All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
BillNick: On the face of it, unless the area is known for signal issues such as because there is a building in the way, then too high a signal level does appear to be a likely possibility. Generally speaking, Crystal Palace aerials used for former analogue should be fine.
See:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - 10 years of independent, free digital TV advice
If the high-gain aerial is a wideband one, then it won't be so "high" gain on the channels used by Crystal Palace. This is because the gain of an aerial varies across the range of frequencies/channels and for yagi types (which it is likely to be) the gain is always lower on lower channels.
See:
Crystal Palace Transmitter
Crystal Palace Transmitter #WrongAerialForCrystalPalace
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Paul Lister: The reason may be because you still have a Group A aerial which was installed in the days of four-channel analogue and which, crucially, isn't as sensitive at the higher frequencies used by Film4 and some other channels. It may be something that is liveable and which doesn't necessitate replacement.
An aerial isn't bothered whether it's analogue or digital - it is the frequency that it is used at that matters. In the days of analogue, for The Wrekin Group A aerials would have been installed, Group A being the bottom third of the band of frequencies used for TV. So a Group A aerial is more sensitive on those frequencies (UHF channels) and drops off outside. BBC, ITV1, C4 and C5 are still on Group A channels.
Film4 from The Wrekin is higher up (on a higher frequency) in the middle third, hence your aerial may not pick it up as well and this may explain why the automatic tuning scan hasn't picked it up on occasions.
Had this been an analogue signal, then the picture would probably have been grainy (i.e. poorer picture). However, digital is an all or nothing system with little inbetween. So providing that you can receive the signal with good quality (no breakup in the picture), then if it is weaker than the others, it isn't an issue.
The reason I draw this distinction is because strength isn't so much an issue with digital. There is a lower threshold over which you need to get for your receiver to work. Once you are far enough over it, then the picture should be fine (assuming good quality).
If your receiver has a manual tune function, then you should manually scan UHF channel (frequency) 47 for Film4.
Once you have it stored, if it continues to be available, then I would leave it as it is.
Some receivers have in-built boosters (which can be used on particular channels) and you may be able to use this to increase the strength of Film4.
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David: Waltham is curently undergoing engineering works which, according to posts made on this website, is causing reception issues for some fringe viewers. I suggest that you wait until these are complete until you adjust your aerial. You may also wish to retain the Sutton Coldfield aerial as a backup.
For aerial information on Waltham, see:
Waltham TV Transmitter
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BillNick: You could try the suggestion by KMJ,Derby. Or it could be too high signal strength, in which case you need an attenuator.
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JUNE: The answer depends on whether you receive RT etc from:
1. a Saorview transmitter in the Republic, or;
2. one of the three transmitters in the North which carry the NI Mux. This only carries RT One, RT Two and TG4.
Knowledge of your location would allow us to work out which of the above may be available.
Number 2 is intended to cover the areas that number 1 doesn't reach. In some areas both will be available.
For number 2 a Freeview HD receiver will definately be required (even though pictures are broadcast in standard definition).
For number 1 a Freeview HD receiver will definately work, although some standard definition receivers are found to work.
If you previously received RT in analogue, then this must have been from a transmitter in the Republic and therefore number 1 may apply subject to installing a suitable receiver (i.e. the current RT aerial may be fine).
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Paul Lister: No, it's not a volcano. The green area is not that which is at risk of succuming to lava.
If you receive Film4 reliably, then you can probably leave it as it is. You may have to manually tune when you do an automatic retune again, but so long as it is present (once added manually), then there will be no improvement in its picture with a new aerial.
If you are considering replacing the aerial yourself, or sending someone you know into the loft, then see this page for information on an aerial:
The Wrekin
I think, certainly in the first instance, there is no real need to replace the cabling. Just fit another aerial.
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BillNick: I suggest that you fit an attenuator to reduce the signal level. For example, type f attenuator into eBay for attenuators with f-connectors that will fit onto your splitter.
I'm not sure what level you might need. A variable one will allow adjustment.
If the wideband aerial, which isn't as effective for Crystal Palace as on higher channels, is providing too high a signal level, then there is no real need to replace it with a Group A aerial.
With digital reception there is a lower threshold over which the signal level must be in order to show a picture (assuming good quality signal). Increasing the level doesn't make the picture quality better. For this reason, don't try to get the strength as near 100% as possible.
There is also a top threshold for the level over which it is likely to over whelm the tuner. This can produce what you've described: the signal level and quality dropping sometimes jumping up and down.
The point is that once you've got a signal that is too high, the quality is likely to go. It is a bit like turning the sound up on a hifi above that which the speakers can work at; the sound becomes hideously distorted (poor quality sound).
Of course there are slight variations that occur such as due to the weather and you don't want them to push it OTT, as perhaps could have happened with BBC this morning.
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BillNick: The window is big so it's not critical.
Signal strength scales vary by receiver, but say you get a good signal with it set to 75% strength on the channels you have, then try manually adding the missing ones.
Once you have each one tuned, then don't rescan if you find one poor quality as the issue must lie elsewhere.
DC power-pass is required where an amplifier (mast-head amp) is being used at the aerial where the power supply is fitted behind the TV set. The DC voltage to supply the amp is carried up the aerial cable and thus if the attenuator were fitted inbetween the two, it would need to be the power-pass variety.
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Monday 3 December 2012 1:37PM
Mike Potter: If you have your aerial is directed to the Langholm transmitter, then try manually tuning to UHF channel 57 for BBC.