ddrichardson at btinternet.com
Sat Nov 3 21:12:44 GMT 2007
On Sat, 2007-11-03 at 20:49 +0000, norman wrote:
> Perhaps the terms I used are not technically correct. My experience is
> as follows:- I bought a length of 10 metres of what I call ordinary TV
> cable, from my local hardware shop and used it run an extension to my
> computer so as to run Mythtv on digital channels. When I came to scan
> for channels there was insufficient signal strength to get a lock. So,
> with digital TV in mind, I replaced the cable with a length of so called
> sky cable and the signal strength was much better and Mythtv worked.
> The cross section of the two cables is quite different and I suspect
> there is a difference in impedance and is really nothing to do with the
> difference between digital and analogue signals signals, or is it?
Ah I see, I hadn't considered the routing of cables indoors. The chances
are the difference in cross section are less in impedance but more
related to the shielding afforded the cable. Coaxial cable can be a real
pain - especially in systems where voltage standing wave ratio is an
issue. Because you are not transmitting but only receiving though this
is not a problem with TV reception, its interference that causes the
Digital transmission is essentially the same as analogue, from the point
of view of how the signal is physically transported. The problem is that
a digital signal once decoded tends to lose resolution (I mean
resolution in the transmission sense not the display sense) when there
are signal problems - you either get a signal that works or not.
Analogue often gives a poor but usable picture.
More information about the ubuntu-uk