All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
stuart smith: There may be another possibility and that is that you may be able to receive from the Greystoke relay transmitter. This carries PSB channels only, but you will be no worse off, not at least until October. It's only really low power of 2.3W, so if you don't have line of sight, then you really don't have a chance. You will need your aerial to be vertical. If it is a wideband aerial it will be suitable.
It may also be worth checking that your receiver isn't tuned to Greystoke even though the aerial faces Caldbeck. That is, that you aren't thinking that you're receiving Caldbeck when in fact you're picking up Greystoke.
You do this by viewing the signal strength screen. On BBC One for Caldbeck it will be tuned to C25 and Greystoke C60. For ITV1 Caldbeck is C28 and Greystoke C53.
The reason I came across Greystoke transmitter is because I looked on Google Streetview. The Google car has not been along the roads in your post code, but only along the main roads in Greystoke (Icold Road, Berrier Road etc). I spotted vertical aerials and wondered at what transmitter they are pointing.
As I say, Greystoke transmitter is so low power that if you can't see it, you aren't likely to be able to receive from it. You may have a better idea whether you can or can't see it from where you are.
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Adina: I looked at your earlier postings and noticed that your aerial is pointing to the Woolwich transmitter.
This is a Public Service Broadcaster (PSB) transmitter only which means that it carries only BBC, ITV1, ITV1+1, ITV2, C4, C4+1, E4, More 4, C5 and the four HD services. If your receiver picks up any of the Commercial channels (ITV3, Pick TV, Yesterday etc) then they are being broadcast from another transmitter and therefore are being picked up with the aerial being in the wrong direction and wrong polarisation so reception may be hit and miss.
What you need to do is ensure that you are tuned to the Woolwich transmitter for the services it broadcasts and not another transmitter such as Crystal Palace.
One reason that your TV may tune to Crystal Palace is because its signals are at the low end of the band of frequencies used for TV. So when it performs the scan, it "might" simply go with the first one it finds. Not all receivers do it this way.
If your aerial faces Woolwich, then what you need to do is go to BBC One and bring up the signal strength screen. Hopefully it will say what UHF channel (equivalent to frequency) it is tuned to. For Woolwich it will be C60 and for Crystal Palace it is C23. Do the same for ITV1. For Woolwich it is C57 and Crystal Palace is C26. If the receiver picks up HD services, then they are on C53 from Woolwich and C30 from Crystal Palace.
If any of these are wrong, then you need to correct them. Because Crystal Palace is at the low end of band and Woolwich is at the high end, you should be able to have the aerial unplugged for the first part of the scan to avoid Crystal Palace; say plug in at 60%. Then check again to see that BBC One and ITV1 are tuned to the channels used by Woolwich.
You will be missing the Commercial channels; those which Woolwich does not broadcast. If your receiver has manual tuning, you may be able to tune in those from Crystal Palace, although you should be mindful that reception of them may be poor because the aerial is facing the wrong way.
For the Commercial channels from Crystal Palace, ITV3 is on C25, Pick TV is C22 and Yesterday is on C28. The programme channels are broadcast in groups, so for each of these three channels, there are others; I've just given you the first service carried on each channel.
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Tony: No, see the Wooburn page:
Wooburn digital TV transmitter | ukfree.tv - independent free digital TV advice
You may be lucky and be able to pick up the Commercial channels from another transmitter such as Crystal Palace or Hannington.
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Brian Smith: I suspect that the main issue that you have is the difference between the relatively low level and the high level signals.
The Public Service Broadcaster (PSB) channels that you have (BBC, ITV1, ITV2, C4, C5 etc) are at higher power horizontally than the Commercial (COM) ones (ITV3, Pick TV, Yesterday, Film 4 etc).
Before switchover Rowridge broadcast only horizontally. After switchover, it broadcasts in both polarisations.
The PSBs are at a transmission power of 200kW horizontally and vertically, whereas the COMs are 50kW horizontally and 200kW vertically.
Whilst 50kW probably doesn't mean a "weak" signal at your location, it is probably the marked difference between the two that is causing you difficulties with your receiver.
The strong PSBs are probably acting to desensitise the receiver, making it more difficult to pick up the nearby (weaker) COMs. This can be likened to bright car headlights in the dark reducing the ability to see the darker surroundings.
You could try connecting an attenuator inline with the aerial lead to reduce the level of the signals. A variable one will allow you to adjust. Of course it would be reducing the level of all signals (the stronger PSBs and the COMs). The objective would be to find the sweet spot (if it exists) where the PSBs are attenuated enough (to increase the sensitivity of the tuner) but where the COMs aren't reduced too much that they are too weak to be picked up.
Manual tuning is helpful here. Having got the PSBs tuned, your objective is to adjust the attenuator and then try manually tuning each of the three COM channels. If there is no manual tuning, every time you adjust the attenuator, you must complete a full scan (which obviously takes longer). If there is no manual tuning, but a way of scanning for new services, then this might be the best option as it won't wipe the PSBs you already have stored.
The attenuator route is a potentially cheaper if you will have to get someone in to change the aerial. However, it's not guaranteed.
You can pick them up for £3 or £4 online from sources such as eBay and Amazon.
As for the question of why it worked before 18th April; I can only wonder if it was due to the fact that the frequencies used by the low power COMs were further away from the PSBs. Now they are on neighbouring channels (i.e. each COM has a PSB on an adjacent channel).
jb38, does this sound as if it might be right?
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Col: If you don't wish to subscribe to Sky, there is Freesat available. You use the same satellite dish to receive it. There are differences in what channels are available.
See: Compare Freeview and Freesat TV | ukfree.tv - independent free digital TV advice
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Gareth Williams: If your aerial is facing the Micklefield transmitter, then you should be aware that it only broadcasts Public Service Broadcaster (PSB) channels. These are BBC, ITV1, ITV1+1, ITV2, Channel 4, Channel 4+1, E4, More 4, Channel 5 and the four HD channels. The Commercial broadcasters (known as the "COMs") do not wish to be bothered transmitting from those stations that reach potentially relatively few viewers.
If you are picking up any of the COMs, then you are not getting them from Micklefield. Because you are receiving them from another direction to which your aerial faces (and probably different polarisation), it is to be expected that poor or intermittant reception may ensue on those channels (if at all).
What you need to do is ensure that the PSBs that are tuned are those from Micklefield. It could have been the case that those which you are viewing were/are not from Micklefield. Did you check?
For BBC One, bring up the signal strength screen and for Micklefield it will be tuned to C57. Likewise for ITV1, it is C60. If your set is HD, then those are on C53.
Click the Digital UK Tradeview link next to your posting at it will show you the transmitters that are likely to be available to you and which UHF channels they broadcast on. That way, you can identify which transmitter(s) you are picking up.
See under the head "After switchover configuration" here (might need to refresh it once loaded to see the graphic):
Freeview multiplexes | ukfree.tv - independent free digital TV advice
This shows which services are broadcast on each multiplex. The best thing is to focus on the first service in each rather than trying to check each service individually, i.e. BBC One, ITV1, BBC One HD, ITV3, Pick TV and Yesterday.
If, let's say, you are picking up the COMs, then maybe you are getting them from Crystal Palace. The PSBs aren't forced to be tuned to the same transmitter, but let's suppose that you find that they are (i.e. 23, 26 and 30[HD]). Because Micklefield's channels are high up, and these are low, you can avoid them by unplugging the aerial for part of the scan. The scan runs from channels 21 to 69, so if it gives only a percentage, you can convert. I suggest that you plug in about 60%.
Note (see Tradeview) that if you are picking up from High Wycombe, it uses channels within the Micklefield range, so this will be more tricky and you may have to manually tune.
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Adina: How did you get on?
If your aerial faces Woolwich, then the best you can hope for is that the Public Service channels (those which it broadcasts) are good. You may need to do some work (as I suggested yesterday at 12:58) to get your TV/box tuned to them rather than their counterparts from another transmitter. You could add the Commercial channels from another transmitter (probably Crystal Palace), knowing that they may be poor or unavailable when you wish to watch something on them (but there's nothing more you can do with an aerial facing Woolwich).
"If" you have an aerial installed that will receive from Crystal Palace, then you will be able to pick up all of the Commercial channels (they are the channels that which Woolwich doesn't broadcast). As the Public Service channels that Woolwich does broadcast are the same as those of Crystal Palace, then there is no need for the Woolwich aerial and you would therefore receive all channels from Crystal Palace.
A predictor cannot say for certain either way whether reception is possible or not at a particular location as there are many factors involved. Such a system should is more a guide than gospel.
Whether you can receive from Crystal Palace and what sort of aerial (size) you will need can really only be determined by an installer testing whilst on site.
The reason you have this problem (where you can't get all channels from your native transmitter) is because those that you don't get are operated on a purely commercial profit-driven basis. The operators decided that the cost of broadcasting from 1,000 or so small "filler-in" transmitters like Woolwich wasn't justified by the benefit. This leaves a small proportion of the population unable to view them at all, and some others able to do so if they choose to spend money on changing their aerials.
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Mike O'Pray: If the two aerials are diplexed into one downlead, then that could be your problem.
Sandy Heath is traditionally Group A. Waltham is traditionally Group C/D. By "traditionally" I mean in the days of four-channel analogue.
For an explanation of aerial groups, see here:
Aerials, TV Aerial and Digital Aerial
The diplexer will allow certain channels to pass from each aerial. For example, see here:
Online TV Splitters, Amps & Diplexers sales
SDN from Waltham is on C29 which is a Group A channel and therefore won't reach your receiver if there is a diplexer. Also, Sandy Heath's SDN is now on C51 which could be filtered out in favour of the Waltham aerial.
The question is, which aerial are you using to pick up ArqA and ArqB. To find out, go to Pick TV and Yesterday and find out what channels they are on. They may both be coming from Waltham which are 56 and 57 respectively. Or for Sandy they are 52 and 48.
If you are picking up ArqA and ArqB from Waltham, then you will either have to replace the whole lot with a single wideband aerial, or just turn the Waltham aerial round to face Sandy. The suggestion latter assumes that the channel at which the diplexer splits is below C48.
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jb38 / Mike O'Pray: Surely if the aerial on Sandy is a wideband one, then it will work on its own (i.e. remove the diplexer and connect only the Sandy aerial).
However, if it is Group A (see the link I provided at 12:04AM), then it won't be suitable for receiving the COMs from Sandy on 48, 51 and 52. In which case, perhaps the solution is to swing the Waltham aerial around to Sandy (so that they are both facing the same way).
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Tuesday 15 May 2012 10:58AM
stuart smith: I don't think that you've got any chance of getting more channels until 24th October, and even then I don't think that your chances are tremendous, particularly with the loft aerial.
There re two types of broadcaster multiplex (signal): Public Service Broadcasters (PSBs) and these carry BBC, ITV1, ITV1+1, ITV2, C4, C4+1, E4, More 4, C5 and the four HD services from BBC, ITV1 and C4. The rest are Commercial broadcasters (COMs).
The transmission power of the PSBs from Caldbeck are 100kW and the COMs are currently at 15kW. The power of the COMs will go up to their full final power of 50kW on 24th October when Divis vacates those channels at its switchover. Divis is serves the eastern side of Northern Ireland.
On the basis that one of the 100kW PSBs is a bit hit and miss with your current aerial (in its current location), then I don't think that you could pick up the 15kW COMs.
I used the tool on the Megalithia website to get an idea of how your line of sight to the transmitter is affected. See the plot here:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
This assumes that your receive aerial is 10m of the ground, although the exact figure is probably not that important. What it does show is that the ground a mile away from you is around 100m above line of sight.
If you are looking at a different aerial, I would definately go with a Group A one. All Caldbeck's channels are Group A and wideband yagi aerial' gain drops off at Group A channels. See here for some traces that illustrate my point:
Gain (curves), Again
My sympathy goes out to you. You can replace your aerial (or move your aerial, e.g. to outside) now so as to get good reception of ITV1, C4, C5 etc, but you have no way of knowing whether it will be sufficient to pick up the COMs come October and you may therefore have to set too again at that time in an attempt to get them.
Alternatively, you may move your aerial outside (for example) and find that you can pick up the COMs now on an intermittant basis. You may read into that that when the power increase comes in October that the aerial will (fingers crossed) be sufficient to pull them in reliably.
I'm not an aerial installer; I'm just a technically minded person giving my thoughts and observations.