All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Jim: The Commercial (COM) services, which include ITV4, don't have as wide a reach as the Public Service Broadcaster (PSB) ones.
The COMs transmit from 81 of the largest sites (largest by viewer population) and reach 90% of the population. There are over 1,000 small "filler-in" relays which carry only PSB channels because the COMs do not wish to invest in them. These cover 8.5% of the population.
The cost to the COMs to broadcast from these other sites is about the same as what it costs them for the ones they have now. As there objective is profit from selling advertising which they show to as many viewers as possible at lowest possible cost, then it's not surprising why they don't want to broadcast from the other sites. They don't have any "Public Service" obligation.
You've said that you reside in ST13 which is a big place and doesn't give any absolute indication of which transmitter you are receiving from. Indeed, provision of a full post code doesn't either, although it might narrow down the possibilities.
I do note that it is the area of Leek and that it has one of the PSB-only relay transmitters, so I wonder if you are receiving from it, hence why you are not picking up the COMs.
For a full list of services, see here:
DMOL Post-DSO Multiplex Channel Allocations
As shown, there are three PSB multiplexes (PSB3 is the HD one) and three COMs ones.
If you are using the Leek transmitter, then in order to see if you can ever receive the COMs terrestrial channels, then you need to investigate the possibility of receiving from one of the transmitters that carries them, such as Sutton Coldfield.
If you can't, then you will have to look at some other platform to receive additional channels. Freesat is a common alternative, particularly in areas where the Freeview COMs aren't available. There are some differences between full Freeview and Freesat. For example, Dave and Yesterday are not available on Freesat and this is probably because they are on Sky's subscription service. This does, of course, require a different box.
If you provide your location, preferably in the form of post code, we may be able to assess the likelihood/degree of difficulty you may have in trying to pick up the COMs.
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Richard: For information and a source for logs, see Aerials, TV Aerial and Digital Aerial
Rugeley transmitter only carries the Public Service Broadcaster (PSB) multiplexes. For a list of the six multiplexes, see:
DMOL Post-DSO Multiplex Channel Allocations
To receive the COMs as well, you will probably have to pick-up from Sutton Coldfield. You mention a secondary television; if the primary one is terrestrial, then why not use the existing aerial for both?
Television Aerial Boosters / Amplifiers, Splitters, Diplexers & Triplexers
See the page on the mb21 Transmission Gallery for Rugeley:
mb21 - The Transmission Gallery
There is a comment on that page about an issue in the area with reflections of Sutton Coldfield's signals caused by the local power station's cooling towers. The relay itself uses a four-log array to receive from Sutton Coldfield for this reason.
Digital is more tolerable of reflections, so to what degree it will be an issue in your location, I don't know.
I'm not an aerial installer, but I understand that when you are talking such a low powered transmitter, line of sight is almost imperative.
Obviously the cooling towers aren't likely to be causing any reflections of the low powered signal from the school!
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Jack: A television which is described as HD Ready can display HD pictures, but does not have the means to receive the HD signals over the air. That means that it will require a separate HD receiver, whether this be a terrestrial one (Freeview) or a satellite one (e.g. Sky HD or Freesat HD). Click the words "HD Ready" for an explanation.
Only sets labelled as Freeview HD and/or with DVB-T2 in their specifications will receive HD as that is the standard that is used for it in this country. DVB-T is the standard used for standard definition terrestrial broadcasts, so a set capable of receiving standard and high definitions will have a DVB-T and DVB-T2 tuner in.
As for the question of getting all the Freeview channels, the UK has a two-tier terrestrial transmitter network. The biggest 81 transmitters carry the full service (they are the biggest by viewer population). There are over 1,000 small "filler-in" relays, including Newhaven, that carry only Public Service Broadcaster channels (PSBs).
The 81 full service ones carry both the PSBs and the Commercial multiplexes (COMs). This provides the COMs with coverage of 90% of the population. The cost to the Commercial broadcasters of transmitting from the 1,000 or so sites would roughly double their cost of transmission whilst only adding about 8.5% of the population to their potential viewer-bases. Because they operate on a profit making basis, by selling advertising which they show to as many viewers as possible which aquire at least possible cost, they aren't interested in transmitting from the small sites. The Commercial broadcasters have no "Public Service" obligation.
All transmitters broadcast the four HD services of BBC One HD, BBC HD, ITV1 HD and Channel 4 HD, as these are on a PSB multiplex.
For a list of services by multiplex, see here:
DMOL Post-DSO Multiplex Channel Allocations
That page shows the six multiplexes (each is a separate signal). All six are available from the 81 full service transmitters with the remaining being PSB-only.
Wideband aerials are needed in some cases because frequencies used by particular transmitters are spread out across the band and aren't all within the same portion used for the former analogue services.
Thus, in order to get the COMs, you will need to receive them from Heathfield or possibly Whitehawk Hill (adjacent to Brighton Racecourse) or Rowridge (on the Isle of Wight and is the main transmitter serving a portion of the south coast).
The predictor does not say what you "will" receive; it should be used merely as a guide. What you can receive depends on many factors and an on-site assessment can only really decide either way. Local obstructions such as buildings and trees can be an issue.
Whilst you don't have line of sight to Heathfield, owing to Beddingham Hill, it doesn't look to be too much of an issue.
I had a look on Streetview to see if there were any clues. I couldn't spot any aerials except for one on Glynn Road which is visible from your cul-de-sac. This one is pointing at Heathfield, so may give rise to the hope that you can receive from it.
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Sticks: Perhaps the poor HD mux on 29 from Stockland is why it decided to go with Honiton; i.e. the latter is the better of the two.
Whilst receiving from Honiton is a possibility, it will mean that you will then not have any of the COM services (see DMOL link I provided above).
However, as you are just less than four miles from the transmitter, I wonder if your receiver is being overwhelmed by signal and it is distorting, hence the poor quality (HD signals suffering from this before any other).
See here for an explanation and possible remedy:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
The COMs are at half power with respect to the PSBs from Stockland, so it is to be expected that if you do have too much signal that it will be one of the PSBs that will be affected.
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Jack: I take back what I said about the aerial I saw being on Heathfield. It is in fact on Rowridge, as is another on Glynn Road.
If you decide to try and receive from Rowridge, then I suggest that you use a Group A aerial and not a wideband yagi as their gain is lower on Group A channels, which is what Rowridge uses.
See here:
Rowridge Transmitter
Also, for best reception from Rowridge, have the aerial vertical rather than horizontal.
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Nick: Now that the transmitter is on full power, try turning your aerial to see if it is currently a little off-beam.
I know with my own experience with Emley Moor that the PSBs appear to be stronger. The aerial can be turned off-beam to the point where the COMs degrade but the PSBs are still strong and good quality. All six are at the same transmission power, so it must be the beam of the signal being put out that's different.
There are discrepancies between the number of people who are expected to receive PSBs+COMs as against those who will get PSBs only from transmitters that carry both at the same power:
The commercial multiplex after switchover: ArqA, ArqB and SDN | ukfree.tv - independent free digital TV advice
Like Emley Moor, Sudbury is one of those whose COMs are at the same power as PSBs. Maybe the beam of the COMs' signals aren't quite as high towards the horizon as the PSBs.
It is also worth pointing out that the higher the gain of an aerial, the narrower the angle of acceptance is, as gain is simply a trade-off of sensitivity in different directions. So the more "gain" you have facing forward, the more "loss" you have in other directions. Hence it could be more critical that it must be pointing exactly on target.
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Michael: Whether a box needs retuning when at a different location depends on whether it is the same transmitter that is being used because it is the transmitter's signals to which it tunes to that matters.
If your next door neighbour is using a different transmitter to you and you want to take your TV round to theirs, then you will have to retune.
If you are using a high power transmitter that covers a large area, you might go 100 miles to another location which receives from the same transmitter and hence won't need to retune.
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Sticks: The suggestion of trying an attenuator was to reduce the signal levels from Stockland, with a view to getting its HD watchable.
I suggest a 20dB variable one so it can be adjusted. Here is one such example (other sellers and outlets are available):
VARIABLE ATTENUATOR TV SIGNAL REDUCER 20dB 3 5 6 9 10 12 15 18 DIGITAL FREEVIEW | eBay
If you have a Group A aerial (red tip) for Stockland, then you should be aware that Honiton is Group B. See here for aerial groups:
Aerials, TV Aerial and Digital Aerial
However, group aerials don't receive nothing outside of group. You may argue that the Honiton signal is so strong due to the close proximity that it is OK, afterall, you have already picked up a strong signal from it with the aerial in opposite polarity...
See here for some gain curves which show sensitivities on different channels (these are just examples to illustrate a point):
Gain (curves), Again
You may find that even with what may be an out of group aerial for Honiton, it still picks up too much signal and needs attenuating.
As for tuning, I said to unplug the aerial at 30% to get Stockland and miss out Honiton. So if you start the scan with the aerial unplugged and plug in at 30% you should get Honiton and miss out Stockland.
Remember that the TV only stores channels it "sees" during the automatic tuning process. If you prevent it from "seeing" the ones you don't want, then it won't store them!
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Mik: The problem could be that, having carried out its scan of frequencies, the BT Vision box has decided to go with the signals from the Lyminge relay transmitter. This only carries the Public Service Broadcaster (PSB) services which are BBC, ITV1, ITV1+1, ITV2, Channel 4, Channel 4+1, E4, More 4, Channel 5 and the four HD services.
See if you can find out whether this is the case or not. I'm not familiar with the BT Vision box, but usually receivers give the UHF channel number (frequency) that they are tuned to on the signal strength screen.
BBC One should be tuned to C50 (for Dover) and not C22 (Lyminge). Similarly, ITV1 should be C51 and not C25.
If either of these are not tuned to Dover, then run the automatic tuning scan with the aerial unplugged up until 40% of the scan. This will miss out scanning of the frequencies used by the unwanted transmitter.
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Sunday 1 July 2012 1:01PM
KMJ,Derby: I'm thinking from the point of view of frequency planning. The plans keep getting changed and thereby force some to take action by changing their aerials in order to continue receiving TV.
The fact that there will be further generation mobile services in the future is surely a given. So where might they go? When might GSM be turned off, and therefore the frequencies thrown free for later generation services?
Am I right in understanding that the reason that the 800MHz frequencies are needed because 3G only uses the 2100 band and that this doesn't provide as good a service due to higher frequencies not travelling as well (walls attenuating signals etc)?