Digital set-top boxes (slightly O/T) - weak signal area.

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It's not that long ago that post production - editing and dubbing - caused pretty severe degradation of the studio stuff - even before the average domestic telly got to work. But since DigiBeta arrived, and the better digital dubbing systems, if things are well done the difference is near undetectable. And there are some very good TV sets around these days too, as well as plenty of dross.
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*Half the people in the world are below average.

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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On Tue, 6 Jan 2004 08:37:34 -0000, "stuart noble"

Yes. I use a loft aerial and amp setup to feed 3 TVs and a freeview box.
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Niall

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Niall wrote in message ...

little
That's encouraging. I wonder if the "51 element" aerial Chris refers to could be connected to the original cable, or would it need new cable?
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It is a very good idea to replace the nasty old cheap brown co-ax with decent low loss cable.
Christian.
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On Wed, 7 Jan 2004 11:41:12 -0000, "Christian McArdle"

If you need to. If you get 100% signal on all muxes, why bother. I did replace one length as a precaution, as it wasn't even UHF coax and had a couple of taped splices in, but only with ordinary TV coax from B&Q. There was also a dodgy connector which needed replacing.
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Niall

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Because the HF loss is greater than decent cable, but mostly because the screening of ordinary cable is inadequate to keep pulse interference out, which can lead to breakup.
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AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk
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On Wed, 7 Jan 2004 18:40:11 +0000, "Andy Luckman (AJL Electronics)"

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.
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Niall

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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.
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AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk
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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.
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Chris Green ( snipped-for-privacy@x-1.net)

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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.
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AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk
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Andy Luckman (AJL Electronics) wrote:

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.
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Toby.

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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.
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*According to my calculations, the problem doesn't exist.

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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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
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I'd be most surprised if the VCR looped through RGB. And has your set two RGB SCARTS?
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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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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The easy way to check is by slowly removing/connecting one of the SCART cables at an angle - you can usually make one of the RGB feeds break up first.
It's often difficult to tell - there isn't always a vast difference depending on programme material.
But if the VCR is looping through RGB, I'd expect it to also have to convert RGB internally as well for recording purposes. Now some Philips ones do or did, but it's not common.
An RGB SCART also carries composite in and out. It's a devilish system to get your head round at times.
I built an RGB DA to feed the ONDodgy box to the set in the kitchen as well as the main set. The STB obviously is powered all the time, but the DA is powered off my Audio/TV supply that all switches from the AV amp on/off. If I power down the DA, and leave everything else on, the kitchen set reverts to composite off the SCART cable since this is looped straight through - it's only supplying the syncs so I didn't bother with 'DAing' it. And often you can't tell the difference. Seemed like a good idea at the time...
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*Windows will never cease *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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"Dave Plowman" wrote in message
[Detecting whether the TV is using an RGB feed]

There's an easier way than that: if the TV is using RGB then its colour (saturation) control will have no effect. If the picture goes to black and white when you turn the colour right down, the interface must be either composite or Y/C, not RGB.
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Andy



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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?....
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Tony Sayer


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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.
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*The statement below is true.

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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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)?
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Chris Green

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