My Freeview box has no EPG, is blank on FIVE, ITV3, ITV4, ITV2+1, has no sound o
To deal with the problem you must clear the channel list completely and then rescan - if your box has it in the menus, please the 'installation menu' to do an initial scan or a reset to factory settings or First Time Installation. You MUST delete the entire existing list of channels. On most boxes this technique can be also be used:
1) unplug your Freeview box (or idTV) from the mains;
2) unplug the aerial from the Freeview box by disconnecting the cable from the 'RF in' socket;
3) wait 30 seconds;
4) plug Freeview box (or idTV) mains back in;
5) do a complete scan for channels - it will fail without the aerial. (This may be in the installation or initialization menu, and is distinct from any 'add channels option'). Once this is done your channel line up should be empty;
6) reinsert aerial by reconnecting to the 'RF in' connection;
7) do a complete scan for channels again.
The Freeview channel line-up provided by six "multiplexes" - each of which carry five or more TV channels, radio channels, text services and EPG data. In this diagram each ROW represents a multiplex. If you are still missing a whole multiplex (ie everything on the row) you may need to replace your aerial with a wideband type, purchase a larger aerial or you may have interference from a VCR, games console, Sky Digibox or similar.
Thanks for you detailed reply.
I have a compelling argument as to why my problem is NOT caused by high signal levels.
All Freeview channels carried by "Old" channel numbers 22, 23, 25, 26, 28, 30 and 35 are being received perfectly. This includes channel 30, which in London carries the Full HD channels BBC1, BBC2, ITV, Channel 4, Channel 5, CBBC and TBC (this being a narrow bandwidth H264 commerical gospel channel).
My problem is only with the low power COM7 and COM8 which radiate at 746MHz and 754MHz.
My own theory is that these much higher frequencies are attenuated more by the roof felt and the slates.
Then of course there is the matter of the trees - which change with the season.
I asked you if you could direct me to a website to give me the compass bearing to Crystal Palace.
Such a site existed a year ago - but not now, as far as I can see.
I notice that when I installed the 20 element aerial - it was ordered from CPC around 20th October 2019. With a compass. Having endured some months of BBC Four HD misery on the non-performing 10 element aerial installed may in April or May 2018, I got six months of decent reception.
Until the leaves came out on the trees??
You said in your replay that the Crystal Palace COM 7 and COM 8 signal had been boosted from 40kW to 84 and 81kW. Where did you get that from. I am wondering whether they have actually altered the radiation pattern - pointing it towards Nigel Farage perhaps, rather than rebellious Brixton?
Just to repeat my TV shows now sign of overloading on Freeview 1-105. Or 231-235.
On the other hand it shows severe lack of signal on channels 106,107,109 etc PLUS 93 PBS America+1 (which I watch a lot in the morning - or did until now).
The TV I use has a sort of signal strength indication - but this seems a bit unreliable.
Your comments about my railway viaduct problems - yes is the signal is week all sorts of things happen to the picture (chopped in half, goes green, sound screetches like bats), Currenntly this woud happen on channel 93 - PBS+1, although most of the time totally unusable.
On the other hand all the non-HD channels plus BBC1-Channel5 HD are very stable.
Over to you mate.
PS the aerial currently installed is https://cpc.farnell.com/a…1003
I do have all the previous ones, except the very first Band A on for analogue which I scrapped.
But I don't see a 10 element 1990 wideband installed for analogue channel 5 OR the Band A 10 element aerial I had to install when Freeview went HD (for me 2010), or the 10 element Band T aerial I had to install when Arqiva/OFCOM introduced the wretched COM7 and COM8. I don't see how they will help me now. You are only suggesting that because of you incorrect hypothesis about the signal being too strong.
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David Warner: "I asked you if you could direct me to a website to give me the compass bearing to Crystal Palace.
Such a site existed a year ago - but not now, as far as I can see. "
If you'd read Chris.SE's reply properly, you would have found the new location of that website :
"The bearing to CP hasn't changed, it's still 152 degrees (~SSE) and the DUK/Freeview Detailed Coverage Checker got moved to different cyberspace - not too cleverly - you had to use the boxes on Freeview | All your favourite TV shows, all in one place and all for free & scroll down and selected Detailed view, but they've recently added boxes on Freeview | All your favourite TV shows, all in one place and all for free corporate/platform-management which goes straight to Detailed View. "
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Did you use the links provided then? I'm guessing not based on your further post on another page. Unfortunately this site has messed up the link to the Platform Management page (but you had the other option), you can get to it easily by scrolling to the bottom of the Freeview Home page and clicking the link under Corporate.
Just because you have "apparently perfect reception" of other multiplexes is NOT a compelling argument that you don't have overly high signal levels. How a set front end handles too much signal depends on it's front end design, some do it well with no obvious problems, some show immediate picture or sound breakup but quite often the sensitivity is reduced and so it can become "deaf" to weaker signals. And I already explained about the Transmission Mode for the Local multiplex which is why the coverage is "better" with lower power.
You said "this local low power multiplex comes in so strongly from Crystal Palace to Brixton that you don't need an aerial to receive it". You also said "The TV I use has a sort of signal strength indication - but this seems a bit unreliable." That's something else that can happen with too much signal, I did mention that a receiver "could falsely show less than 100% signal"
You have a 20 element yagi 3 miles from CP, that IS a compelling argument that you MIGHT have too much signal even when considering the railway viaduct.
But before I comment further on experimenting, we'll mention the trees. I'm going to quote part of an article written a few years ago by Bill Wright, a very experienced TV engineer, it was in analogue days, but the principles are EXACTLY the same for digital signals.
"The customer will say that he's enjoyed perfect reception--or what he regards as perfect reception--since the days of John L. Baird.
'Those trees have always been there and they've never affected reception before', he'll declare.
The dreaded credibility gap looms up in front of you! In reality the customer has probably always had rather unreliable reception, but it's never been quite this bad. Why does it happen? Why does one channel just disappear? The cause of the problem is multipath reception through the trees. The signal takes a number of different paths through the leaves and branches. In the simplest case, if signals following two such paths arrive at the aerial more or less in phase no great harm is done. But if they chance to arrive exactly out of phase and of equal strength the result is no signal. It's never quite as clear cut as this of course. The signal may take a multitude of paths, resulting in a complex and unpredictable pattern of standing waves, or peaks and nulls, at the receiving site. Because a relatively minor change in the tree structure can completely alter this pattern, reception can be acceptable for years until a null happens to occur precisely at the aerial location. Normal movement of the trees, even on fairly still days, is enough to cause great variations in received signal strength."
So, just to complicate matters further, the FEC change to COM8 will have had the effect of improving the signal in a lot of places, often seen an increase in signal strength (that could tip your front end just over the edge) BUT this isn't only seen just when using an omni-directional receiving aerial (that's really more applicable to DAB) as TV aerials have "side-lobes", "front-to-back ratios" aren't always the best, and another transmitter with an "Interfering signal" may well be within the beam-width of the receiving aerial. So in other words reception can become better or worse, it very much depends on location and those factors mentioned.
So what next. Well you MAY have a combination of multipath and too much signal.
Assuming the aerial is in exactly the same position as it was when you had good reception of COMs 7&8 then it seems to me that spending a fiver on a variable attenuator is a small price to pay for a bit of experimenting without which you have no clue as to what is going on.
This is where I would start. See what happens to your reception and set's signal strength for all multiplexes as you increase the attenuation. Assuming either that's not the problem or only part of it, then I'd try repositioning the aerial, not just tipping it or altering the bearing, move it several inches or even feet, taking care of where any metal objects, solar panels, roof flashing etc are, and trying to ensure they are not in close proximity or line of sight. Apart from this possibly changing the received strength, it'll probably have some effect on any multipath.
If you still haven't got a satisfactory result, try one of the other aerials. CLEARLY the Group A are NOT the ones to try. So you've mentioned the 10-element and also a Log-periodic, both will have different characteristics, so experiment. RF can be a bit of a black art, it's a case of suck it and see in this sort of situation.
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