All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
M Rowland: You do not appear to have line of sight with the top of the Ridge Hill mast. The area in or around Westhope Hill is in the way with the slope being treelined.
The pixelation could be caused by damp in the woods. Does it happen more during dark?
See this page for a trace between your and the transmitter:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
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Shirley: Sudbury would seem the most likely transmitter at your father's location and looking at Streetview, I can't see a house that doesn't have an aerial on this transmitter. Sudbury is 30 degrees which is between north and north east.
The most common issue with Sudbury is that a different aerial "may" be needed to receive Commercial multiplexes/signals. Has your father had a new aerial?
Try and tune ITV3 in manually if the TV has such a facility. From Sudbury it is on UHF channel 58. Depending on the design of the receiver, it may indicate signal strength when you do this. This may give a clue as to whether there is a low signal which isn't great enough to give a picture.
Presumably you attempted a retune on 27th June. Can Pick TV (number 11) be picked up now? And can Yesterday (number 12) be picked up? If not, then the cause may be the same as with ITV3 - an aerial installed in the days of four-channel analogue.
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Nick: Negative offset means that the signal is centred 200kHz lower than the "centre" of the channel. A positive offset is 200kHz above the centre of the channel.
For example, C60 is centred on 786.0MHz, C60- is 785.8MHz and C60+ is 786.2MHz.
In all but a handful of cases, PSBs are on channels within the former four-channel analogue Groups for each transmitter. Where possible, COMs are also in Group, but there are now a number of high power transmitters that have COMs outside of their native Groups.
Sudbury's three PSBs are in Group B and its COMs are in C/D.
Tacolneston's PSBs are Group C/D and its COMs are Group B.
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Joe Griffiths: Which channels are breaking up? Have you confirmed that your receiver is tuned to Wenvoe for all channels?
The Van Terrace transmitter one mile away is co-channel with Wenvoe's COMs, although it is vertically polarised and only 2W.
If your Mynydd Machen aerial is Group A (red tip), then it isn't suitable for Wenvoe, which is exclusively Group B. See:
Aerials, TV Aerial and Digital Aerial
If it is a wideband aerial, then a Group B one of similar size will give better gain.
Wenvoe's COMs are half-power to its PSBs. The COMs also use a less robust transmission mode. These two factors "could" mean that the outcome is that they are unavailable, even if the PSBs are.
At present you only get PSB channels. The COMs are restricted to main stations and high power relays.
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Paul H: Waltham (assuming this is the transmitter you are using) has five channels in Group C/D and one in Group A (C29 which carries ITV3 etc).
If your aerial is a C/D one (green tip) rather than a wideband one, then this could perhaps explain why it might be suggested that it be replaced.
See the bit at the top of the page under the heading "Groups". A more in-depth look is here: Aerials, TV Aerial and Digital Aerial
It is important to appreciate that aerials don't receive nothing outside of group, but that sensitivities drop off. For some example gain curves that illustrate this point, see Gain (curves), Again
You say that the current aerial works OK for all Freeview channels. If it is a C/D aerial, then it would appear that it is sufficiently sensitive on C29 at your location.
I raise this point not to sway you in any way if it is a C/D aerial, but just to make you aware. You may decide that as it is sufficiently sensitive, to have it put back up again. Or you may decide that "good practice" is to replace the C/D aerial with a wideband one.
Another possibility "may" be to install an aerial in the loft. You could perhaps do it yourself, although obviously there is no guarantee that you will get good reception in the loft.
If you are receiving from Waltham and are looking for some advice, see Waltham TV Transmitter
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Norman: The likely answer is "never".
The Commercial multiplexes which carry ITV3 and ITV4, as well as others like Film4 and Dave do not have as wide a reach as the Public Service multiplexes. The Commercial ones operate solely to generate profit and as such broadcast from 81 of the largest transmitters (largest by viewer population) which gives them a coverage of 90% of the population. To transmit from the 1,000 or so small "filler-in" relay sites like Linnet Valley would roughly double their cost of transmission whilst only adding 8.5% of the population to their potential viewer bases.
The Digital UK predictor suggests that you might be able to receive the full service from Tacolneston or Sudbury. I looked down your road on Streetview and can see a few aerials on these main transmitters.
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Jim Charters: Perhaps your aerial is too sensitive for the location and supplying an OTT signal:
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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lindsey: In your general area the signals from Rowridge come in quite strong. Bring up the signal strength screen whilst on BBC One and see if it is tuned to C24 for Rowridge or C60 for Whitehawk. There is perhaps an outside chance that it could be on C50 which is Newhaven and is a little off-beam from Whitehawk from your location.
If it is tuned to Rowridge, then the solution is simple; all of Rowridge's channels are low frequency and Whitehawk's are high, so have the aerial lead unplugged for the first 30% of the scan (or until it gets past C35 if it gives channel numbers as it scans them). There is a big gap between the two, so there is a big margin.
If it is tuned to Newhaven, then that will be more tricky. If the receiver has manual tuning, then I would keep the aerial out for a bit longer to miss out Newhaven, knowing that some of Whitehawk's will need manually adding. In this case, keep the aerial out to 61%. Then manually tune Whitehawk's C48 which carries Yesterday, 4seven and others. HD services are on C51 and ITV1, C4 etc are on C53.
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piglet: Prior to switchover, the low power Freeview signals, and maybe analogue Channel 5 were too low a power to be useable at your location. Thus, even "if" the four analogue channels could be received from Whitehawk, there would be nothing to gain over the choice offered by Patcham which was probably a much better signal anyway.
Post-switchover, the equivalent transmission power of Whitehawk is twice that of the former four-channel analogue.
The difficulty is the high-ground that is in the way:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
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Tuesday 17 July 2012 11:18PM
Bob: If you need any parts or information on doing the job yourself, then you might like to take a look at www.aerialsandtv.com