Poor reception of ITV channels on Freeview

A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC channels
are OK). The antenna setup hasn't changed. Any ideas? My antenna is pointed
at the Crystal Palace transmitter.

Peter

"Peter Barns" wrote in message
...

A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC
channels
are OK). The antenna setup hasn't changed. Any ideas? My antenna is
pointed
at the Crystal Palace transmitter.

It is my experience that Multiplex 2 (which carries the ITV channels) on
Crystal Palace always has a much lower signal strength than the others. I
don't know whether this is a general experience; all the multiplexes are
supposed to be 20 kW.

--
Max Demian

Peter Barns wrote:
A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC
channels are OK). The antenna setup hasn't changed. Any ideas? My
antenna is pointed at the Crystal Palace transmitter.

The antenna setup may not have changed , but it could have been blown about
in the recent crap weather just enough to move it slightly offline and
affect that particular multiplex

--
Alex

"I laugh in the face of danger. Then I hide until it goes away"

www.drzoidberg.co.uk www.ebayfaq.co.uk

In article , Max Demian
wrote:
"Peter Barns" wrote in message
...

A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC
channels are OK). The antenna setup hasn't changed. Any ideas? My
antenna is pointed at the Crystal Palace transmitter.

It is my experience that Multiplex 2 (which carries the ITV channels) on
Crystal Palace always has a much lower signal strength than the others.
I don't know whether this is a general experience; all the multiplexes
are supposed to be 20 kW.

IIRC The mux for ITV1 uses 64QAM, whereas most use 16QAM. This means
that more power may be needed to get a satisfactory result.

Slainte,

Jim

--
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Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Peter Barns" wrote in message
...

A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC
channels
are OK). The antenna setup hasn't changed. Any ideas? My antenna is
pointed
at the Crystal Palace transmitter.

Peter

There is a difference in the data modulation technique used between the BBC
and commercial TV stations which means even at the same signal levels the
BBC channels will be more robust.

BBC channels use a system of 16 QAM (encodes 4 bits or 16 states per symbol
period) whereas the commercial stations (ITV etc) use 64 QAM (encodes 6 bits
or 64 states per symbol period).

The reasoning being that for a given bit rate you will use less bandwidth
for a 64 QAM system, allowing you to transmit more channels within a given
multiplex.

The cost, of course is poorer signal/noise ratio and increased frequency of
dropouts.

HTH

Anna

"Dr Zoidberg" wrote in message
...
Peter Barns wrote:
A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC
channels are OK). The antenna setup hasn't changed. Any ideas? My
antenna is pointed at the Crystal Palace transmitter.

The antenna setup may not have changed , but it could have been blown
about in the recent crap weather just enough to move it slightly offline
and
affect that particular multiplex

Yes, that does seem likely

Peter

Peter Barns wrote:
A few days ago the reception of ITV channels on my Freeview box
deteriorated. It seems to affect some channels but not others (BBC channels
are OK). The antenna setup hasn't changed. Any ideas? My antenna is pointed
at the Crystal Palace transmitter.

About the same time (I noticed it on the ninth, when the OH had to watch
x-factor through analogue!), my itv went dodgy.. that's on pontop pike.

Could be the weather? Things seem ok now.