All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Peter McMahon: Lots of advice and products at www.aerialsandtv.com
Wideband yagi are less sensitive at lower (Group A) frequencies. See 
Gain (curves), Again
If you're going for Divis and require a high-gain aerial, probably best to get a Group A on rather than a wideband. This is the advice given by ATV.
One thing I will say is that prior to switchover, Mux C is on channel 48 and this is the only one that is outside Group A. After switchover, Divis will return to being a Group A transmitter. lisa: There has been no retune events for Rouncefall.
I wondered if there might be any connection to your change in reception and switchover events that happened last night.
Midhurst switched last night but it did not use the same channels as Rouncefall before or after switchover. Chris: There are quite a few areas of Wales where the Commercial (COM) channels such as Dave will never reach. Due to the terrain, there are many small transmitters that the Commercial operators aren't bothered with.
Merthyr is one such example; it is a Freeview Light transmitter, only carrying the Public Service Broadcaster (PSB) channels.
See 
Freeview multiplexes | ukfree.tv - independent free digital TV advice for a list of all the multiplexes. The PSBs are BBCA, BBCB and D3&4. The COMs are SDN, ArqA and ArqB.
ITV4 is COM and I am not aware that there is a Welsh version. Are you referring to S4C? If so, in Wales S4C is on logical channel number (LCN) number 4 and Channel 4 is on LCN8.
If you provide a full post code, a more accurate prediction of the likely possibilities can be made. Aberdare transmitter is a full Freeview transmitter (it carries PSBs and COMs). It also requires aerials to be vertical.
Looking at your neighbours' aerials will also yield clues.
For Merthyr Tydfil transmitter, your aerial should be vertical. 
Phil: A look at the Digital UK Tradeview predictor for your post code (click the link next to your posting) is interesting.
For all multiplexes from Midhurst, it regards 100% of the post code area "served" (on its criteria). However, C61 (D3&4) is 96% "served" and 100% "marginal", so too is BBC B (HD services) on C58. The key here is not the absolute values, but the relate difference of these two multiplexes.
This could perhaps be a suggestion that there is another transmitter whose signals might be detrimental to reception of these multiplexes from Midhurst at this location.
In October this year, D3&4 is due to move to C56, and that too has the same 96% served prediction.
I've looked at the transmitters which use C61 and I've not come to any definate conclusion. Mendip uses C61 and C58. It also uses C56 at the same power as 61 and 58. JIM: Could you receive any Freeview before switchover?
If your aerial is pointing at Brighton Central, then you will only receive BBC channels; the rest will come next Wednesday.
All the aerials I can see in your road on Google Streetview are on Brighton Central and it is on the top of Theobald House. Aerials should be horizontal for it. george austin: If your combi does not have Freeview built in (that is it is analogue only; previously you receive only the four or five channels), then it will need a separate Freeview box to work after switchover.
This creates its own issues when programming by timer. You would need to set the timer on combi and that on the Freeview box (or leave the Freeview box turned on). george austin: The poor picture you have on BBC channels could be as a result of your receiver tuning to a transmitter other than the one to which your aerial faces.
You have said that your aerial is on the roof, but have not said which transmitter or which direction it is pointing. I shall assume that it is directed at Whitehawk Hill as that is where all the aerials point in your road on Google Streetview.
For Whitehawk, aerials are vertical and it is located near to East Brighton Golf Club and East Brighton Park. You are near to the Brighton Central transmitter which is a "filler-in" for those that can't receive Whitehawk. There is also the possibility that you could be picking up the main Rowridge transmitter (Isle-of-Wight).
To find out which you have, go to the signal strength screen whilst on BBC One and it should tell you what UHF channel it is coming in on. If it's 24, then you are picking up Rowridge, if it's 41 then you are picking up Brighton Central and if it's 60, then it's Whitehawk.
If you are picking up Rowridge, then run the automatic tuning scan with the aerial unplugged up until 50%. If it's Brighton Central, then that's a bit more tricky. Try 50% and if you still have issues, post back and I will offer a further suggestion. lgb2100: This tells us that one is tuned to one transmitter and the other is tuned to the other.
As a guess, you have Emley Moor and Bilsdale which give Yorkshire and Tyne Tees respectively. As you haven't given your location or direction of the aerial which is common to both (or indeed which transmitter it is facing), then there isn't really much else I can say. lgb2100: I wouldn't have thought that you could pick up Emley Moor in South Shields!
Perhaps it is or was a mistake on the EPG. trevor: The Commercial multiplexes are at low power and restricted in the general direction of Guildford due to being co-channel with some of its services. The Public Service multiplexes are not. Jon Stanley: Assuming that you are receiving from Mendip, then wait until 28th March when Arqiva B multiplex which carries Sky Sports will go to full power. ATOMS: The Commercial broadcasters do not wish to spend money on transmitting from some 1000 or so small relay sites such as Haslemere.
Digital UK Tradeview doesn't rate Midhurst at your location at all, not even "poor". I think that the fact that there is a hill in that direction means that you're not going to get it.
The next best transmitter, which is shown as "good" is Crystal Palace, but unfortunately the Commercial (COM) channels (which Haslemere doesn't transmit) are co-channel.
The only other suggested possibility is Hannington, but its COMs are shown as "poor" and their transmission power is half of its power for the Public Service channels (which are "variable"). Tony: With a more exact location I could perhaps be more specific.
But taking the post code LL11 5UN and inputting it in the Digital UK Tradeview predictor gives:
Postcode Checker - Trade View
There are a number of transmitters found. The only Welsh one is Moel y Parc, but Sutton Coldfield comes up tops.
Unfortunately, BBC A (standard definition services of BBC One, BBC Two etc) and BBC B (HD services) are co-channel (same frequency) with those of Commercial services from Sutton Coldfield.
This means that you will only be able to pick up ITV Wales and S4C until 2013 when they too will be co-channel with Sutton Coldfield. This is unless there is somewhere your aerial can be mounted where the signal from Sutton Coldfield can be blocked such as on one side of your house (not sure how effective this might be).
As I say, with a more accurate location I might be able to be more specific, but based on what I found, the Sutton Coldfield would appear to be the spanner in the works. (GU273RW) Dave Williams: I think that Winter Hill is your only possibility of receiving Granada/North West TV. If you are looking at DIYing, then I recommend that you look at ATV Sheffield's website. It's full of lots of information and they sell stuff mail order.
This page is what they recommend for Winter Hill: Winter Hill Transmitter (LL115UN) geoff: If you are picking up BBC A (BBC One, BBC Two etc) multiplex from Rowridge on C24, then you could well pick up the other higher power multiplexes when they come on air next week.
Fortunately Rowridge's services are at low frequencies and Whitehawk's at high ones, so just run the automatic tuning scan with the aerial unplugged up until 50% to avoid the possibility of picking up Rowridge. dannar: Perhaps it might be worthtaking some photographs.
The first thing to do is talk to your neighbour about it because it will obviously involve him or her. Nicholas Willmott: The question should surely be, does Ofcom have the Statutory powers to require the operators to broadcast from all relay sites (assuming that there are channels available)?
The other thing is that if the current Commercial operators were to have broadcast from all sites (or as many as there are spare channels for), then it's likely that the channels in the 30s, cleared for the future three licences (COM7, COM8 and COM9) would have had to be used for them. This would mean that there would be no auction and therefore no revenue from the sale of the COM7, 8 and 9 licences for wherever such monies go.
Out of interest, where does the revenue from Commercial licences go, the Chancellor? Nicky: I think that you have quite a good chance of some result if you can position with a good view in the direction of the transmitter.
It's not possible to give an absolute "yes" or "no" answer; more a likelihood of success.
With 20 miles clear line of sight to Belmont, unless there are local obstructions, then you shouldn't have a problem.
Your chances of success are greater at the side of the house that faces the transmitter, providing that there is, for example, another house there. Upstairs is also better than downstairs.
I have one of these Labgear aerials that I use where a fixed aerial isn't available:
Set Top Aerial Labgear | eBay
As I say, Belmont is your best option which is north east from you. You may even be able to see it on a clear day and see the red lights on it at night. Neil: Gauging your likelihood of success requires a more precise location, preferably in the form of post code. This is particularly so in your area as with the hills and valleys, what can and can't be picked up can vary house by house.
You say that when analogue was switched off, you lost many Freeview channels. This implies that you did receive some before. If you received some before switchover, then you must have been picking them up from a main station such as Wenvoe. The relay transmitter at Abercynon did not carry Freeview before switchover and only carries Public Service channels now.
If you could pick up the weaker pre-switchover Freeview signals from Wenvoe (or another transmitter that operated pre-switchover, then you should not have an issue now, being as the signals are stronger.
So if you picked up Freeview before, what did you use? Robert: The reason you have duplicated channels is because your receiver has picked up the new full power BBC services from Rowridge which are on C24.
Rowridge uses low channels/frequencies and Whitehawk high ones, so if you run the automatic tuning scan with the aerial unplugged for the first 50% it will miss out Rowridge and pick up Whitehawk. Mike W: It is possible that the BBC One you are watching (which is breaking up) is not from Midhurst but from another transmitter.
The best thing is to confirm that it is from Midhurst. If you go to the signal strength screen whilst on BBC One it will hopefully give you the UHF channel number that it is tuned to. In this case it should be 55.
If it's anything else, then let us know what it is so as to suggest a possible solution. Wendy Townsend: What is the model name and number of the recorder?
When you connect the recorder box into the aerial lead, do you loose all channels on the TV? Grant Buckley: Looking at the location and the fact that your aerial is, one assumes, on the top of the six storey block, you should not have any issues with signal strength.
Where a communal aerial system is provided, then the signal should be the appropriate level when it comes out of the wall socket. If it's not, then it is the operator's responsibility. The operator is probably the landlord.
However, the first thing to check is that the your receiver is tuned to the signals from the transmitter to which the aerial faces. The height of the aerial makes it very likely to be receptive to signals from other (which the aerial does not face).
Which programme channels show low signal strength and drop-out?
Also, for each of the following, go to the signal strength screen and let us know which UHF channel it is tuned to. Receivers usually give this information, although not always.
BBC One (probably channel 24 or 47)
ITV1 (probably channel 21 or 44)
BBC One HD (if applicable) (probably channel 27 or 41)
ITV3 (probably 42 or 51)
Pick TV (probably 45 or 52)
Yesterday (probably 39 or 48). Grant Buckley: Yesterday will probably be 39 or 48; let us know which. Chris: ITV4 isn't the same as Channel 4. I think a little potted history lesson is necessary.
In 1955, "ITV" started up, which is a group of regional operators such as Granada, Meridian, Yorkshire etc. Over the years, the regional operators have been bought and now those in England and Wales are all owned by the same company, ITV Plc. Today it uses the "ITV1" wallpaper for its network of regional stations. I'll come on to why the "1" has been added.
In 1982, the fourth television service was launched in the UK. For everywhere except Wales, it was Channel 4. Wales got its own fourth service, S4C.
The introduction of the digital system ("Freeview") means that more channels can be broadcast. This has lead to the BBC, ITV Plc, Channel 4 and others introducing other channels.
The BBC started up BBC Three and BBC Four, ITV Plc has ITV2, ITV3 and ITV4 and Channel 4 has E4, More 4, 4Music and Film4. The "1" on ITV has been introduced due to the other three ITV Plc services being in operation.
Because the Freeview system can carry more channels, Channel 4 can now be broadcast Wales, as well as S4C. Because button number 4 is used in Wales by S4C, Channel 4 is on button 8 in Wales.
The transmitter called "Aberdare" is on the hill to the east of Cwmbach. See here for a map of the location:
Bing Maps - Driving Directions, Traffic and Road Conditions
And here for photographs:
mb21 - The Transmission Gallery D
ITV HDSaturday 17 March 2012 12:56PM
Beryl Gray: Yesterday is one of the channels that is not available on Freesat, but is available on the full Freeview service. As you are in an area served by full Freeview now, then you will be after switchover.
Yesterday is not available on analogue and has never been. Terrestrial analogue consists of BBC One, BBC Two, ITV and Channel 4. Channel 5 is available on analogue with limited coverage.
As you TV is likely to have Freeview built in, or you have a separate Freeview box if it doesn't, then you would be best advised to retain it and the terrestrial aerial as a back-up should the satellite services be unavailable and also so you can view channels that aren't available on Freesat. S Williams: Try running the automatic tuning scan with the aerial unplugged up until 63%. You may have to manually add C48 for ITV3 etc. Grant Buckley: Your reply has confirmed that all channels are tuned correctly to the same transmitter, Emley Moor.
As you have found, digital broadcasts carry a number of services as part of the same signal. That is you get a basket of programme channels on one frequency known as a multiplex. The six I listed above are each part of a different multiplex.
When did this problem begin?
Have you tried changing the aerial lead from the wall to the TV? Is it short? Stuart O.: As a guess, I would say that the significance of 24th October is that it is the date the the whole of Ireland switches to digital TV. I wonder, therefore, whether "reactive power" means that the power might be reduced should the signal travel further than normal and interfere with other services on channel 48.
The mention of 12.5kW is perhaps the figure that was quoted by official sources such as Ofcom at the time it was written. As I say, if you refer to the latest Ofcom document, it says 10kW for the COMs, so this would appear to be the current value.
Perhaps one of the pros could shed more light on this and whether my guess might be right. Paul: The current "digital switchover" is for terrestrial television only. It has nothing to do with radio and nothing to do with DAB.
The design of some receivers leaves a lot to be desired. This is not specifically confined to the "cheapo" sets.
There will always be instances where signals from adjacent transmitters overlap. Some boxes just go with the first one they find.
Transmitters do broadcast their "Network" name, but not all receivers display it. However, most receivers display the UHF channel that is being received and this information is usually given on the signal strength screen.
In some cases where incorrect transmitter(s) are being picked up, it's possible to remove the aerial lead for part of the scan to get it to do what you want it to do.
It is possible to do this with the caveat that you will have to manually add a couple as they are mixed in with those of Heathfield.
Midhurst's channels are 55, 61, 58 (HD), 62, 59, 50
Heathfield's are 29 to 54 now and 41 to 52 after its DSO.
So, if your receiver shows UHF channel numbers when it's scanning, start it off with the lead unplugged and connect it after it's scanned 54 to avoid Heathfield. You will then need to manually add 50 (Yesterday etc) and probably 55 (BBC standard definition services).
If your receiver doesn't give channel numbers, but only a percentage, then the scan is likely to be from channels 21 to 69, so plug in around 71%. Then manually add 50 and 55 as explained above.
Whilst this may be clumbersome, it might be more attractive than letting it put Midhurst in the 800s and you having to swap each one. Peter: Some receivers, having performed the automatic tuning scan, will ask the user to choose the "Network" or "Region". This is in fact selection of which transmitter to go with. It is therefore important to ensure that the correct one is selected and that the default should not necessarily be chosen (which could be the first one in alphabetically). Simon Miller: It should improve come switchover.
Tunbridge Wells is traditionally a "Group B" transmitter. That means it uses frequencies in Group B which is roughly the middle third of the band used for television.
Consequently, Group B aerials are likely to have been fitted. They are aerials that are much more sensitive around Group B frequencies.
Unfortunately, some of the pre-switchover digital channels are outside of Group B, them being higher. This means that your aerial (if it's Group B) won't "hear" these as well. The affected multiplexes are Mux 1, Mux 2 and Mux D; see the top of the page for the services that these carry.
After switchover, all multiplexes will use Group B frequencies. So I would not replace the aerial because the current one should work OK from 13th June. steve: The likely answer is never as the Commercial broadcasters do not wish to invest in transmitters at 1000 or so small sites like Dallington Park. They achieve around 90% coverage of the population from about 80 sites nationwide. They were invited to increase their coverage but declined. The cost of broadcasting from the relay sites would roughly double their costs of transmission.
They work on a commercial basis where they generate revenue from advertisers. The objective is therefore to get as many people to view the adverts as possible at the lowest possible price.
See here for a fuller explanation:
Will there ever be more services on the Freeview Light transmitters? | ukfree.tv - independent free digital TV advice Frank Sanjana: I'm assuming that you're receiving from Hannington. If so, then the Commercial channels will remain on low power until 4th April for SDN (which carries ITV3 and others) and until 18th April for ArqA and ArqB which carry Pick TV, Yesterday, Dave, Film4, Sky News and others.
The missing channels you identify are all on ArqB multiplex and you need to try manually tuning to C47 for them.
If you have a signal booster, you should try removing it.
You may be able to get all channels to work, or perhaps at least get Sky News and Food (ArqA) to be more solid by putting an attenuator on line with your aerial lead. I am referring to a device such as this: www.ebay.co.uk/itm/VARIABLE-ATTENUATOR-TV-SIGNAL-REDUCER-20dB-3-5-6-9-10-12-15-18-DIGITAL-FREEVIEW-/370552240392
The issue could be that there are now high power digital signals BBC and ITV1 etc when there wasn't before. These could be acting to desensitise your receiver and in so doing it doesn't "see" the lower power channels you're having problems with.
The attenuator will reduce the level of all signals. A variable one such as the example I've given will allow the level of reduction of signals to be varied so as to see if a happy medium where all will work can be arrived at.
So basically the hope is that the level of the high power signals can be reduced sufficiently (to increase the sensitivity of the receiver) *and* that the degree of attentuation does not reduce the level of the weaker signals too much so as to not be receivable.
There is therefore no guarantee that a balance can be struck. Sarah: On the basis of what JimF has said, to increase your chances, your radio probably needs to be on the side of the house facing Exeter with the clearest possible view in that direction. Try taking it upstairs on that side of the building and see what sort of signal strength you get on each multiplex.
St Thomas broadcasts BBC National (12B), Digital One (that's the commercial national multiplex and it's on 11D) and South East Devon (11C). Sarah: Having taken it from the shop all tuned in, then the worst thing you can do is rescan.
Once tuned, the radio "knows" what channels are available and will receive them when sufficient signal is available to it.
Rescanning wipes its memory so it no longer "knows" what's available and you then have to get this list of what it "knows" back by repeated re-scans until you have them all.
Where you have the radio in a location where it is tuned to a particular station but where there is insufficient signal to hear the station, then retuning cannot possibly have a positive impact in that it will not enable you to hear the station. The only outcome it can have is a negative one (i.e. you loose the station in question from the list). pete: Is your aerial directed at the Steyning transmitter (your aerial will be vertical) or is it on Midhurst (aerial will be horizontal)?
If your aerial is on Midhurst, then you shouldn't be tuned to Steyning and its existance will not improve your reception from Midhurst.
It is worth confirming that BBC and ITV1 are tuned to the transmitter to which the aerial faces.
From Midhurst, BBC is on C55 and ITV1 on C61.
From Steyning, BBC is on C59 and ITV1 on C50.
Therefore, when it is scanning, Midhurst is the first BBC signal (of the two transmitters) and Steyning is the first ITV1 signal. I wonder, therefore, if this could have resulted in your main ITV1 signal being tuned to Steyning when in fact it should be Midhurst.
You should be able to confirm either way by viewing the signal strength screen whilst on each channel; most receivers give this information. Derek Green: Can you not get a more reliable signal from the Poole relay? Derek Green: The vertical element of the COMs will only be introduced on 18th April when they change channels and when their ERP is increased.
The vertical element of the PSBs' signals has been introduced at switchover. Kim V: Confirm that the jerky BBC channels are coming in on channel 24 and not 46 which is Winterborne Stickland or even 61 which is Mendip. Dino: In circumstances such as yours, you would be best advised not to retune because the only possible outcome is that (most likely) you loose the programme channels from your receiver or you get them back. Crucially, the act of retuning cannot have any affect on getting them back, therefore they would have come back anyway if they are back after retuning.
The act of retuning is therefore like shooting oneself in the foot. Only where there is reason to retune, such as a change of channel should retune be carried out.
The only way you are going to get it back is to repeatedly manual tune to channel 31 until it comes back, whereas had it been left, you could simply have select CITV to see if it was back. martin: For Whitehawk Hill, all channels post-switchover are "in group", that is they are in Group C/D. This was the case before switchover, except for analogue Channel 5 which was on channel 35. So a wideband aerial is not necessary after switchover.
You will not pick up HD signals yet because they aren't being broadcast!
High definition services become available at the second stage of switchover, which for Whitehawk is this Wednesday. charlo: BBC Local Radio is on DAB multiplexes that are operated by commercial companies. Thus, the areas that they are available is dictated by the areas that commercial broadcasters wish to serve.
The national BBC multiplex could never carry different stations in different areas because DAB does not allow it. It is a single service nationwide and is carried on the same frequency in all areas (a "Single Frequency Network"). 
19:51
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