No DAB reception in cars near BBC Television Centre!

Silk wrote:


Careful about using the word guarantee. :-)

Someone might say, that if you have guaranteed it, then you need to
prove it. The only way to do that would involve a trip to London,
which would be a long way for you.

It's not that far. I regularly travel a lot further than that.

Well if you are in the area it might be an interesting thing to try. The
thing is, even the best possible receiver will fail if the signal
becomes weak enough.

Perhaps that dead spot is only enough to affect lower quality receivers,
or then again, it might just happen to be so bad that even good
receiving equipment will fail. This can happen.

Richard E.

Richard Evans wrote:

Well if you are in the area it might be an interesting thing to try. The
thing is, even the best possible receiver will fail if the signal
becomes weak enough.

I think this particular story is an urban myth. I remember it from a few
years ago. It would make a good story for a radio station not to be
receivable outside the building that it's broadcast from.

In message , Silk writes
Richard Evans wrote:

Well if you are in the area it might be an interesting thing to try.
The thing is, even the best possible receiver will fail if the signal
becomes weak enough.

I think this particular story is an urban myth. I remember it from a
few years ago. It would make a good story for a radio station not to be
receivable outside the building that it's broadcast from.

Well, I understand that reception very close to certain TV transmitters
in urban areas (eg Crystal Palace) would be very poor if is was not for
the fact that that they deliberately put a little squirt of RF down at a
very steep angle (compared with the usual, say, 3 to 5 degrees of the
rest of the aerial).
--
Ian

On Mon, 06 Jul 2009 02:48:37 +0100, Richard Evans
wrote:

hwh wrote:


It depends. The signal in London is not good enough for many people. So
either you turn up the power or you put in more transmitters. It all
comes down to money. In Australia they started using up to 50 kW.

I noticed on the Australian coverage maps, they seem to use just one TX
site for each city. I suppose they can get away with that, because the
cities are far enough apart, so that they can use high power with out
interfering with each other.


Australia is a completely different case. Long distances between
cities, and no adjacent countries to negotiate with.

On Sun, 05 Jul 2009 13:28:11 +0200, hwh
wrote:

charles wrote:
The range of a powerful signal can be limited by using a technique
called 'downtilt'. When a large aerial is used, it can be used to focus
the signal on a point not too far away from the site.

Beam tilt is an extremely useful technique where coverage has be
greatly restricted to enable intensive frequency re-use, e.g. for
cellular radio. For broadcasting you will usually find it only where a
fill-in relay is beaming down into a 'hole', rather than on high power
wide area coverage sites.

I think you will find that nearly all uhf tv transmitters have beam tilt.
Even main stations

And FM stations as well. If they would transmit horizontally the signal
would simply pass over everyone's heads.


Er yes - that basic point has not escaped me during my years of
service planning As a starting point you will of course tailor
both the HRP and VRP to suit the required service area.

But I am responding to the suggestion that DAB coverage can be
substantially improved by simply upping the power and tilting the
beam. As others have said this cannot fill in coverage holes which
will be many dB down. For these areas you either build relay sites or
provide an alternative service such as cable or satellite - and these
are inappropriate for a service like DAB which is intended for mobile
or portable reception.

I also wanted to make the point that you cannot de-couple the service
range of a transmitter from its interference range.

In article ,
Richard Evans wrote:
Perhaps that dead spot is only enough to affect lower quality receivers,
or then again, it might just happen to be so bad that even good
receiving equipment will fail. This can happen.

As you may well know, DAB receivers have a separate input for the DAB
aerial. When I first got mine I used a pro combiner to use the AM/FM
telescopic wing mount aerial and the results were poor. The roof one I
replaced it with is two units in the one aerial - with two pre amps. The
DAB one uses 'T Power' to it - the AM FM a separate downlead with a
separate 12 volt supply to that. So not an easy installation as the
headlining and windscreen pillar trims had to come out. The usual DAB
window aerials are useless too.

--
*To steal ideas from *one* person is plagiarism; from many, research*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Silk wrote:
I think this particular story is an urban myth. I remember it from a few
years ago. It would make a good story for a radio station not to be
receivable outside the building that it's broadcast from.

Reminds me of Capital Radio when they started out at Euston...

--
* I like you. You remind me of when I was young and stupid

Dave Plowman London SW
To e-mail, change noise into sound.

On Mon, 06 Jul 2009 10:40:10 +0100
"Dave Plowman (News)" wrote:


In article ,
Richard Evans wrote:
Perhaps that dead spot is only enough to affect lower quality receivers,
or then again, it might just happen to be so bad that even good
receiving equipment will fail. This can happen.

As you may well know, DAB receivers have a separate input for the DAB
aerial. When I first got mine I used a pro combiner to use the AM/FM
telescopic wing mount aerial and the results were poor. The roof one I

That surprises me. The low 200mhz frequency used by DAB is near as makes no
difference twice the frequency of FM stations so a standard half wave FM
antenna should become a full wave DAB antenna and in theory should work
very well.

B2003

In article , wrote:
On Mon, 06 Jul 2009 10:40:10 +0100 "Dave Plowman (News)"
wrote:


In article , Richard Evans
wrote:
Perhaps that dead spot is only enough to affect lower quality
receivers, or then again, it might just happen to be so bad that even
good receiving equipment will fail. This can happen.

As you may well know, DAB receivers have a separate input for the DAB
aerial. When I first got mine I used a pro combiner to use the AM/FM
telescopic wing mount aerial and the results were poor. The roof one I

That surprises me. The low 200mhz frequency used by DAB is near as makes
no difference twice the frequency of FM stations so a standard half wave
FM antenna should become a full wave DAB antenna and in theory should
work very well.

but it might be mounted a half DAB wavelength away from the windscreen
pillar

--
From KT24

Using a RISC OS computer running v5.11

In article ,
wrote:
On Mon, 06 Jul 2009 10:40:10 +0100
"Dave Plowman (News)" wrote:


In article ,
Richard Evans wrote:
Perhaps that dead spot is only enough to affect lower quality receivers,
or then again, it might just happen to be so bad that even good
receiving equipment will fail. This can happen.

As you may well know, DAB receivers have a separate input for the DAB
aerial. When I first got mine I used a pro combiner to use the AM/FM
telescopic wing mount aerial and the results were poor. The roof one I

That surprises me. The low 200mhz frequency used by DAB is near as makes
no difference twice the frequency of FM stations so a standard half wave
FM antenna should become a full wave DAB antenna and in theory should
work very well.

Yes - I'd heard that theory before. Although turning my FM aerial vertical
at home didn't seem to work too well for DAB. Nor strangely for FM either.
It's a 4 element J-Beam.
B2003

--
*The severity of the itch is proportional to the reach *

Dave Plowman London SW
To e-mail, change noise into sound.