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Interference
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Like alot of other people I get the occasional blocking and pixilation.
I am using double screened cable. If I earth the outer screen will this improve things or is this not a good idea?
I am using double screened cable. If I earth the outer screen will this improve things or is this not a good idea?
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One of the many wonders of digital terrestrial television:D
I live only a couple of miles from the Crystal Palace Transmitter.
You will normally find that that the channels affected are from the same Mux, which seems in this area to be Mux D.
Ian
I would avoid doing that AT ALL COSTS! Mains earth is there to carry any high voltage leakages into the ground, in the event of an appliance fault. You wouldn't want to feed a high voltage current into the tuning circuits of your DTT receiver!!
Now I think for my area it's mux 2 thats causing it. I don't believe it to be anything electrical since practically everything else is off in my flat (and electrical disturbances are typically broadband, affecting all channels, not just a couple).
Sigh...looks like it's back to analogue for me unless I can find a fix.
Just an idea which would tie in with the fact that you're having problems with one MUX, at night time, which have only started recently. Welcome to the forums, BTW.
Its now all okay. Greg told us all last night:
http://www.bbc.co.uk/pressoffice/speeches/stories/dyke_londonbusinessschool.shtml
So don't worry. You won't get the problems caused by interference anymore :rolleyes:
I can only dream of a "Freeview" world where the bus didn't affect the picture. Shame as I live right on the corner of two roads (one which is busy 24/7). There must be at least 5 different bus routes and, during the day, a bus going past every 5-10 minutes. That's not to mention all the vans and lorries that go by as there's an industrial estate just down the road.
Thank God for satellite. One or two problems a year as opposed to one or two a minute!
What is the signal strength of that MUX???
My ITV MUX signal strength was below par as it was on Ch68 and the old aerial could not hack it - new aerial and d/s cable and sig strength up with the best of them.
Perfectly correct Skip, entirely my experience of "Freeview". Dyke appears to be speaking from the part of his anatomy where the sun don't shine.
Interference invariably gets in through the cables and wall plates and the way to minimise that is:-
Use double-screened cable from aerial to Freeview box with no intermediate connections. If you *must* use a wall plate, use a screened one. Make sure that the cable run is as far away from all electrical wiring as is reasonably practical. In some cases it may help to run it through steel conduit (suitably grounded outside via a copper stake in the earth).
Make sure the signal at the aerial is *more* than needed. That way you can fit an attenuator at the input to the Freeview box. This has two effects. It brings the signal down to the level required and it also attenuates any interference picked up by the cable.
You can get a high signal in two ways - either use a higher gain aerial than required (preferred method) or, if the signal can't be improved that way, add a masthead amplifier. In either case don't overdo it. 6dB should be fine.
Sam
Not sure of the signal strength, but it's one of those nasty 64QAM MUX's which are more prone to interference, according to the FAQ
The problem is I'm using a shared aerial, so the interference could be coming from any of my neighbours in my flat complex. Don't know how I'm going to sort that out, can't exactly go banging on doors to tell people to shut off their noisy fridges and heaters...
Well I could do all that at my new place in the hope of getting a useable and stable TV picture, but there's no point. I looked at the price for all of that and what I'd get for my money and it was just as cheap to get (multi) satellite. I knew that both required roughly the same amount of work and I knew that satellite would give me rock steady pictures 99.9% of the time.
At the end of the day though, it's not good enough that people should have to go to this amount of effort to receive digital terrestrial TV when they already have aerials that do a bloody good job with analogue. I think it's a huge step backwards that people that do have crystal clear analogue reception have to go to this amount of trouble in the hope that it might alleviate some or all of the problems.
At the end of the day (Part 2!) my cellphone, DECT cordless, DAB radio, NICAM stereo TV and all my digital satellite receivers are fine when buses go past and - apart from satellite - they don't require such extraordinary measures for that to be the case.
You can't compare your Freeview box with a Nicam stereo TV. Again, the Freeview box has much greater processing power and has to cope with something like 5 channels squashed into the space of one - video, audio and all the extra features - PLUS it has to winkle out a really weak digital signal from between your belting analogue signals. Little wonder that it's prone to occasional glitches from electrical interference if you use the wrong cable.
(Try using TV aerial cable for your Sky Digital dish and see if it works! Be sure to fit an unshielded wall socket, too.)
Did you know that ordinary aerial coax "shielding" is only 60 percent effective at best? Bearing in mind that analogue transmissions will be turned off in a few years, it makes sense in a new house to spend a few extra pennies on the proper cable, even if you don't plan to use it at present.
But to be fair neither are you. The key point about digital terrestrial TV is that it is meant to be an easy, plug and play proposition.
Anyone with a reasonably good analogue signal, recieving from a transmitter broadcasting a DTT signal should be able to plug-in a set-top box and watch digital TV.
The problem is that for many people it doesn't. Whilst I'm not doubting that using good quality cable, high gain antennas etc all significantly help to improve digital reception - many people are already using standard TV aerials with cheap cable which work perfectly well for analogue - and are utterly hopeless for digital reception.
Telling people that they must re-cable their entier house and spend a fortune on new TV aerials just so they can get UKBrightIdeas is not really the best way to drive take-up of a digital TV reception.
Sam, I understand the point you're making and you're right that it is kind of incredible what these boxes do considering what dedicated home computers did at the beginning of the nineties. But, at the end of the day, DTT has problems that other forms of digital transmission do not. Okay, I'm not that technical and don't know the details of what's behind those different technologies - all I know is that DAB's fine (despite it being an older and fairly similiar - to an extent - technology) as is DECT, cellphones, NICAM and DSAT. But of course it's chalk and cheese and I'm looking at it from a more consumer stance than a tech one.
Who told you that?
If you type your postcode into the Freeview availability web site I bet it tells you that you "may need to change your aerial". That's not "plug and play" (mind you, nor is Windoze or Mac for that matter!)
http://www.freeview.co.uk/canireceivefreeview/
Most people have put up with barely watchable analogue pictures for years. They've got a twenty-year-old "contract" aerial and cable which should have been replaced years ago but they haven't noticed the gradual picture degradation because with analogue it starts with just a faint "graininess". Unfortunately, with digital transmissions being some 27dB weaker to begin with, your "faint graininess" on analogue becomes total dropout with digital.
Bear in mind, too, that in some areas the digital muxes are at the top of the frequency band and the analogue are at the bottom. So the aerial that works perfectly well for "band A" is totally useless for "band C/D" and you have no option but to change it as it's the wrong aerial.
In this particular case, it's like expecting to get good analogue pictures from your FM radio aerial.
So you absolutely must not expect "plug and play". Some people will be lucky but many won't.
But I would've thought most people go in to the likes of Dixons, Currys and Comet to buy things like this after seeing adverts in the tabloids. Most people don't think about checking websites first, we're in the minority.
Most people I know have pretty good aerials that are good for the main four channels and often for the fifth. Plus the digital muxes are right between the analogue ones. Teletext and NICAM are usually fine on the main sets of these households. If these people have no hope of getting a steady "Freeview" picture downstairs they stand no chance on their other sets (I think I'm the only one that has any additional outlets, everyone else uses the wirey things that come with portables for their second, third, fourth and fifth sets).
Still cant get the box to stop freezing everytime somebodys bloody mobile goes off though... :rolleyes:
As for Greg Dykes statement
quote:
...you no longer get interference if a bus goes by or you open the fridge door
I think for most of the original ITV Digital subscribers this is true, those MUX's that went 16 QAM have definately imroved there is no doubt, however the MUX's that are not part of Freeview (2 & A) still suffer the same old problems.
Yes but the adverts and shops should be truthful. They can't just
suggest "plug and play" if it's not certain.
Extract from the Digital TV Group R Book 2 "Installing Digital Terrestrial Television – Domestic Systems":-
In some cases (e.g. Crystal Palace) all six multiplexes are close to
the analogue channels and so are within the group of channels covered
by existing receiving aerials. In others (e.g. Black Hill) some
multiplexes are close to the analogue channels whilst the remainder
are several channels removed, and may be received poorly on
existing aerials. Cases where all six multiplexes are far removed
from the analogue channels are rarer, but do exist (e.g. Waltham).
So it's not certain at all and, in these areas, it's pretty sure that it won't be "plug and play".
Sam
But we're living in the real world and that's never going to happen. DTT has long been seen as the easy route to digital TV - no fussing with having an "engineer" out to make holes in your walls and, in the case of CATV, your garden.
If you ask those that have got DTT or are interested in getting it they'll usually state this for being one of their main reasons for getting it. It's up there with the "over my dead body am I giving money to Murdoch", "I pay my TV Licence why should I pay more?" and "I can't have a dish - what will our neighbours think?"
Perhaps Freeview should make it more clear in their advertising that this is far from plug and play?
I don't think I ever said anything was certain. With regards to DTT reception, all bets are off!
The benefit of QAM-16 isn't that it completely removes the interference (it is still there) but that the amount of on-screen corruption is far less, resulting in more watchable pictures.
What probably masks this effect to a large degree is that when Freeview re-launched there was a "double-whammy" of not only a modulation change but a rise in transmitter ERP as a result of the 3dB power increases.
Even so, both the modulation change and power increases do not seem to have completely removed the problem of impulsive interference. Yes it's better than it was before, but Greg honey it really hasn't gone completely... as I can demonstrate when a crappy Routemaster bus drives past outside
Perhaps, similar to the 1950s when TV became popular and law was passed enforcing cars to be fitted with surpressors (which otherwise utterly ruined analogue VHF TV reception) the Government should pass another law so that cars, bikes and buses have to have low "impulsive interference" emissions as part of their MOT test