Simple systems with a HDD
 

On Wed, 25 Apr 2007 13:36:29 +0100, tony sayer
wrote:

In article , Don Pearce
writes
On Wed, 25 Apr 2007 11:54:26 +0100, tony sayer
wrote:

In article , Don Pearce
writes
On Wed, 25 Apr 2007 10:21:49 +0100, tony sayer
wrote:

In article , Dave Plowman (News)
writes
In article ,
tony sayer wrote:
Just local roads round Balham and area. One place I go for a coffee has
I'd say pretty high RF levels and that's a good test for the receiver
distortion. It's fairly close to CP - but tuning into Wrotham doesn't
cure the distortion. All using R4. Distortion on speech is easier to
assess than on most music.


I've got to go and collect a transmitter from Croydon before long I'll
have a wander round that area..

Right. Stop for a coffee at the cafe at the top of Streatham common - easy
parking there. See what R4 FM sounds like. I must say I've not tried the
new radio there yet, but all the others sound pretty horrid.


Noted....


Don't you use the CP relay the one offset from Wrotham?..

What are the frequencies of the various relays around here (London).
In theory for Radio 4, my best signal should be 93.5 but most of the
time I seem to be getting a much more solid signal below that - can't
remember what, but maybe 93.0.


There is a system where crystal place relays Wrotham with something like
a 384 odd kHz offset there is a BBC engineering paper on it somewhere!..

Really? I guess that just manifests itself as a frequency error in my
car radio then, it only manages 50kHz steps.

Apparently thats not supposed to happen. I'll see if I can remember
where it is, its on line somewhere!...


I'll be interested...


I have to agree with Dave, though that driving around London FM is in
a constant state of swooshing, with frequent interruptions in the Hip
Hop mode.

Give them time;!.....

DAB, on the other hand, is rock solid - and by virtue of
having half the wavelength of FM, penetrates tunnels much further.. I
know that it has some fundamental quality limitations but they are
inconsequential in a car.


Like Mono?..


Can't say I'm bothered in the car. FM is more often mono than stereo
in the car anyway.


Blimey!, What stations do you listen to then?..

Around London? Any of 'em. The signal is entirely Rayleigh - there is
only multipath at street level. That means that while you are driving
the signal is rarely big enough for long enough to fire up the stereo
demux properly. In the absence of a huge DSP that can decompose
Eigenvectors, COFDM is about the best you can do to overcome this.

d

--
Pearce Consulting
http://www.pearce.uk.com

Simple systems with a HDD
 

tony sayer writes:

There is a system where crystal place relays Wrotham with something like
a 384 odd kHz offset there is a BBC engineering paper on it somewhere!..

It's here -- "THE CRYSTAL PALACE FM FILLER EXPERIMENT" (great title
for a sci-fi horror film, that):
http://downloads.bbc.co.uk/rd/pubs/reports/1996-06.pdf

--
Adam Sampson http://offog.org/

Simple systems with a HDD
 

On Wed, 25 Apr 2007 15:29:16 +0100, Adam Sampson
wrote:

tony sayer writes:

There is a system where crystal place relays Wrotham with something like
a 384 odd kHz offset there is a BBC engineering paper on it somewhere!..

It's here -- "THE CRYSTAL PALACE FM FILLER EXPERIMENT" (great title
for a sci-fi horror film, that):
http://downloads.bbc.co.uk/rd/pubs/reports/1996-06.pdf

Ah, that was clever. The offset is 304kHz, which is 16 times the
stereo beacon frequency so the sidebands intermesh and mutual
interference is minimal. It is a little like the concept behind the
4.433MHz colour subcarrier and its relationship with the luminance
signal in TV.

I said COFDM was the best answer, didn't I? And this is exactly that,
only using analogue signals (just drop the C bit).

d

--
Pearce Consulting
http://www.pearce.uk.com

Simple systems with a HDD
 

In article , Don Pearce
writes
On Wed, 25 Apr 2007 13:36:29 +0100, tony sayer
wrote:

In article , Don Pearce
writes
On Wed, 25 Apr 2007 11:54:26 +0100, tony sayer
wrote:

In article , Don Pearce
writes
On Wed, 25 Apr 2007 10:21:49 +0100, tony sayer
wrote:

In article , Dave Plowman (News)
writes
In article ,
tony sayer wrote:
Just local roads round Balham and area. One place I go for a coffee has
I'd say pretty high RF levels and that's a good test for the receiver
distortion. It's fairly close to CP - but tuning into Wrotham doesn't
cure the distortion. All using R4. Distortion on speech is easier to
assess than on most music.


I've got to go and collect a transmitter from Croydon before long I'll
have a wander round that area..

Right. Stop for a coffee at the cafe at the top of Streatham common - easy
parking there. See what R4 FM sounds like. I must say I've not tried the
new radio there yet, but all the others sound pretty horrid.


Noted....


Don't you use the CP relay the one offset from Wrotham?..

What are the frequencies of the various relays around here (London).
In theory for Radio 4, my best signal should be 93.5 but most of the
time I seem to be getting a much more solid signal below that - can't
remember what, but maybe 93.0.


There is a system where crystal place relays Wrotham with something like
a 384 odd kHz offset there is a BBC engineering paper on it somewhere!..

Really? I guess that just manifests itself as a frequency error in my
car radio then, it only manages 50kHz steps.

Apparently thats not supposed to happen. I'll see if I can remember
where it is, its on line somewhere!...


I'll be interested...


See its been found:)


I have to agree with Dave, though that driving around London FM is in
a constant state of swooshing, with frequent interruptions in the Hip
Hop mode.

Give them time;!.....

DAB, on the other hand, is rock solid - and by virtue of
having half the wavelength of FM, penetrates tunnels much further.. I
know that it has some fundamental quality limitations but they are
inconsequential in a car.


Like Mono?..


Can't say I'm bothered in the car. FM is more often mono than stereo
in the car anyway.


Blimey!, What stations do you listen to then?..

Around London? Any of 'em. The signal is entirely Rayleigh - there is
only multipath at street level. That means that while you are driving
the signal is rarely big enough for long enough to fire up the stereo
demux properly. In the absence of a huge DSP that can decompose
Eigenvectors, COFDM is about the best you can do to overcome this.

d


Bad as that eh?, long time since I've been down that way...
--
Tony Sayer