CP DSO The story so far!
 

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

CP DSO The story so far!
 

Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

--

CP DSO The story so far!
 

In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is this
real, or just some 'feature' of the analyser scan speed?
--
Ian

CP DSO The story so far!
 

Ian Jackson wrote:

In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is this
real, or just some 'feature' of the analyser scan speed?

I'm not LOS with CP. I've got Windsor Castle in the way. Could that be
the reason?

--

CP DSO The story so far!
 

In message , Ashley Booth
writes
Ian Jackson wrote:

In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is this
real, or just some 'feature' of the analyser scan speed?

I'm not LOS with CP. I've got Windsor Castle in the way. Could that be
the reason?

Indeed it could. It's probably because you've got a lot of 'close in'
(short delay) multipath/echoes/ghosts.

If the delay time is short enough, on an analogue TV picture, you might
not have noticed it as ghosting. On the spectrum analyser, all you might
see is the relative vision-sound RF levels are not quite 10dB*. However,
multipath usually immediately shows up as spectrum ripple on
'noise-type' signals, like QAMs.
*[It used to be 7dB, then 10dB when NIACM was added - or did they drop
it even further, to 13dB? Anyway, it's not relevant here.]
--
Ian

CP DSO The story so far!
 

Ian Jackson wrote:
In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is this
real, or just some 'feature' of the analyser scan speed?
Maybe the analyser isn't really designed for the purpose. Here's a
screenshot from a very old analyser, showing a nasty notch in the ch44
notch.
http://dl.dropbox.com/u/11023364/DSC00808a.jpg

Bill

CP DSO The story so far!
 

Ian Jackson wrote:

In message , Ashley Booth
writes
Ian Jackson wrote:

In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is
this real, or just some 'feature' of the analyser scan speed?

I'm not LOS with CP. I've got Windsor Castle in the way. Could that
be the reason?

Indeed it could. It's probably because you've got a lot of 'close in'
(short delay) multipath/echoes/ghosts.

If the delay time is short enough, on an analogue TV picture, you
might not have noticed it as ghosting. On the spectrum analyser, all
you might see is the relative vision-sound RF levels are not quite
10dB*. However, multipath usually immediately shows up as spectrum
ripple on 'noise-type' signals, like QAMs. *[It used to be 7dB, then
10dB when NIACM was added - or did they drop it even further, to
13dB? Anyway, it's not relevant here.]

Here's a shot of another analyser to show the ripple is real.
http://www.flickr.com/photos/snglinks/6905503798

When OnDigital first started the Muxes were such low power that I used
to lose signal for a few seconds every time a plane flew over. This was
quite often as I'm on the flight path to LHR.
I assume the reflection from the plane was adding then subtracting from
the direct signal as it flew over. LHR is on the same bearing as CP.

--

CP DSO The story so far!
 

Ashley Booth wrote:
Ian Jackson wrote:

In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/
"You must be signed in to see this content"
Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is this
real, or just some 'feature' of the analyser scan speed?

I'm not LOS with CP. I've got Windsor Castle in the way. Could that be
the reason?

The muxes ARE rather castellated.

Bill

CP DSO The story so far!
 

On Apr 6, 10:22*pm, "Ashley Booth" wrote:

Here's a shot of another analyser to show the ripple is real.http://www.flickr.com/photos/snglinks/6905503798


You must be signed in to see this content

Lars :)

CP DSO The story so far!
 

In message , Ashley Booth
writes
Ian Jackson wrote:

In message , Ashley Booth
writes
Ian Jackson wrote:

In message , Ashley Booth
writes
Andy Burns wrote:

Ashley Booth wrote:

http://www.flickr.com/photos/snglink...7629753754943/

"You must be signed in to see this content"

Try again. The first picture was marked 'restricted'
I've had to remove some text to get it removed :)

The QAM signals seem to have a hell of a ripple across them. Is
this real, or just some 'feature' of the analyser scan speed?

I'm not LOS with CP. I've got Windsor Castle in the way. Could that
be the reason?

Indeed it could. It's probably because you've got a lot of 'close in'
(short delay) multipath/echoes/ghosts.

If the delay time is short enough, on an analogue TV picture, you
might not have noticed it as ghosting. On the spectrum analyser, all
you might see is the relative vision-sound RF levels are not quite
10dB*. However, multipath usually immediately shows up as spectrum
ripple on 'noise-type' signals, like QAMs. *[It used to be 7dB, then
10dB when NIACM was added - or did they drop it even further, to
13dB? Anyway, it's not relevant here.]

Here's a shot of another analyser to show the ripple is real.
http://www.flickr.com/photos/snglinks/6905503798

When OnDigital first started the Muxes were such low power that I used
to lose signal for a few seconds every time a plane flew over. This was
quite often as I'm on the flight path to LHR.
I assume the reflection from the plane was adding then subtracting from
the direct signal as it flew over. LHR is on the same bearing as CP.


I remember that too, from Mendip.

It happened quite a lot, being on the flight path to South Cerney,
Fairford, Hullavington and Brize Norton. :¬(
--
Ian