All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Ann: You aren't picking up C50 from either because they are corrupting one another. Your aerial faces Midhurst and so picks up some of its C50 signal. However, even in that position, evidently, it picks up enough of Horndean's C50 to render either unuseable. In essence what you have coming down your aerial lead is the sum of both signals.
Remember that the aerial is most sensitive in the direction to which it faces, and is less so in other directions. However, it is probably in such a location that the unwanted signal is so strong that the lesser sensitivity in that direction (than forward facing) is still sufficient to pick up that signal.
I doubt that attenuation would help. The problem is that you would be reducing the level of everything coming down your aerial lead. So now have you a "large" poor quality/corrupted signal. Attenuating it will give you a "small" or "smaller" poor quality/corrupted signal.
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W L PENDER: What transmitter are you using?
Digital UK suggests Salisbury may be the best. However, Rowridge is also good and only 30 degrees away from Salisbury at your location.
My guess is that the TV with issues is tuned to Rowridge instead of Salisbury.
Fortunately Rowridge uses low channels and Salisbury high ones, so (if you are on Salisbury) then run the automatic tuning scan with the aerial unplugged up to 50% in order to avoid Rowridge but get Salisbury.
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Robin Jenner: Where abouts are you?
There are a few areas where Midhurst's Commercial channels may be not longer receiveable. See for discussion of one such example location:
Freeview on Midhurst TV transmitter | ukfree.tv - independent free digital TV advice
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Nick: As far as the question of Sudbury or Tacolneston goes, assuming no local obstructions, the former would appear to be the much better bet.
I refer you back to my earlier posting to you on this:
Freeview on Tacolneston TV transmitter | ukfree.tv - independent free digital TV advice
Click the "Terrain between..." links for plots.
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John Chambers: Indeed.
The only thing I can suggest to you in the mean time is that, if your receiver allows manual tuning, you do so to UHF channel 28. This is the equivalent service from Crystal Palace and has been available since 18th April when it switched. You may be lucky and be able to pick this up to some degree until Sudbury's power goes up.
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Duanne: The transmitter in Leek only carries Public Service channels. This is because the Commercial broadcasters (that don't transmit from Leek) don't wish to spend the money on doing so. This is the case for nearly 1,100 similar small sites nationwide.
See here for an explanation:
Will there ever be more services on the Freeview Light transmitters? | ukfree.tv - independent free digital TV advice
If you are lucky, you may be in a location where you can pick up all channels from a main station that carries them.
If you are not, then Freesat may be your best bet for extra channels.
If you supply your location, preferably in the form of a post code or nearby post code, we can look up Digital UK's predictor which should give some idea of the likelihood of you being able to receive the Commercial channels.
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Duane: What can be received can really only be determined with an installer on site. Local obstructions such as buildings and trees can all play their part, but are not factored in to prediction systems.
According to the predictor, Sutton Coldfield is your next best bet. However, whilst its Public Service (PSB) channels (the ones you currently get from Leek) are "good", the Commercial (COM) ones are "variable" and "poor". This looks to me as thought the reason for this difference is down to the fact that the Moel y Parc transmitter uses the same three channels as Sutton Coldfield's Commercial ones, but not its Public Service ones.
Whether it will pose problems can only really be determined by an installer. You may find, for example, that something (e.g. trees) acts reduce the level of signal from Moel y Parc, thereby making reception of the COMs from Sutton Coldfield good. Also, aerials by their design, "reject" signals from other directions (other than to which they face) to a certain degree, so depending on what direction it is from may affect how good a new aerial will be at ignoring the unwanted signal.
Failing that, the COMs from The Wrekin are predicted as "good", although two of its PSBs are "poor". I can't work out which transmitters DUK thinks may interfere here*. If it did prove to be an issue, but the Wrekin's COMs were OK, then you could always combine your Leek aerial with one on the Wrekin in order to get the full complement of channels.
* Maybe Storeton or Ladder Hill are predicted to interfere with two of the Wrekin's PSBs, although they are vertical and Wrekin is horizontal, so the aerial will be at right angles to their signals, thereby helping to reject them.
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Duane: Sorry, it's probably not the simple answer you were hoping. This is the consequence of the quasi-national networks that the Commercial broadcasters operate. People such as yourself whose native transmitter is a PSB-only one obviously wish to receive all channels if possible. It may be possible, but there may be some length that will have to be gone to such as cost of a new aerial.
You may also find looking around at neighbours' rooves gives some ideas; see what transmitters they are using.
See Digital UK Tradeview for the directions of transmitters:
Postcode Checker - Trade View
Under "Aerial Group" H means horizontal, so aerials will be horizontal and V means vertical, hence aerials will be vertical, same as for Leek.
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jb38: Thanks for the interesting insight.
The topic is coming clearer to me.
I can see how trees and passing traffic may be an issue where they pass over the brow of the hill. The brow being perminantly flat means no change in the path of the signal. Moving trees or traffic effectively acts to vary the "brow" of the hill so that it is not flat and crucially is always varying.
What about polarisation of signals? Are vertical ones affected more than horizontal ones or vice versa?
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Thursday 26 April 2012 1:03PM
Robin Burnett: At just over a mile from this high power transmitter, your receiver could well be suffering from signal overload problems or at least the higher power (horizontally) Public Service channels acting to make reception of the Commercial ones more problematic.
I am wondering why you have replaced your aerial. The one used for analogue would be expected to work fine as all channels are within Group A.
The situation with Rowridge is that it now transmits horizontally and vertically. The Public Service channels (BBC, ITV1, C4, C5 etc) are 200kW horizontally and vertically and the Commercial ones (those you're having issues with) are 50kW horizontally and 200kW vertically. If you haven't done so, then switch your aerial to vertical.
You really need the smallest aerial you can get. Have a look at:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
With just over a mile, you may well find that a 20dB attenuator isn't enough. Perhaps you will need a high value fixed one (e.g. 24dB) and a variable 20dB one. Connect them inline and adjust the variable one.
One of the issues that is likely occur is that the high power signals will desensitise your receiver to signals that aren't as strong. This is like when your eyes desensitise when exposed to higher levels of light.
Don't get me wrong, at a mile a 50kW signal is very strong!!!