Re: Strength or no errors?
- From: Jim Lesurf <jcgl@xxxxxxxxxxxxxxxxxx>
- Date: Tue, 04 Oct 2005 16:53:37 +0100
In article <1128427103.491831.141390@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
spiney
<sparkistuf@xxxxxxxxxxxxx> wrote:
> Reply to Bob, Jim, others, etc ......
> Clearly, Jim Lesurf doesn't understand digital tv too well.
Given your own level of "understanding" I think I would have been more
worried if you thought I *did* understand it... ;->
[snip]
> To demonstrate the knee, feed your aerial through a UHF variable
> attenuator (about £10), then split 2 ways, one way to analogue tv set,
> the other way to a Freeview receiver (and tv). Have 1 analogue and 1
> digital channel showing. Slowly attenuate signal. The analogue channel
> gets increasingly noisy, the digital one shows no difference until a
> certain point, then suddenly stops. Continue increasing attenuation, but
> the analogue channel is still there. That's the digital knee!
I'd interested to know how you do that whilst ensuring the attenuator does
not affect the levels of II (and other environmental noise as distinct from
RX noise) getting from the antenna to the RX. :-)
I am impressed, in a way, though, by your determination to keep ignoring
the real-world effects of II, fading, etc, etc.
[snip]
> As for the article Jim mentioned, I just can't see the point.
<ahem> :-)
> Yes, another test, but so what? No DTT-T receiver can cope with burst
> errors, there's just no way to do it! Even re-designing cofdm would give
> no better performance (that's why I found the article's remarks
> pointless, or perhaps deliberately sarcastic?!).
Perhaps you have not yet realised that II events at the RX will appear with
a variety of power levels and durations.... If you realise this, perhaps
you can then see why their levels compared with the carrier will affect the
situation from one event to another. Then realise why your "no DTT-T
receiver can cope with burst errors" neatly misses the point (again). ;-)
However that might then lead you to understanding the purpose of the paper
you referenced and then described as "useless"...
[snip]
> (for comparison with cofdm, when did you last get impulsive interference
> on Sky satellite?).
Afraid I don't have a satellite TV system, so can't comment on that.
However if you want to shift up to above 30GHz then I may be able to help
more with such questions... :-)
> COFDM is one in a long line of broadcasting formats, developed for
> political rather than technical reasons, where the originators got it
> significantly wrong, but still can't stop patting themselves on their
> collective backs.
Have you told them? :-)
Slainte,
Jim
--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html
.
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