[linux-dvb] Re: Signal Strength (was: private channels on Telekom cable)

[Mathias Born <mborn@faphida.in-berlin.de>]

Thursday, September 20, 2001, 8:33:48 AM, Markus Erhardt wrote:

>> Don't underestimate this digital technology. DVB-s can be received
>> 100% error free even if the signal power is so small that no analog
>> reception would be possible.

ME> is this true? I've got a WinTV Nova and used the Windows-Software to test
ME> the Signal Strength. It was 53% with my old 60cm dish, with the new 85cm
ME> dish it is 64%. There is a big tree in front of the dish, so the signal

Ok, this statement was a bit too general. What I wanted to say was
that transmitting digital signals normally doesn't need such a high
signal to noise ratio as the old analog system needs.
(But this depends on the design of the whole system.)
You can see this for example when comparing normal FM radio with DAB
radio. The quality of DAB remains constant independent of your
distance to the sender (due to error correction of the channel coder).
The reception becomes inpossible only when you pass a threshold
distance.
Using an analog FM radio the noise you hear gets louder the
larger the distance between you and the sender is.

Concerning your satellite dish: of course, the signal that approaches
your location (behind the tree) is as weak as it is. But using a
larger dish you can "collect" more of it, thus raising the signal
power your receiver gets.

ME> strength can't get better. Last winter I had around 60% with the old dish.
ME> The analog signal is quite good. Should the digital signal be also good?

Yes it should!
What do you mean with "quite good"?

I suppose the signal strength is derived from the bit error rate by
the software. Then it is reliable in a sense that you need nearly
100% :-(

-- 
Tbs,
 Mathias Born



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