 4, Channel 5 and the four HD services. Furthermore, aerials installed for Chartham which are Group A ones will be expected to work fine for digital and therefore a wideband aerial is unnecessary.
To get more channels, you will have to investigate how likely you might be able to receive from another transmitter that carries them, such as Dover.
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Thursday 14 June 2012 9:12PM
Malcolm Wood: Looking at those trees on the slope, I suppose that rules out Heathfield. Maybe you have already been along this road...
There seem to be quite a few houses on Sandcroft Road receiving from Dover. The problem there is that the COMs are half power to the PSBs, plus the COMs use a less robust signal mode (less error correction).
I suppose that you had a wideband aerial installed for Hastings so as to receive digital TV (because two were out of group). I sympathise as it looks as though you are going to have to change it again (if indeed there is a possible solution) or Freesat may be your only option for additional free-to-air programmes.
I'm not an aerial installer, so I wouldn't like to gauge as to your chances of success.
However, yagi wideband aerials' gain levels are lower at Group A channels, of which Hastings uses exclusively now. See for examples:
Gain (curves), Again
Your aerial is stuck up above the roof-line, and you're probably going to tell me "it needs to be". You're also higher than others which is a pity.
As I say, I'm not sure of the likelihood of success, but in situations such as this, the only thing to think about is is there somewhere where the aerial could be mounted where it will get sufficient signal from the desired transmitter and where it will be shielded from the interferer?
Even if there is somewhere suitable, the spanner in the works may be objects around you reflecting the interfering signal towards your aerial, if it is strong enough.
Assuming that you have no local obstructions, then this plot suggests that you can see the top of the transmitter mast:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
The only possible fly in the ointment to mounting the aerial lower that I can see are the trees around the edge of the recreation ground behind you.
But if you can get line of sight, then that is good for a high-gain aerial, as it can be pointed at the beam. The higher the gain of an aerial, the smaller the acceptance angle is (although obviously they all pick up from all angles to varying degrees).