So if it happens, change the cable. But freeview *can* work perfectly well without an enormous aerial array and CT100 all over the place. If you have a reasonable analogue picture, it will probably work fine.
They don't have too.
In article , tony sayer writes
I solder all my coax plugs/sockets, i.e. push the central core right through so that it pokes out the bit that plugs into the telly, video etc. In the loft I split the aerial down lead into two and use a bit of
15 mm copper pipe hammered oval as a shield. Works fine. A bit of aluminium corrosion between the junction of copper and coax plug is bad news for reception.
I wouldn't bet on it at those frequencies.
Believe whatever makes you happy. I can only give you the benefit of 16 years in the trade and thousands of digital installations carried out.
I believe what I see on my television screen and what a number of other people here have said. If you have good analogue Channel 5 reception then there's a very good chance that you will get digital FreeView with the same aerial installation. If not then an aerial upgrade is probably all that's necessary (assuming you haven't got a super-duper aerial already). Only if you're trying to squeeze the last few extra dB of signal out of the system is it worth upgrading the aerial cables and so on.
stuart noble mine to just suck it and see. Try the new aerial, then the new cable, then
I think that's the best approach, why spend time/money unnecessarily.
With digital, you will not see the problem until the signal drops below threshold, when there will be total picture loss after breakup. Consequently, you can only tell how reliable or not the installation is by taking measurements with the proper equipment.
It may be the case in some areas, but it depends on where the channel allocations are in the band. In the case of a group A analogue transmitter and group C/D digital, your theory is obviously incorrect.
You see, you have a little knowledge, but not enough to understand it fully. I could spend hours boring you with the science, but I don't really think you would listen then.
It has less to do with cable loss than screening pulse interference although cable tilt will tend to be worse on non spec cable. You will also find that the gorillas who install cheap cable in new builds often bend it too sharply or kink it. That gives rise to "suck out" in parts of the spectrum and can affect "flatness" of the multiplex(es) affected.
Not necessarily so that. You can have good analogue reception if say your local TX is in A group 21-34 but a digital MUX planted up near the top end of the band say channel 67 like hereabouts off sandy heath then this is stretching things a tad too much!.
An A group aerial is way, way, down on level at that separation and co- ax cables fall in efficiency as the frequency increases, and if they are of the very open loose weave braided types.
Anyway, why is it that people can spend a small fortune on TV's DVD players Home cinema and the like and yet be so penny pinching when it comes to a few tens of pounds for an aerial that will give an adequate signal that will cope with fades and give excellent service over many years, and thousands of hours of good quality service?.
Having worked in the TV industry at both ends for some years it still amazes me as to what crappy and poor reception people will put up with all for the want of a few quid's worth of metal!....
I'm in a strong signal area - close to Crystal Palace in SW London where there is probably more RF radiated than anywhere else in the country, and what you've also got to consider is spurious pickup of unwanted signals via the co-ax - normal UHF stuff is poorly screened.
Also, co-ax can deteriorate with age - I've seen it full of water. ;-)
I use radio mics a lot in my job, and the UHF versions of these are extremely sensitive to the type of cable used as they work at tiny powers. And the cable we use for more than very short runs is a great deal larger and more expensive than anything used domestically.
All too true. Several years ago (wisely?) put up a good aerial thinking it would be an idea to have one in the correct band A, rather than a generic wideband one. Perfect C5, rubbish at Freeview as it's on a different aerial group. Should have got a semi-wideband K? instead. Mind you, what do people watch on Freeview? Listening to 5live seems about the only thing worth having.
ITV2 has some good repeats - the original Morse series was on recently. BBC4 has some decent enough stuff too. Of course it depends on your tastes.
It's also probably the best source of radio, audio quality wise, since DAB rates have been set so low on many stations.
And assuming the programme source is up to it, the picture quality *is* better in many ways than the very best analogue - provided you feed the set with RGB. It has a wider luminance bandwidth, so can provide sharper pictures, and more noise free deep colours. It's not universally better, though, as some artifacts can be seen on some movement at certain times.
I don't agree. We live within 3 miles of Sandy Heath, which makes it easy to get an excellent signal, and of course it's easy to mess it up if you want to experiment...
I've found it's easy to have terrible analogue with near-perfect digital, excellent analogue with limited digital, and any combination in between. What's more, it's very easy to get stop-start digital, mostly glitchy digital, mostly OK digital, or digital which works most of the time but has a very slight freeze/jump once or twice an hour.
For now, we have a home made experimental log periodic aerial I made from plastic sheeting and aluminium foil, suspended from two nails in the loft. It cracked the analogue channel five problem (except in the middle of summer), but we get occasional jumps on digital BBC1 (not BBC4 though - strange, given the frequencies at Sandy Heath).
It's a pity this "free" aerial got so close, because it's now hard to justify the expense of sending a professional up on the roof.
Cheers, David.
P.S. This question would be more at home in uk.tech.digital-tv where you will already find many answers!
If the picture never breaks up or disappears then the signal is good enough. It doesn't take measuring equipment to show that.
If you are a business installing an aerial then it's a whole different ball game as you can't afford to prove the installation is good enough by watching it for a week in varying weather conditions. So measuring equipment is then useful, however not nearly so useful/necessary for a DIYer.
OK, but there are not so many areas where the digital MUXs are transmitted on frequencies a long way away from the analogue ones, the frequency planning has tried to minimise that. What I was really trying to say though was that if you can get a good channel 5 signal then you probably can get good digital reception with a similar type of aerial, quite likely in most areas the same aerial.
I have a degree in Electrical Engineering, worked at Marconi Instruments (who make signal generators) for many years, was a SWL for many years, etc., etc. I doubt if anyone "understand[s] it fully", one of the things one learns is that knowing more tends to open your eyes to how much you don't know.
It's mostly engineering not science in my opinion.
Is interference a serious problem with digital? Not only that but does cheap cable *really* let in more noise than expensive cable? Even at the frequencies involved the mesh of 'cheap' cable must be pretty well impervious to signal getting onto the downlead, does the extra aluminium foil of more expensive cable really help in reducing interference pick up or is it much more to do with reducing attenuation (or is it even more to do with selling soemthing expensive unnecessarily)?
Nice to hear the tech-nick-ally noll-ijjable confirm what my own unsystematic A-B comparison suggested. Our TV does take an RGB feed from the Freeview decoder (passing it hopefully unmangled through the video recorder's pair-o-scarts: only 2 scarts on the TV with one dedicated to DVD). What with the better picture, and the more useful Guide for a greater-depth "now-and-next" listing, we've taken since having the Freeview box in at the start of the year to watching even the mainstream channels through the FV box.
Stefek
I'd be most surprised if the VCR looped through RGB. And has your set two RGB SCARTS?
In article , Dave Plowman writes
Do call in if you're up this way (Cambridge) Dave anytime to do an A/B twixt analogue and digital. But then again is the feed to Crystal Place all that good these days?....
Well, at one time it was the source of emergency analogue RBR so I assume they keep it up to scratch...
Had a distorting limiter some years ago on BBC 1 and nobody at the BBC would believe me - I can get Hannigton here to and could switch between them.
FSVO "never" (such as "never, ever, ever") perhaps.
A couple of points here: firstly, many contributors to this thread have said that they can get DTT reception, despite the postcode database (which does err slightly on the cautious side) predicting otherwise. Be aware that signal strength alone is not the only issue. Every UHF channel is re-used hundreds of times over and coverage is mostly limited by co-channel and adjacent channel interference from other TV transmitters, rather than by thermal noise. Now, as many will be aware, UHF propagation is seriously affected by certain weather conditions which give rise to 'tropospheric ducting', increasing the signal levels from remote transmitters by large amounts and causing severe interference[1]. The statistics of this effect are well-studied and DTT coverage is planned to work for 99% of the time (c.f. 95% of time for analogue TV). Some of those receiving in areas which are not officially classed as 'covered' can expect to experience tropospheric interference for more than 1% of the time.
Secondly, in the absence of any test equipment, a simple test of signal margin is to insert a 3 dB attenuator pad at the receiver input. If this leads to reception failure then your signal is somewhat marginal.
Oh yes there are: look at Belmont, Sandy Heath, Wenvoe and Waltham, to pick four examples of main transmitters which have some of the mux's well outside the original analogue group.
And has concentrated on population served: thus Crystal Palace, Sutton Coldfield and Winter Hill get more-or-less in-group DTT channel allocations, but for the rest of the country it's much more patchy.
I think you're just introducing a red herring in suggsting that DTT reception will be correlated with analogue C5 (which is not even radiated from many TX sites). In any case very few people upgraded their aerials for C5, so the existing one will most likely match the original 4-channel plan group.
No, it's not a con. What Andy L was talking about there is 'impulsive interference' - interference from sparking contacts - to which DTT is quite sensitive. Impulses propagate on, and are radiated from, mains wiring, and thus are much stronger in the house and loft than above the roof (which provides some screening). A well-screened coax downlead from antenna to receiver will largely prevent impulses entering the signal path. With poor screening, a coupling mechanism exits to allow impulse energy into the receiver, resulting in the familiar momentary 'freezes' and clicks.
Using well screened coax is necessary, but not sufficient. Any gaps in the screening will allow the interference to get in, and poorly screened outlet plates and flyleads are the other betes noir. At the other end of the coax, the lack of a balun on the aerial will also provide a coupling mechnanism. This is all sound theory, and has been verified experimentally in tests done under controlled conditions. Oh, and an aerial in the loft is likely to be close to mains wiring, so is asking for trouble.
With a really well-screened system and a decent receiver you can get solid reception with signal levels down to 35 dBuV, even on the 64-QAM muxes (ITV/C4 and SDN). With grotty brown open-weave coax and a typical outlet and flylead, you may need 45 or even 50 dBuV before the signal is strong enough to swamp the impulse interference.
[1]
Not sure about the first, as the VCR (very recently bought Panasonic) has naff-all documentation. It's vaguely plausible that it does, as I've told the Freeview box to push out RGB rather than composite video, and there's a signal visible on the TV; however it's also possible that the menu lies and the RGB is an "also" rather than an "either".
As for the second (pops downstairs to retrieve the TV's Book Of Words...) well, it seems that the set (also a Panasonic) does not have two RGB Scarts. The first one, to which the VCR and transitively the Freeview box connect, is RGB-capable. The second is not RGB-capable, but is S-Video capable, so I *think* the DVD player is sending a plausibly-decent signal to the TV through that route. It's possible there could be some marginal benefit from swapping these two inputs round, with the DVD player going to the RGB-capable one and the VCR to the other one; but then I might get a less good signal from the Freeview box, which has to feed into the VCR for recordability. Ah, choices, choices... and it'll get more funky still if I do revive the satellite receiver!
One can't help concluding there's a tension between providing minimal-cost caters-for-most-cases-adequately connectivity which doesn't confuse the consumer population at large, and providing flexibility and a high-quality signal path for a variety of devices (well duh!). SCART connections seem to have acquired quite a few bits of added-on Flexibility, stretching the pin assignments beyond the initial design with its simplistic "look at me! I've asserted +5V on the look-at-me line, so look at me!" idea... but I don't see anything else (Firewire/mLAN?) becoming a universal, self-configuring, self-describing, digital, easy-to-interconnect consumer AV interconnect standard just yet. Unless (shudders at memory of amusingly-shaped vegetable and over-prominent teeth) You Know Better?
Stefek
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