All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Andy: If channels are breaking up then retuning is only ever likely to remove them from the tuner's memory. This assumes that they were tuned to the correct transmitter in the first place.
This is because the tuner remembers the frequencies used by each channel and as they haven't changed, any retune is simply attempting to tune in to the same frequencies. Unless the receiver has "forgotten" the channels (highly unlikely), one is a glutton for punishment or it is found that the receiver is tuned to the wrong channels, retuning should not be attempted.
I gather that, like Elliott, you are receiving from Stockland Hill rather than the Teignmouth transmitter, which is the page you've posted on. The Teignmouth transmitter only carries PSB channels (see the link I provided to Elliott to find out which these are), so reception of COMs (which include Sky News) would be expected to be intermittant or non-existant due to the signal being received off-beam of the aerial.
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Andy Hearn: Co-channel interference from France maybe. In which case the high-power transmitters in France (those that are likely to cause interference) are horizontally polarised. Rowridge has a vertical component, of which the COMs are stronger, so vertical polarisation will help reduce likelihood of co-channel interference from France as well as better COM reception.
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GLENN: Best to switch your aerial to vertical polarisation as the COM channels (those that you're having difficulty with) are 50kW horizontally and 200kW vertically. The Public Service channels are 200kW horizontally and 200kW vertically.
This will also help reduce the likelihood of interference from transmitters in France, which are horizontally polarised.
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David Sutton: Unless you've checked, then it could be that the French stations that you are receiving are not on the same channels/frequencies as the desired ones from Rowridge, and therefore aren't the ones that are compromising local reception. However, it does suggest that signals are carrying further than they normally do and so that could be the cause of the difficulty you are having.
It is possible that it is another transmitter that is interfering with the signals from Rowridge at your location. This doesn't mean that either will be receivable as there may be no overall "winner". Also, unlike with analogue, digital receivers will not start to show the picture carried on the offending signal (if/when it gets strong enough) because they are "looking" for the tuned signals.
So even if the interfering signals come in strong enough to wipe out reception from Rowridge *and* be watchable, your set would still show "no signal", *had* you left it tuned to Rowridge.
As suggested to Glenn, have your aerial switched for vertical polarisation. Never say never, but the transmitters in France that are likely to interfere are horizontally polarised.
Rowridge broadcasts horizontally and vertically, with the Commercial channels being on lower power using the former polarity and are equal to that of the Public Service channels on the latter.
This means that there are potentially two benefits to vertical polarisation.
You should not need to replace your aerial, unless it is defective of course. For some transmitters aerials used for former analogue need replacing to get the full Freeview service. With Rowridge the only thing that is needed is to switch to vertical polarisation.
If you do decide to get another aerial, then don't get a wideband. These are the types that DIY shops sell. These aren't the best for Rowridge. For more information (whether because you wish to install a new aerial or just wish to be informed before calling in a professional), see:
Rowridge Transmitter
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B. O'Neill: There has been engineering work taking place in preparation for switchover. We do not know what this was/is, but it is a possibility that it was something that may affect reception, particularly in areas where the current low-power signals are marginal (i.e. "only just" good enough).
It is possible that whilst the other channels are perhaps "only just" above the threshold required to produce a picture, that C33 is now "only just" below the threshold.
There is no such thing as a "digital aerial". Aerials work based on the frequencies of the signals that they are installed to receive.
In the days of four-channel analogue it was commonplace for aerials to be fitted that are most sensitive to the group of channels/frequencies used by the desired transmitter.
For Divis this is "Group A" which is the first or lowest third of frequencies used for TV. Before switchover all digital channels are within Group A except Mux C which is up on C48. In some cases (at some locations), the lower power pre-switchover digital signals may not be strong enough to be received (or "heard") by aerials that are sufficient for analogue. Where this is the case, replacement with a more sensitive aerial may yield reception of those digital channels. However, it is expected for Divis that, generally speaking, (Group A) aerials installed for analogue will work for digital after switchover on 24th October. This is because all of Divis' channels will be in Group A. The stronger signals should also mean that aerials that are more sensitive (higher gain) that were installed pre-switchover aren't necessary.
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Phil B: No, unfortunately Newton is likely to remain a Public Service-only transmitter.
The Commercial broadcasters (those that aren't going to transmit from Newton), cover 90% of the population by 81 of the largest transmitters (largest by viewer population). For them to broadcast from the remain 1,000+ small sites like Newton would give them another 8.5% of the population whilst roughly doubling their cost of transmission. As they're in it for profit only (no Public Service obligations), then don't wish to do this.
So unless you can receive from a full-service transmitter, you'll be stuck with "Lite". Pontop Pike and Fenham are the two closest full-service transmitters.
"If" you do decide to delve down the route of reception from Fenham, see ATV's site for lots of information:
Digital TV Transmitters
In particular, Fenham is all Group A after switchover, so if you get a yagi aerial, don't get a wideband one. Indeed, as suggested by ATV, a Group K aerial won't be needed after switchover, so get a Group A one. (See ATV's site for information on aerial groups.).
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Norman Langridge: The COM channels (22, 25 and 28 from Rowridge) do not have as extensive coverage as the Public Service Broadcaster (PSB) ones. Over 1,000 small relay transmitters don't carry them as they are PSB-only. In some cases viewers will need to replace their aerials because the COM channels are broadcast from their chosen transmitter, but outside of the Group of their aerial (that is on UHF channels outside of those that their aerial is most sensitive).
Some transmitters that do carry the COMs radiate them at lower power than the PSBs and this is so that the COM channels can be "re-used" by another transmitter in closer proximity than would otherwise be possible (without the power restriction).
This is the reason for the lower power horizontal COMs signals from Rowridge. These three are used by two neighbouring main (high-power) transmitters: Stockland Hill to the west and Crystal Palace to the north east. These are horizontally polarised only.
The nearest that the three Rowridge PSB channels are used by main transmitters are Redruth to the west, Ridge Hill to the north west and Sandy Heath to the north east. These are further away than the two mentioned at the end of the previous paragraph.
Rowridge is unique in that it is the only main transmitter that broadcasts mixed polarities.
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dave carter: The Commercial (COM) channels do not have as extensive a coverage as the Public Service (PSB) ones. The former is available to about 90% of the population and the latter covers around 98.5% of the population. Perhaps, whilst you're on holiday you are in the 8.5% who can't get the COM channels.
Over 1,000 "filler-in" relays don't carry the COMs which means that those who can't receive from an alternative full-service transmitter must do without. Some of the 81 transmitters that do carry the COMs do so with a lower transmission power which means that some viewers on the fringes won't get them.
There are quite a few coastal locations that, because the ground goes down towards the sea, are served by relays and these are PSB-only. The same is true of valleys.
Without knowing where in St Austell you are, it is difficult to get any idea of what the chances of getting a full service is. However, St Austell does have its own relay which suggests that there are parts (or all) that can't receive directly from a main station such as Redruth.
For the St Austell transmitter your aerial should be vertically polarised and if you are tuned to it, BBC One will be on C62 and ITV1 will be on C59. HD channels are on C56. (Click on the hyperlink "St Austell" above to see its location.)
You may have to be on higher ground to receive from Redruth. If your TV is tuned to Redruth, then BBC One will be on C44, ITV1 on C41, HD on C47. Your aerial should be horizontally polarised. If you find that you are tuned to Redruth, then have a go at manually tuning the COM channels:
COM4 (ITV3)=C48
COM5 (Pick TV)=C52
COM6 (Yesterday)=C51
Redruth is one of the transmitters that radiates the COMs at lower power than the PSBs.
I have been general here because I don't know exactly where you are (even then it might not be a rough prediction).
For a list of which are PSBs and which are COMs, see (those with a bullet in the "E"/England column apply):
DTG :: DTT Services by Multiplex
You might be interested in this page for touring aerials:
TV Aerials for Boats and Caravans
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dave carter: The signal strength screen usually gives the UHF channel that the receiver is tuned to.
Even if your TV has automatically tuned to the St Austell transmitter doesn't necessarily mean that reception from Redruth is out. You may have to manually tune to Redruth (if available), or, when you run the automatic tuning, pull the aerial out at 70% so as to miss out scanning of channels 56, 59 and 62 (those of St Austell). I emphasise that this doesn't necessarily mean that you will be able to pick up Redruth.
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Sunday 9 September 2012 12:01PM
Fred Erridge: It is also the case that Hastings' PSBs share channels with the COMs of Rowridge. Before switchover these two transmitter did not share any (high-power) channels. Also, Rowridge is now broadcasting vertically and is in roughly the opposite direction to Hastings, so perhaps your aerial could be picking up a bit of interference from the back.
For these reasons, generally speaking, it is probably best to receive from Heathfield in Eastbourne where this and Hastings are possible.