All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
D. Brooks: Now that Emley Moor has switched over, can you receive its signals with a set-top aerial? Could you tune your digital receivers to it until Bilsdale's switchover?
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Nick: Where does it recommend a C/D aerial for Tacolneston?
It is Group C/D for PSBs, and Group E for PSBs+COMs.
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Nick: C60- is still above C59 and C59+ for that matter!
If there is a signal on C60-, then there can't be one on C60 or C59+ or, I believe C59. There could be on C59- though. Each signal has a specific bandwidth; that is the "width" of frequency it uses.
As an example, take Caldbeck. Transmitters that use C30 have a negative offset, so it is always C30-.
Caldbeck uses C22- C23- C24- C25- C26- C27- C28- C29- C30-
So because C30 has a negative offset, then C29 must do so as well, and so on and so forth.
Had there been no C28-, for example, then C27 and below wouldn't have had negative offsets.
The reason for nine channels is because Caldbeck transmits English and Scottish regional variants.
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Nick, Jason: There are many transmitters and only a relatively few channels. Had there only been two transmitters Sudbury and Tacolneston then no doubt they would have had all channels within each one's Group.
The main plan was to have PSBs in the same Group as the former four-channel analogue. Crucially this was so as to ensure that existing aerials would work; in some cases replacement aerials would be needed to receive the COMs and in others the COMs would be unavailable.
C61 to C68 which were formerly used for analogue are to be cleared. Some C/D transmitters have given up use of these channels at switchover and others will do so over in the next year or so. These frequencies are being set aside for 4G mobile operators. What it does mean is that there are now less C/D channels available than before.
Also, C31 to C37 have been ringfenced and are not used after switchover. Consequently available Group A channels are now C21 to C30.
Belmont is traditionally Group A. Its PSBs and COM4 are Group A, but the other two COMs are on C53 and C60. Similarly, Sandy Heath is also formerly Group A, with its PSBs being in that Group, but COMs being on C48, C51 and C52. Also consider Waltham which has five muxes in C/D but COM4 on a lowly C29.
These transmitters overlap, so the channels are:
21 Sandy Heath PSB3
22 Belmont PSB1
24 Sandy Heath PSB2
25 Belmont PSB2
27 Sandy Heath PSB1
28 Belmont PSB3
29 Waltham COM4
30 Belmont COM4
42 Tacolneston COM4
45 Tacolneston COM5
48 Sandy Heath COM6
50 Tacolneston COM6
51 Sandy Heath COM4
52 Sandy Heath COM5
53 Belmont COM5
54 Waltham PSB2
55 Tacolneston PSB1
56 Waltham COM5
57 Waltham COM6
58 Waltham PSB3
59 Tacolneston PSB2
60 Belmont COM6
61 Waltham PSB1
62 Tacolneston PSB3
Hopefully you get the idea. Think of the other high power transmitters that overlap these; Sutton Coldfield, Sudbury, Emley Moor.....
Then there are PSB relays within the coverage of each that requires channels within the Group of former analogue ones.
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Adrian Durrant: Good to hear that you have success. It's great when a plan comes together!
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philip j Thomas: Run the automatic tuning scan and unplug the aerial when it gets to 61% (or past UHF channel 50 if it gives channel numbers during the scan).
Receivers usually give the UHF channel number that they are tuned to and this will allow you to identify which transmitter you are receiving.
Newhaven BBC One is on C50 and ITV1 is C43. HD services are on C40.
Whitehawk's BBC One is on C60 and ITV1 is on C53. HD services are on C51.
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philip j Thomas: The UHF channel number that is tuned is usually given on the signal strength screen.
Newhaven doesn't carry the Commercial (COM) multiplexes, but as your TV has tuned to Whitehawk now, it may be possible to manually tune to it for the Commercials and Newhaven for Public Service (PSB) channels.
Whitehawk's COMs:
- COM4 | ITV3 etc | C57
- COM5 | Pick TV etc | C56
- COM6 | Yesterday etc | C48
Due to the point I advised you to unplug the aerial, you may have COM6 but not COM4 and COM5, and these will need manually tuning.
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Nick: I'm not sure why it says "To receive Freeview from the Tacolneston transmitter you will require an aerial of group C/D positioned horizontally."
Looking at the channel allocations prior to switchover, all analogue and digital were C/D at that time. Perhaps this message has not been updated since then. Only 42 and 45 are out of C/D Group though.
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Tuesday 24 July 2012 5:10PM
Trevor Rhodes: Short answer: Have your aerial changed from horizontal to vertical.
Long answer: The Poole relay does not carry the Commercial (COM) multiplexes; only the Public Service Broadcaster (PSB) ones, so you would be worse off. Indeed, it is COM5 you are having issues with, and you may be susceptible to poor reception of COM4 and COM6 as well due to the clash with Stockland Hill.
For services and which multiplex they are carried on, see:
DTG :: DTT Services by Multiplex
After switchover, digital signals from Rowridge are broadcast horizontally and vertically. The horizontal signals are there there for compatibility with existing aerials.
The PSBs (BBC, ITV1, ITV2, C4 etc) are at a power of 200kW horizontally and vertically, whereas the COMs are 50kW horizontally and 200kW vertically. The COMs are lower power horizontally because the three channels (frequencies) so that they can be used by other transmitters (in closer proximity than what the PSBs' channels are re-used).
In your case, you could be suffering from interference from Stockland Hill as its COMs use the same three channels. It is horizontally polarised only, so changing your aerial to vertical polarisation should help "rejection" of the unwanted signals.