All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
brian: Of course, Sudbury is in the same general direction, so those using it (in Southend) may well not realise and not need to adjust their aerials.
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With transmitters changing channels all the time (due to the 800MHz clearance), would it be possible to show those that will use a particular channel in the future?
At the present time there are two maps:
1. That of before switchover with the former analogue and pre-DSO digital. Switchover is done and dusted and retained purely for historical reference. I see no reason to remove it.
2. The after-switchover map which is now constantly changing and isn't so much an "immediately after switchover" representation, but one of "now" (I assume).
As well as having a map of each channel at the current time, it would be useful to have and one which shows current transmitters plus those which will, at some point, utilise the channel as well as those which will cease use of the channel. Those that are due to use channels and give them up in the future could be coloured differently or have some other variation made to their symbol.
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Keith: I'm not a professional so write purely as an interested technically-minded anorak.
With digital reception, the strength of the signal (as it enters the receiver) needs to be above a particular threshold, over which it will show a picture (providing that the signal is of good quality). Increasing the strength will provide no benefit to the quality of the picture.
With the signal above an upper threshold the receiver can become overwhelmed. This is like turning up the volume on a hifi to a level where the quality has gone because the sound is distorted due to the speakers being unable to cope.
So putting more attenuation in doesn't risk pushing the strength down too far.
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You say it is a dual-tuner machine. Does the second tuner only start up when recording and, if so, is possible to temporarily disable this feature so that it operates with only one tuner? If the single tuner functions normally then this suggests that the issue isn't recording but the presence of the second functioning tuner which is resulting in poor reception.
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FRANK: Rowridge broadcasts horizontally and vertically, and has been doing so for all channels since 18th April 2012.
The Commercial (COM) channels aren't as strong horizontally, and hence switching to vertical polarisation (where all channels are the same power) may cure poor reception of the COMs.
However, the lower power horizontally polarised COMs aren't on "low" power by any means, them being 50kW each which is more powerful than some main stations.
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Keith: I'm not sure that it is necessarily the tuner being insensitive; it could be the other way around, it being sensitive to a ropey signal (probably caused by reflections) that the others are OK with. This is purely my unqualified thought - the way in which digital signal works means that reflections are OK but I wonder to what degree. Indeed, there are a few signal frequency networks in operation now.
You can get variable attenuators or perhaps used in conjunction with a 6dB one (or greater).
The aerial you have referred to looks to be the thing. The photo is that of an Antiference LP20FHV:
Log Periodic UHF Aerials | Antiference
The one from ATV is a Blake and its elements are flat, rather than round. I'm not sure if that makes them more rugged, and perhaps, more able to withstand big birds.
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brian: In which case, the new transmitter will probably be particularly of use to those whose aerials point south to one of the BBC South East/ITV Meridian transmitters.
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Mr Andrews: Knowledge of the TV's make and model number would allow us to determine whether it is equiped with a Freeview tuner, or whether it will require a separate box.
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Matt: It is the case that there is now a two-tier terrestrial television transmitter network. About 98.5% of the population can receive terrestrial television with about 8.5% of those only receiving PSB channels.
Refer to this page for a list of Freeview services by multiplex (mux):
DTG :: DTT Services by Multiplex
Each mux is a single signal which occupies the same space as a single former analogue service.
The PSB network has been designed such that it will be available everywhere that the former four analogue channels were. The COM network fits but doesn't provide as good a coverage.
Refer to this page which the last graph shows the (then) 80 full-Freeview transmitters with projected figures for the number of homes that will receive PSB+COM and PSB-only. Whilst, undoubtedly, the figures are estimates, they nonetheless give a general indication that the COM signals are, to some degree, inferior to the PSBs.
The outcome you have could be as a result of this. Is it the COMs that are always iffy?
From what you describe, the PSBs are fine.
Try manually tuning the COMs but, having gone to the manual tune screen, enter/select the UHF channel number but don't press the button to scan straight away. See whether it gives any indication as to the strength and quality of the signal. Once you have the reading, then scan.
The COM channels from Mendip are:
- COM4 (ITV3) C48
- COM5 (Pick TV) C56
- COM6 (Film4) 52
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David Cook: Have you confirmed that you are indeed receiving the signals from Pontop Pike and not Bilsdale?
Bilsdale is a possibility, particularly if your receiver goes with the first signals it finds; Pontop Pike uses higher channels and are thus found later on in the scan.
Receivers usually give the tuned UHF channel on signal strength screens. Check the following:
PSB1 | BBC One | P=C58 | B=C26 | F=C27
PSB2 | ITV1 | P=C54 | B=C29 | F=C24
PSB3 | BBC One HD | P=C49 | B=C23 | F=C21
COM4 | ITV3 | P=C50 | B=C43 | F=C25
COM5 | Pick TV | P=C59 | B=C46 | F=C22
COM6 | Film4 | P=C55 | B=C40 | F=C28
P=Pontop Pike, B=Bilsdale and F=Fenham
For example, bring up the signal strength screen and it should be tuned to 58 for Pontop Pike, or could be 26 if it's Bilsdale or 27 for Fenham.
If you have either Fenham or Bilsdale tuned in, run the automatic tuning scan with the aerial unplugged until 53% to miss out scanning of their channels.
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Monday 7 January 2013 11:23AM
brian: Looking at the photos of the DTT panels at Rouncefall, I would say that they radiate southwards which suggests that it is intended to serve Southend-on-Sea and surroundings:
mb21 - The Transmission Gallery