All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Jon: It's not possible to say with total and utter certainty, but I think that technically you are pushing your luck to receive anything other than the PSB (Public Service) channels, whether that be from West Burton relay or direct from Bilsdale.
From Bilsdale the COM channels are at half power to the PSBs. They also use a less robust mode so that they can cram in more services (more shopping channels).
So if you are struggling to get Bilsdale's PSBs, then you ain't gonna get its COMs.
That said, contract aerials are cheap crap:
Aerials, TV Aerial and Digital Aerial
Have you tried manually tuning in the other multiplexes? If you do, once you enter the UHF channel number, but before you press the button to scan, wait and see whether it gives any indication as to quality and strength.
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Looking at the terrain plot, the difficulty is Penhill:
Terrain between ( m a.g.l.) and (antenna m a.g.l.) - Optimising UK DTT Freeview and Radio aerial location
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Chris : Not via terrestrial television.
Marlborough isn't likely to ever broadcast any of the Commercial (COM) multiplexes which Sky Sports (subscription) and other free-to-air services. There appear, looking at Digital UK Postcode Checker, that there are no other transmitters that might provide you with the full complement of channels.
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M S Hahn: My thoughts on this:
For lots of information about aerials, see ATV's site: A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial.
1. The modulated analogue output of the Sky box provides a picture of inferior quality to that of the scart or HDMI. It also gives only mono sound. With that thinking, perhaps you should consider resiting the Sky box by extending the feeds from the dish. If you use a scart connection, then you should ensure that the output is switched to RGB (as opposed to composite video which is usually default). I haven't ever used a Sky box, but a scart output's default is usually composite video because some TVs don't have RGB capability.
2. Can't help you with making wife more understanding...
3. Stockland Hill uses Group A channels exclusively. Therefore, if you use a yagi aerial it should be a Group A type as wideband yagis are inferior on lower (Group A) channels and manufacturers will always quote the highest gain which is on higher channels. If you use a log periodic aerial then these have a flatter response curve and are wideband, so these are fine. See:
A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial. gaincurves.html
You have the right idea, amplifying the signal before the subsequent loss caused by the cable.
If your "twin arm fringe aerial" is a log periodic phased-array then be aware that this will have a narrower acceptance angle than a single aerial.
An aerial's gain is simply at the expense of more "loss" in other directions. So a higher gain aerial (if it were used for transmission) sends out a narrower beam. Obviously the degree to which it is sensitive when receiving is narrower on the same principle; perhaps appreciating how it acts when sending out signals is easier to get one's head around than when receiving.
With this in mind, when you have a "beam" from the transmitter that you are trying to receive, then a narrower acceptance angle might be OK because you can focus on it - but it will be more tricky to align because it's obviously more critical.
I have looked back at your previous postings and noted that Digital UK Postcode Checker "thinks" that 100% of your postcode unit are served by all Stockland's channels. This doesn't take account of trees that might shadow the signals, but nonetheless gives a general indication that your general area is good.
However, I have seen your postings which give the OS grid reference of your location which, I see, even the Google Streetview car didn't go to!
You say that you are lower down than the other properties in your postcode. So this makes me think that your difficulty is simply because of this. "If" you could elevate your house or barn, then you would have an excellent signal.
So you are trying to pick up what signal is coming over the brow. Think of this (the signal) as being like car headlights coming towards you (which you can't directly see) shining over the summit of a slope.
With digital TV quality is the important factor which is essentially digits intact and not corrupted. If your narrow-beam aerial happens to be aimed at a signal which has poor quality, then your picture will be poor irrespective of how much you amplify it. A wider acceptance angle will "take in" a wider range of signal (including that of the narrow angle aerial array), and so the average quality across that angle may be far better (that is the hope) than the smaller bit your narrower aerial could pick up and so the result will be better quality, albeit lower amplitude for which you are using an amplifier to boost.
I simply making the point that a higher gain aerial isn't always best. Yours may work, or you may find that a single log aerial will give you better quality.
I am not a professional installer and hold no qualifications in the subject; I've just taken in the principles of the topic.
One other thought: the Digital UK Postcode Checker also suggests that reception from Mendip might be excellent as well. Would this be a better bet, and resort to Sky for regional programming?
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Jon: Digital reception is pretty much an "all or nothing" system. So either the picture is "perfect" or "nothing".
I believe that the PSBs are radiated from a single antenna array.
The reason for the differences in reception is due to other variables. Different frequencies get reflected and refracted to differing degrees due to adjacent objects. Aerials, broadcasting and receiving, spread and are sensitive to frequencies to differing degrees.
The gain of an aerial is simply at the expense of greater "loss" in other directions. The less gain you have the less directional it is.
As you've seen, yagi aerials' gain curves slope downwards on lower channels. The size of the reflector on the rear is important as the lower the frequency the longer the wavelength and hence the longer the reflector needed to achieve the same level of "reflection" and hence directivity. Hence, because the reflector is the same length, the gain must be less. (Other factors may also play a part in causing this slope; I'm just considering the effects of the reflector.)
Bill Wright, a great authority on aerials, talks about "short reflector syndrome":
http://www.wrightsaerials….pdf
If you are looking at new aerial, then have a look at ATV's site for information: A.T.V (Aerials And Television) TV Aerial, DAB Aerial, FM Aerial.
If you try to achieve the full complement of channels from Bilsdale, then a Group K aerial is the best single aerial to use. Or, alternatively, a Group A aerial diplexed with a Group B one with a diplexer that "splits" at C38.
Unfortunately, "if" you find that you can receive COM channels from Bilsdale with a Gruop B aerial you will be unable to combine this with an aerial on the West Relay (for PSBs) because it also uses interleaved Group B channels. Therefore, in such circumstances you would have to receive Bilsdale's PSBs, although, as I've said, the COMs are inferior to the PSBs, so if the former are possible, then common sense suggests that the latter will be.
If you were to purchase only a Group B aerial for reception of Bilsdale's COMs and it didn't work, then you may be able to use it for reception of West Runton's PSBs. If you find that you can pull in the COMs, then you could add a Group A aerial.
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Jon: If you are conversant with going up on the roof safely, then you may find that reorientating the aerial(s) (and switching them to vertical) will work on the relay. Perhaps this will be until you get a more suitable aerial, but will provide reception until then.
It might be worth replacing the cable with double-screened coax typically used for satellite installations where the higher frequencies necessitate it:
Satellite, Television, FM, DAB, Aerial, Coaxial Cable, Plugs, Sockets, Connectors & Leads
If you do sucessfully receive from Bilsdale, then a mast-head amp to boost the signals might be necessary.
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Jon: Of course, a Group K aerial would also be suitable for the local relay. So if you tried it on Bilsdale and it won't pull in the COMs, then you could switch it to the relay instead.
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Jon: I'm not a professional and don't have any formal qualifications in this subject.
See also my posting to M S Hahn on aerials' acceptance angles which are narrower the higher the gain:
Freeview retune day - how was it for you? | About UK Free TV | ukfree.tv - 10 years of independent, free digital TV advice
Therefore, there is a trade off and higher gain might not be what you want as you don;t have a "beam" to point your aerial at because the terrain does not allow. You are trying to receive what is being refracted over the brow.
A professional on here has commented that a lower gain log periodic aerial used in conjunction with an amplifier may yield better results.
As I say, I'm not a professional, so it might be worth seeing what others on here say before buying an aerial.
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Sid,: See the comments at the end of the Pontop Pike page. Quite a number of people have experienced this on the logical channel numbers which are all carried on the "SDN" (COM4) multiplex. Out of interest, what is the make and model of your receiver? According to reports, this is generally affecting Panasonics.
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Another report of the same issue here:
QVC | ukfree.tv - 10 years of independent, free digital TV advice
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Wednesday 9 January 2013 7:20PM
And another report stating issues at two addresses:
ITV 3 | ukfree.tv - 10 years of independent, free digital TV advice