Mains interference: Digital TV problems

(snip)


I wouldn't bank on it - the whole thing seems to have been done on the cheap with no real thought for the viewers - logos on-screen which risk burning-in on your TV screen, a useless program guide, and equally useless Teletext.
Thank god for DVDs!
--
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Dave
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John wrote:

CAI membership doesn't count for much. Their members give *very* variable service. Some of the best aerial installation companies out there are not members so go by recommendation and read up on the subject. If it costs more than 100 just to get a decent aerial signal you may as well go FreeSat.
See uk.tech.digital-tv where this would be more on-topic.
-- Adrian C
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I always considered CAI installers as being in the upper part of the quality range - perhaps mistakenly.
For a marginal area Freesat is probably the way to go. I've also heard some horror stories about Sky's installers but that's for another thread.
Good Luck
John
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On Sun, 11 Jun 2006 13:07:28 GMT, Dave Ryman

Not really. A digital signal is easier to retain all of the signal due to the fact that a lot of FEC gets sent with the signal.

I use a regular antenna. I only miss on one local station. I actually used to get it from 20 miles farther away... over hills.
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On Sun, 11 Jun 2006 00:52:11 GMT, Dave Ryman

Standard F are fine done properly, and you will end up with more breaks in the line with BNC as you'll have to convert back and forth to hook up to all standard gear.
Yes, you must cut (prepare) all of your fittings carefully as well.
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By F-connector, I assume you mean the metal connectors that screw onto the shielding and outer insulation of the coax, and have the wire sliding into a centre pin. I have actually found one of these now that has a grub screw to make contact with the main centre wire: The standard ones here in the UK usually just depend on the wire making contact by sliding into centre pin - very hit and miss. I trust the average water pipe connector more - and that's saying something!
Thanks for that.
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Dave
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Dave
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One other item - each splitter degrades the signal by 3 db minimum (cuts it in half) just to split - so you get one-fourth of the input out of each leg of a two-way splitter - so minimize the splitters
(and to minimize noise - if you connect to two input devices with input coax -dvd, vcr, cable box, etc, - you need to break the metal shield on the coax at the input to one of the devices or the resultant loop of coax shield-chassis-coax shield/ chassis-coax shield will act like a loop antenna for nearby interference)

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That is correct. You should have stopped there!

If it were 1/4 to each leg, that would be a 6 dB drop, but it is 3 dB as you stated originally. That is half the power to each leg. (In fact it is probably more like 3.5 dB, as there is approximately 0.5 dB loss in the hybrid itself.)

That is not true. Do *not* break the outer shield on a coax cable. If you do, then you *will* get an antenna instead of a transmission line.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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On Sun, 11 Jun 2006 13:22:48 -0800, snipped-for-privacy@apaflo.com (Floyd L. Davidson) Gave us:

I think that he was thinking of an audio patch cord there.
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us:
snippitude

So now you are saying that he needs a new/better tuner?
Bit-error-rate... that is the term you are looking for.
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Gave

he
Not in the computer sense per se, but perhaps in the digital signal to ratio sense -
What I am saying is that since digital "amplifiers" do not amplify a signal as in an analog fashion, passing all the signal, rather they recreate the signal at a higher level, isolating at each stage, they are susceptible to creating extra bad bits in noisy signals. That is, while an analog amp will give you most of what comes in, a digital output is only reproduced timewise from what comes in. ( Removes the need for good filters and such.)
A digital amplifier's weakness, however, is that it is looking for a bit to reproduce - and it only "recognizes" signals having a certain risetime -it discriminates against signals rising too fast for the amp ( it can't "trigger") and it discriminates against signals that rise too slowly (the "gate" set by the clock closes before the voltage level rises enough to trigger an output).
If you look at a real digital signal, you will see a series of pulses and noise (non-signal) - if the noise is well below the level of the pulses, the pulses drive the amplifier and low noise has little effect - the bits are pretty much repeated and thus cleanly reproduced at a higher level. If the level of the pulses are weak and thus are in the noise, then there are too many false output bits created for a coherent signal. It does not discriminate properly between noise and signal.
( A "better" tuner would fix the problem only because the word better implies one that does not have the problem -) a "better at handling low signal to noise ratio" tuner might fix the problem, but normally you get what they give you and expect you to get the signal up to a certain strength and above a certain signal to noise ratio
(if that ability to discriminate in high noise is what is called bit-error-rate in digital signals, then that is the term.)
fwiw
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us:

Wrong. It is not a term that has ANYTHING to do with computers.
It is a COMMON term used in MPEG2/digital audio video transmission jargon.
ANY compressed, digital, A/V signal that uses FEC for correction of bad data uses THIS TERM to refer to signal quality.

You keep forgetting about the FEC. There is enough of it such that even missing segments of the signal can be replaced. Up to generally about ten percent.
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us:

Tell us... oh DIPSHITTO...
What is QAM 256?
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Gave

A way to cram more shit into the pipe.
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us:

Damn! You got one right!
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