All posts by Chris.SE
Below are all of Chris.SE's postings, with the most recent are at the bottom of the page.
Michael Murphy:
The "trick" is not to retune when you have no signal or badly pixellated pictures, it'll clear the correct tuning and sometimes "mis-tune" you to signals that are only briefly there.
The only time a retune is needed these days is when broadcasters (on the COM muxes normally) go swapping/changing their channels and you usually get a pop-up to tell you.
The only recent exception was the BBCB HD mux recently when they finally got Regional News on BBC ONE HD. Similar may be needed when ITV get theirs sorted.
You are only predicted to get variable reception from Whitehawk Hill which is why it's more vulnerable to co-channel interference when weather conditions are such, as you say, more common in summer, but we are seeing more of it at various times of year!
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Valerie Butt:
To be clear, we don't send anything out, this is an independent technical help-site. BUT to answer your question -
TV Channel (LCN)52 is one of 6 channels carried on Local Multiplexes which are only transmitted from a limited number of main transmitters (and often beamed towards a large centre of population). Dover doesn't have one.
See Channel listings for Industry Professionals | Freeview for which TV Channels are carried on which multiplex.
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Peter Goodhugh:
The Salisbury transmitter is on Harnham Hill, but there are several transmitters that could be received in your postcode.
Which local news do you get? South Today/Meridian or West/West Country?
And which way is your aerial pointing - compass bearing 186 degrees - fractionally W of due S, with its rods (or squashed Xs) vertical, or is it 276 degrees - fractionally N of due W. If it's the former, that's Salisbury, the latter is Mendip (West). But you might also get Hannington, roughly ENE with rods horizontal.
Depending on where you are within your postcode - lower numbers not doing as well, predictions show you signal could be good to variable, but a lot will depend on aerial height and any very local obstructions (buildings, tree etc).
There are no currently reported faults at the Salisbury transmitter, however, bearing in mind your predicted signal might be variable, recent weather conditions meant that you may have had interference,, with signals from distant transmitters.
If you retuned at all when you had no signal or badly pixellated pictures (never advised), very often this can just clear your previous correct tuning, however it's unusual for such interference to affect all multiplexes as it's usually frequency dependent.
Do you still have no signal?
If you still have no signal, check that everything is correctly plugged in behind your TV and the aerial socket, and check that the aerial is still pointing correctly and the downlead isn't flapping in the wind.
If you didn't retune before and still have no signal, and your aerial looks ok, you may have a fault on your aerial system - do you have any aerial amplifier/splitter?
Check in your TV Tuning section that you are correctly tuned to Salisbury's UHF channels (as listed at the top of the page).
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Paul Cook:
Trying to resolve difficult issues like this remotely is never easy. As this is an independent technical help-site, we don't have any history of your installation so we'll need some more details shortly.
Belmont was listed last week for Planned Engineering with "Possible effect on TV reception week commencing 01/05/2023" "Pixelation or flickering on some or all channels". It's not on the current list this week but it's possible work hasn't been completed, we know the lists have been inaccurate on some occasions. So this may have been the cause of your problems last week. In addition to which, there was some brief variable weather related tropospheric ducting which can result in interfering signals from distant transmitters in Europe or the UK.
That all said, your predicted reception is not the best being that you are 76km from Belmont albeit it's your most likely main transmitter, but note, your location could receive signals from 3 other main transmitters. Whilst predictions aren't always 100% they suggest that reception from Belmont of the PSB multiplexes should be more reliable than the COM multiplexes.
(See Channel listings for Industry Professionals | Freeview for which TV channels are carried on which multiplexes. PSBs are BBC A, BBC B, D3&4. COMs are SDN, ArqA & ArqB.)
Reception in a specific location can of course be affected by local surroundings, potential obstructions on the line -of-sight, trees, buildings etc. as well as aerial position. As you've noticed you are getting slightly different results form each aerial, but there may also be other reasons for this. It may be helpful if you can say which other TV channels especially you get problems with apart from BBC (SD or HD) ones.
It does concern me that you mention you have 4 filters on your main aerial. You don't mention the second aerial. You do however seem to have a lot of mobile masts nearby especially in the general direction of Belmont!! You mention "Freeview" engineers - were these sent by Restore TV or were these local aerial installers you called?
You mention amplifiers, can you advise if these are masthead or internal, and make & model if internal - also do any have variable gain control? Please detail each aerial installation separately and if possible do you know the make and model of the aerials, and/or roughly when they were installed?
I assume they are both pointing at Belmont, compass bearing 327 degrees ~almost NNW.
As you may have retuned at some point (never advised if you have no signal or pixellated pictures if already correctly tuned), can you check in each TV Tuning section that you are correctly tuned to Belmont's UHF channels - C22, C25, C28, C30, C23, & C26 (as listed at the very top of this page).
Also for each set, in the TV Tuning section can you list the Signal Strength & Quality (or BER/Error) figures for each multiplex.
Sorry that's a lot of information, but as much of it as you can provide will be helpful, do one set/aerial at a time if you like. Oh out of curiosity is Yorkshire your "preferred region" for local news or would you have a preference for Anglia or Central (East)?
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Wendy McLellan:
Hi there. It sounds like you might have 2 or 3 separate problems there.
The Findon Relay is currently listed for Planned Engineering with possible "Pixelation or flickering on some or all channels" - as mentioned in the post immediately before your first.
This could well have been compounded by recent weather conditions (tropospheric ducting) that cause signals from more distant transmitter in Europe or the UK to give interference to your wanted signals. This won't often affect all multiplexes, so not all TV channels are necessarily affected and not everyone is always affected. This interference can be quite variable lasting seconds, minutes or longer. It should not be affecting your area at this time.
You might also be suffering interference from a new/updated mobile phone mast, perhaps more so with the HD TV channels. Have you had a postcard from Restore TV UK at all?
Unfortunately your postcode is not predicted to get very good signals from Findon, are you sure your aerial is pointing that way - compass bearing 86 degrees that's virtually due E with its rods (or squashed Xs) vertical. Despite a nearby hill you are predicted to get much better signals from Rowridge (compass bearing 245 degrees ~WSW with its rods horizontal - you'll also get more channels as Findon doesn't have the COM multiplexes.
See Channel listings for Industry Professionals | Freeview for which TV channels are carried on which multiplexes.
The interference I mentioned above could also disrupt some mobile phone signals if you aren't in a strong location for the network you are using, but that ought to be better now.
It might also be worth you checking in your TV Tuning section that you are still correctly tuned to Findon if your aerial points that way. because if you retuned at all when you had badly pixellated pictures or no signal (never recommended as it usually clears correct tuning) you then have to repeat a retune when the signals are normal and you may have to try several times as you won't know when that is!
Findon's UHF channels are listed at the very top of this page.
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Chris Perkins:
Hannington hasn't been listed for Planned Engineering in recent weeks and I can't find any reports of recent faults listed. There has been some quite variable "tropospheric ducting" with recent weather conditions and this can cause interference from distant transmitters in the UK or Europe which can disrupt your reception. That can last for seconds, minutes or longer, not all multiplexes are necessarily affected and not everyone will get problems, it can be very frequency and location dependant.
One of the difficulties of your location is that you can receive signals from several transmitters, but not all will provide reliable reception of all multiplexes.
Hannington is predicted to give good reception for most multiplexes for most of your postcode, but predictions are just that and specific reception will be affected by any immediate local buildings , trees etc which can't be taken into account in a general prediction.
Your location unfortunately has a large forest on the line of sight to Hannington and this could have a large effect in the wrong atmospheric and weather conditions, so that when you have to retune as you needed to for the recent HD changes it's possible that you may inadvertently get tuned to the incorrect transmitter for some multiplexes because of conditions at the time , which of course will change and give unreliable reception.
Check in your TV Tuning Section that you are correctly tuned to Hannington's UHF Channels -
These are C45, C42, C39, C40, C43, C46 & possibly Local multiplexes on C32 or C34 but the Locals are not predicted in your postcode.
That's in the multiplex order BBCA/PSB1, D3&4/PSB2, BBCB HD/PSB3, SDN/COM4, ArqA/COM5, ArqB/COM6 & Locals Basingstoke or Reading.
You might even get the London Local multiplex on C35 off the back of your aerial!
See Channel listings for Industry Professionals | Freeview for which TV channels are carried on which multiplexes.
If you continue to have problems, post back with more detail and specific channels.
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nick:
Hi. I( suspect you are misreading/reading the wrong thing in what I said. According to the Freeview checker, your predicted reception of COM6 is better than COMs 4 & 5 which is why it's a bit surprising that you experience COM6 on C37 getting disrupted first.
Reception will vary across the postcode because of the changes in local(ish) terrain and it seems lower street numbers in your postcode fair slightly better according to the predictions!
No doubt the frequency planners will have had a bit of a nightmare in trying to decide on the best channels to use for specific multiplexes on various transmitters when considering co-channel interference, taking account of the obvious line-of-sight issues but also less common propagation due to temperature inversion and tropospheric ducting.
Whilst most of it is done by well established computer predictions, no doubt there'll have to have been some manual fine tweaking ....... and there are some instances were it is far from ideal which is of course why it wasn't done at the outset if that's what you meant by tight groups.
If you meant use of adjacent channels at a given transmitter, that's not a problem with digital, but analogue had to be spaced apart often 3 or 4 channels.
You would have struggled a bit with the Sudbury COM muxes at DSO as these were technically above Group B, a Group E aerial really being needed. And with the 700MHz Clearance those COMs moved right down the band where then a Group K was required.
It was because it was known that these types of changes were likely to be needed in the future that back in the day a Wideband aerial was recommended, or a Group T when the 800MHz band was cleared, and now after 700MHz Clearance, as there's nothing above C48, a Group K is in effect the new wideband and in fact desirable to minimise the likelihood of mobile interference if you could be near a mobile mast using 700MHz.
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Richard Sutton:
I'm afraid that your assumptions and conclusions are flawed.
There's been no Planned Engineering listed for Ridge Hill in recent weeks and there's been no listed faults that I've found in this period. Therefore there would be no reason why the D3&4 multiplex would not have been transmitted correctly.
Apart from which, if there had been an unreported fault, lots more people would be complaining AND you've had this issue for a very lengthy period.
Also as previously mentioned, all 6 multiplexes are transmitted from the same antenna, albeit the PSBs are 20kW and the COMs 10kW, this makes little difference to coverage until you start getting into fringe areas.
Your location has line-of-sight to the Ridge Hill transmitter, so anything further away from you that you cannot see will have a negligible effect on received signals.
You haven't commented whether you have tweaked the amp/splitter gain down as suggested to try and optimise the Quality across the multiplexes.
If you have simply put everything back as it was, then I expect little to change over time.
You also seem to have ignored checking for any possible sources of interference that may be especially affecting C24.
Does the amp/splitter have an unused VHF input at all? If so, try putting a shorting coax plug in it to see whether that has any effect.
Assuming at the end of the day, interference is not the cause, as I previously explained, trees can cause multipath reflections which can affect a (very) narrow band of frequencies and may only cause an issue at certain distances away. So the combination of the distance of the tree from your aerial and it's physical nature might result in primarily C24 being affected.
As for alternatives, did you look at the possible line-of-sight issues for Sutton Coldfield, Malvern or Lark Stoke from your aerial location? Any large trees in the way?
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Sunday 7 May 2023 2:30PM
Michael Murphy:
Recent weather conditions have caused some Tropospheric ducting/temperature inversion which can result in interfering signals from distant transmitters being received, which is what you may have experienced and in your case most likely from across the channel.
Such conditions have affected different parts of the UK at different times but may not be currently affecting your area. Such conditions are frequency dependent so not all multiplexes are affected, nor necessarily will all viewers in a particular location.
If you retuned when your signals were disrupted (never advised) this can just result in clearing the correct tuning and some times you end up tuned to an unstable distant signal that promptly disappears.
Try a MANUAL retune of your UHF channel C30 rather than a full retune which might affect the other multiplexes if there are still similar conditions present. You may have to try several times as you won't necessarily know when the signals on C30 are normal.