Why is Digital TV more affected by weather?

[Bear]

You would think it would be the other way around....
Pops crackles, frame dropouts etc seem to be the norm in a storm

[Nicholas Buenk]

A storm produces a lot of interference you know...
"Bear" <who@where.com> wrote in message
news:41216706$0$16347$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
> You would think it would be the other way around....
> Pops crackles, frame dropouts etc seem to be the norm in a storm
>
>

[mddawson]

A storm produces a lot of interference you know...
"Bear" <who@where.com> wrote in message
news:41216706$0$16347$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
> You would think it would be the other way around....
> Pops crackles, frame dropouts etc seem to be the norm in a storm
>
>

How was/is your analog reception. If it wasn't that good and you are using the same antenna for your digital setup, this could be the problem.

With analog as signal strength decreases, you will get a gradual reduction in picture quality (ghosting, grainy picture, etc.)

With digital you have the cliff effect, that is a perfect picture as signal strength reduces until a point (say 50-60% strength) when you will get nothing.

If your antenna and cabling isn't up to scratch, you may be running at 70% strength on a fine sunny day - along comes a storm and you loose a little signal strength through interference that may be enough to loose you picture.

[Nicholas Buenk]

"mddawson" <mddawson.1b4arm@no-mx.forums.eyo.com.au> wrote in message
news:mddawson.1b4arm@no-mx.forums.eyo.com.au...
>
> Nicholas Buenk Wrote:
>> A storm produces a lot of interference you know...
>> "Bear" <who@where.com> wrote in message
>> news:41216706$0$16347$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
>> > You would think it would be the other way around....
>> > Pops crackles, frame dropouts etc seem to be the norm in a storm
>> >
>> >
>
> How was/is your analog reception. If it wasn't that good and you are
> using the same antenna for your digital setup, this could be the
> problem.
>
> With analog as signal strength decreases, you will get a gradual
> reduction in picture quality (ghosting, grainy picture, etc.)
>
> With digital you have the cliff effect, that is a perfect picture as
> signal strength reduces until a point (say 50-60% strength) when you
> will get nothing.
>
> If your antenna and cabling isn't up to scratch, you may be running at
> 70% strength on a fine sunny day - along comes a storm and you loose a
> little signal strength through interference that may be enough to loose
> you picture.

Yes, however a storm produces so much interference that it's possible than
even with as 90% signal strenth you might get some data corruption. And data
corruption looks worse on digital than analogue.

[mddawson]

"mddawson" <mddawson.1b4arm@no-mx.forums.eyo.com.au> wrote in message
news:mddawson.1b4arm@no-mx.forums.eyo.com.au...
>
> Nicholas Buenk Wrote:
>> A storm produces a lot of interference you know...
>> "Bear" <who@where.com> wrote in message
>> news:41216706$0$16347$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
>> > You would think it would be the other way around....
>> > Pops crackles, frame dropouts etc seem to be the norm in a storm
>> >
>> >
>
> How was/is your analog reception. If it wasn't that good and you are
> using the same antenna for your digital setup, this could be the
> problem.
>
> With analog as signal strength decreases, you will get a gradual
> reduction in picture quality (ghosting, grainy picture, etc.)
>
> With digital you have the cliff effect, that is a perfect picture as
> signal strength reduces until a point (say 50-60% strength) when you
> will get nothing.
>
> If your antenna and cabling isn't up to scratch, you may be running at
> 70% strength on a fine sunny day - along comes a storm and you loose a
> little signal strength through interference that may be enough to loose
> you picture.

Yes, however a storm produces so much interference that it's possible than
even with as 90% signal strenth you might get some data corruption. And data
corruption looks worse on digital than analogue.

I should have also mentioned that digital TV is still in its infancy and that perhaps the current crop of STBs are not as immuned to interference and the like that later generation STBs probably will be.

[NFP]

Bear wrote:

> You would think it would be the other way around....
> Pops crackles, frame dropouts etc seem to be the norm in a storm

AFAIK, digital TV in Australia is based on a transmission method that is
relatively immune to multipath reflection (the kind that gives ghosting
in analogue) but susceptible to impulse noise (eg arcs and sparks from
switches, atmospheric discharges, etc).

Interestingly I believe the digital TV system the USA uses has the
reverse problem: more immune to impulse noise but susceptible to
multipath reflection problems.

[Daniel Franklin]

NFP wrote:

> Interestingly I believe the digital TV system the USA uses has the
> reverse problem: more immune to impulse noise but susceptible to
> multipath reflection problems.

It is probably fair to say that the modulation scheme used in the US is
inferior in every respect, including being more complex to implement :-)

Theoretically, COFDM should actually be pretty resilient to impulse noise
(due to the comparitively long symbol period). In practice it is less so,
however there is a lot of research going on at the moment into ways to make
it more robust...

- Daniel
--
************************************************** ***********************
* Daniel Franklin - Lecturer in Computer Engineering
* University of Wollongong, NSW, Australia * d.franklin at ieee.org
************************************************** ***********************

[OzDuDe]

Daniel Franklin wrote:

> It is probably fair to say that the modulation scheme used in the US is
> inferior in every respect, including being more complex to implement :-)

I thought that 8-VSB was not unlike the analogue system used to transmit
PAL and NTSC analogue? The difference essentially being that it's
carrying digital, rather than modulation data?

If that is the case, then I can't see how the 8-VSB
transport/transmission could be more immune to impulse noise than COFDM,
by it basic theoretical nature.

Impulse Noise is after all, a micro-cessation of the original signal.
>
> Theoretically, COFDM should actually be pretty resilient to impulse noise
> (due to the comparitively long symbol period). In practice it is less so,
> however there is a lot of research going on at the moment into ways to make
> it more robust...

I've just recently been reading about this myself and it's fascinating
what is being researched. I think we are lucky actually that we have
COFDM over OFDM (UK I believe) and 8 VSB ;)

Oz

[bassett]

The American system of digital transmission uses Circular Polarisation, we
use Linier.
As for picture breakdown This is why digital has something called "Forward
Error Correction" This looks at the signal , any variations in signal
strength and it simply shuts down, resulting in a black screen

<OzDuDe> wrote in message
news:412525ef$0$27732$afc38c87@news.optusnet.com.a u...
> Daniel Franklin wrote:
>
> > It is probably fair to say that the modulation scheme used in the US is
> > inferior in every respect, including being more complex to implement :-)
>
> I thought that 8-VSB was not unlike the analogue system used to transmit
> PAL and NTSC analogue? The difference essentially being that it's
> carrying digital, rather than modulation data?
>
> If that is the case, then I can't see how the 8-VSB
> transport/transmission could be more immune to impulse noise than COFDM,
> by it basic theoretical nature.
>
> Impulse Noise is after all, a micro-cessation of the original signal.
> >
> > Theoretically, COFDM should actually be pretty resilient to impulse
noise
> > (due to the comparitively long symbol period). In practice it is less
so,
> > however there is a lot of research going on at the moment into ways to
make
> > it more robust...
>
> I've just recently been reading about this myself and it's fascinating
> what is being researched. I think we are lucky actually that we have
> COFDM over OFDM (UK I believe) and 8 VSB ;)
>
> Oz

[Bruce Graham]

I was watching my Teac DVb420 last night thru its first thunderstorm - to
my surprise there were zero glitches and I'm in a poor signal area.

[Louis Solomon [SteelBytes]]

I find thunderstorms don't usually upset my recption, but my neighbour's
vespa piaggio scooter does screw up my ch10 (using a 'dodgytec' 2000 hd stb)

--
Louis Solomon
www.steelbytes.com


"Bruce Graham" <jbgraham@nowhere.com.au> wrote in message
news:MPG.1b92bd7552914584989760@news.optusnet.com. au...
>I was watching my Teac DVb420 last night thru its first thunderstorm - to
> my surprise there were zero glitches and I'm in a poor signal area.

[Richard Johanson]

Check rain doesn't get into the junction box where the cables go into your
house. Apparently these boxes aren't waterproof. say this as ours never
worked properly until the tech discovered the splitter was full of water.
"Louis Solomon [SteelBytes]" <louis@steelbytes.spam-is-bad.com> wrote in
message news:4128b04a$0$27216$61ce578d@news.syd.swiftdsl.c om.au...
> I find thunderstorms don't usually upset my recption, but my neighbour's
> vespa piaggio scooter does screw up my ch10 (using a 'dodgytec' 2000 hd
stb)
>
> --
> Louis Solomon
> www.steelbytes.com
>
>
> "Bruce Graham" <jbgraham@nowhere.com.au> wrote in message
> news:MPG.1b92bd7552914584989760@news.optusnet.com. au...
> >I was watching my Teac DVb420 last night thru its first thunderstorm - to
> > my surprise there were zero glitches and I'm in a poor signal area.
>
>