North London and clashing signals

"Mark Carver" wrote in message
...
On 08/06/2010 23:19, Brian Gregory [UK] wrote:
"john wrote in message


Gold is on 1548kHz in London, right?

There's no BBC world service anywhere near that as far as I know.

Capital Gold 1548 kHz

BBC World Service 648 kHz

1548-648= 900kHz

900/2= 455 kHz

I make it 450kHz.

But 455kHz might be near enough for it to be a problem.

Also some digitally tuned radios do use a 450kHz IF.


455 kHz the local oscillator frequency for many MW radios.

No, it's the IF frequency.


Therefore BBC World is appearing 'on top of' Capital Gold as a 2xIF image.

As Charles says, crap receiver design/quality.

This always happens to some extent with most designs but normally isn't a
big problem except when the unwanted signal is very strong.

I'm surprised the BBC WS on 648kHz is strong enough to cause this problem in
London. It's appalingly weak here in Reading since they introduced the
latest directinal antennas to beam 648kHz towards europe.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Jim Lesurf" wrote in message
...
In article
,
wrote:
On Jun 10, 9:17 am, Mark Carver wrote:


I'd say you're right, though FM car radio receiver quality continues
to generally improve. The radio in my 2008 Peugeot is superb. It's
very sensitive, and incredibly selective, has no difficulty receiving
stations that are only 100kHz away from an 'unwanted' station of
moderate strength. The level of audio 'splashover' is minimal.

I can't understand how the radio in Hil's Volvo works as well as it
does, considering the aerial is just a small plastic lump on the roof.

Perhaps it is actually coupling to the car bodywork and using that as the
actual antenna. Mobile phones may well essentially be using the body of
the
person holding them as part of their 'antenna'

You need two parts to any wire or rod antenna. The car body is already an
important part of the normal car rod antenna system, it forms a counterpoise
or groundplane. If you try to use the car body as the antenna there is
nothing left to be a couterpoise.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

In message , "Brian Gregory
[UK]" writes
"Mark Carver" wrote in message
...
On 08/06/2010 23:19, Brian Gregory [UK] wrote:
"john wrote in message


Gold is on 1548kHz in London, right?

There's no BBC world service anywhere near that as far as I know.

Capital Gold 1548 kHz

BBC World Service 648 kHz

1548-648= 900kHz

900/2= 455 kHz

I make it 450kHz.

But 455kHz might be near enough for it to be a problem.

Also some digitally tuned radios do use a 450kHz IF.


455 kHz the local oscillator frequency for many MW radios.

No, it's the IF frequency.


Therefore BBC World is appearing 'on top of' Capital Gold as a 2xIF image.

As Charles says, crap receiver design/quality.

This always happens to some extent with most designs but normally isn't a
big problem except when the unwanted signal is very strong.

I'm surprised the BBC WS on 648kHz is strong enough to cause this problem in
London. It's appalingly weak here in Reading since they introduced the
latest directinal antennas to beam 648kHz towards europe.

The initial diagnosis was amended some time. However, I'm not sure that
the revised one was correct either. Without going back to find it, I
believe that, somewhere in the works, it involved the second harmonic of
the WS. However, it would have to be very strong for this to happen.

Mind you, although the WS may be appallingly weak in Reading, while not
strong, it's not too bad a signal in the Beaconsfield (M40 J2) area. If
they are now using an even more super-duper beamed signal, I suppose it
could be a lot stronger in London. With LBC, on 1151kHz, I'm in an
extremely sharp, deep null, but if I drive less than a mile eastward
towards London, the signal rises tremendously, and then continues to
rise all the way in. Maybe the WS does something similar.
--
Ian

In article , Brian Gregory
[UK] wrote:
"Jim Lesurf" wrote in message
...
In article
,
wrote:
On Jun 10, 9:17 am, Mark Carver wrote:


I'd say you're right, though FM car radio receiver quality
continues to generally improve. The radio in my 2008 Peugeot is
superb. It's very sensitive, and incredibly selective, has no
difficulty receiving stations that are only 100kHz away from an
'unwanted' station of moderate strength. The level of audio
'splashover' is minimal.

I can't understand how the radio in Hil's Volvo works as well as it
does, considering the aerial is just a small plastic lump on the roof.

Perhaps it is actually coupling to the car bodywork and using that as
the actual antenna. Mobile phones may well essentially be using the
body of the person holding them as part of their 'antenna'

You need two parts to any wire or rod antenna.

Yes. They do need physical lengths that are non-zero. That is essentially
what makes them a 'wire' or a 'rod' of some other definable shape. :-)

The car body is already an important part of the normal car rod antenna
system, it forms a counterpoise or groundplane.

Not ideally worded for this case, perhaps that is what is leading you to
into the confusion inherent in your next assertion...

If you try to use the car body as the antenna there is nothing left to
be a couterpoise.

The problem with applying your simplified assertion in this case is that a
"car body" has dimensions that are *not* considerably smaller than the
relevant wavelength. So two different locations around/within that volume
can indeed have E and H fields between them. Thus can be used as an antenna
if suitably coupled/matched. Perhaps you missed the significance of the
words "part of" in the above since your own earlier statements essentially
agree with what I wrote.

Or are you claiming that a mobile phone can't work, either, since they
don't have a 'rod' or 'wire' clearly poking out of them? :-)

ahem BTW your 'counterpoise' and 'groundplane' approach may not help you
much when it comes to dealing with loop antennas/couplers, either. ;-

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Ian Jackson wrote:
In message , "Brian Gregory
[UK]" writes
"Mark Carver" wrote in message
...
On 08/06/2010 23:19, Brian Gregory [UK] wrote:
"john wrote in message


Gold is on 1548kHz in London, right?

There's no BBC world service anywhere near that as far as I know.

Capital Gold 1548 kHz

BBC World Service 648 kHz

1548-648= 900kHz

900/2= 455 kHz

I make it 450kHz.

But 455kHz might be near enough for it to be a problem.

Also some digitally tuned radios do use a 450kHz IF.


455 kHz the local oscillator frequency for many MW radios.

No, it's the IF frequency.


Therefore BBC World is appearing 'on top of' Capital Gold as a 2xIF
image.

As Charles says, crap receiver design/quality.

This always happens to some extent with most designs but normally isn't a
big problem except when the unwanted signal is very strong.

I'm surprised the BBC WS on 648kHz is strong enough to cause this
problem in
London. It's appalingly weak here in Reading since they introduced the
latest directinal antennas to beam 648kHz towards europe.

The initial diagnosis was amended some time. However, I'm not sure that
the revised one was correct either. Without going back to find it, I
believe that, somewhere in the works, it involved the second harmonic of
the WS. However, it would have to be very strong for this to happen.

Mind you, although the WS may be appallingly weak in Reading, while not
strong, it's not too bad a signal in the Beaconsfield (M40 J2) area. If
they are now using an even more super-duper beamed signal, I suppose it
could be a lot stronger in London. With LBC, on 1151kHz, I'm in an
extremely sharp, deep null, but if I drive less than a mile eastward
towards London, the signal rises tremendously, and then continues to
rise all the way in. Maybe the WS does something similar.

I doubt it. The reason for the null you are experiencing from Saffron
Green is that it was designed deliberately that way. I can't remember if
there was more than one - one of the old IBA Technical Reviews described
it in detail - but it/they were 'aimed' at other ILR sites using the
sdame frequency. Try drawing a line on a map and see what you come up with!

Orford Ness, on the other hand, is designed to radiate as little of its
power as possible to the UK - there would be no point in designing in a
specific sharp null.

--

Terry

Terry Casey wrote:

I doubt it. The reason for the null you are experiencing from Saffron
Green is that it was designed deliberately that way. I can't remember if
there was more than one - one of the old IBA Technical Reviews described
it in detail - but it/they were 'aimed' at other ILR sites using the
sdame frequency. Try drawing a line on a map and see what you come up with!

IBA Tech Review 5 and 14.

From Tech Review 14 Page 47:-

The Saffron Green nulls are,

Capital 1548kHz:-

Bristol
Liverpool
Sheffield
Edinburgh
Teesside

LBC 1152 kHz

Plymouth
Birmingham
Manchester
Glasgow
Newcastle


--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

In message [email protected], Terry Casey
writes
Ian Jackson wrote:
In message , "Brian
Gregory [UK]" writes
"Mark Carver" wrote in message
...
On 08/06/2010 23:19, Brian Gregory [UK] wrote:
"john wrote in message


Gold is on 1548kHz in London, right?

There's no BBC world service anywhere near that as far as I know.

Capital Gold 1548 kHz

BBC World Service 648 kHz

1548-648= 900kHz

900/2= 455 kHz

I make it 450kHz.

But 455kHz might be near enough for it to be a problem.

Also some digitally tuned radios do use a 450kHz IF.


455 kHz the local oscillator frequency for many MW radios.

No, it's the IF frequency.


Therefore BBC World is appearing 'on top of' Capital Gold as a 2xIF
image.

As Charles says, crap receiver design/quality.

This always happens to some extent with most designs but normally isn't a
big problem except when the unwanted signal is very strong.

I'm surprised the BBC WS on 648kHz is strong enough to cause this
problem in
London. It's appalingly weak here in Reading since they introduced the
latest directinal antennas to beam 648kHz towards europe.

The initial diagnosis was amended some time. However, I'm not sure
that the revised one was correct either. Without going back to find
it, I believe that, somewhere in the works, it involved the second
harmonic of the WS. However, it would have to be very strong for this
to happen.
Mind you, although the WS may be appallingly weak in Reading, while
not strong, it's not too bad a signal in the Beaconsfield (M40 J2)
area. If they are now using an even more super-duper beamed signal, I
suppose it could be a lot stronger in London. With LBC, on 1151kHz,
I'm in an extremely sharp, deep null, but if I drive less than a mile
eastward towards London, the signal rises tremendously, and then
continues to rise all the way in. Maybe the WS does something similar.

I doubt it. The reason for the null you are experiencing from Saffron
Green is that it was designed deliberately that way. I can't remember
if there was more than one - one of the old IBA Technical Reviews
described it in detail - but it/they were 'aimed' at other ILR sites
using the sdame frequency. Try drawing a line on a map and see what you
come up with!

Orford Ness, on the other hand, is designed to radiate as little of its
power as possible to the UK - there would be no point in designing in a
specific sharp null.

Oh, I know that the null is specially designed into the radiation
pattern of the LBC arterial. Without checking, I recall that it was
aimed at Bristol, to avoid interfering with Radio Bristol*. However, the
main lobe of the LBC aerial (a phased 4-mast beam) puts a thumping great
signal into London. Unless things have changed, there is little trouble
receiving it in Brighton and, at night, in Rouen in France. Go north
past the aerial, and reception fairly quickly gets a bit iffy in places.

*I was sure that is was Bristol. However, I see from Mark Carver's post
that it is Plymouth. Close, but no cigar!

I haven't listened lately to the BBC WS in the London area, but I expect
that it will be stronger than it is here (about 30 miles west of
London), and that it will get progressively stronger as you head further
eastwards towards the North Sea. But, in London, I doubt if it is
literally overpoweringly strong. I can't see it causing a self-generated
2nd harmonic (1296kHz) in a receiver, whose aerial input is tuned to
1548kHz. However, 'something' must be causing the problem.
--
Ian

"Jim Lesurf" wrote in message
...
In article , Brian Gregory
[UK] wrote:
"Jim Lesurf" wrote in message
...
In article
,
wrote:
On Jun 10, 9:17 am, Mark Carver wrote:


I'd say you're right, though FM car radio receiver quality
continues to generally improve. The radio in my 2008 Peugeot is
superb. It's very sensitive, and incredibly selective, has no
difficulty receiving stations that are only 100kHz away from an
'unwanted' station of moderate strength. The level of audio
'splashover' is minimal.

I can't understand how the radio in Hil's Volvo works as well as it
does, considering the aerial is just a small plastic lump on the roof.

Perhaps it is actually coupling to the car bodywork and using that as
the actual antenna. Mobile phones may well essentially be using the
body of the person holding them as part of their 'antenna'

You need two parts to any wire or rod antenna.

Yes. They do need physical lengths that are non-zero. That is essentially
what makes them a 'wire' or a 'rod' of some other definable shape. :-)

The car body is already an important part of the normal car rod antenna
system, it forms a counterpoise or groundplane.

Not ideally worded for this case, perhaps that is what is leading you to
into the confusion inherent in your next assertion...

If you try to use the car body as the antenna there is nothing left to
be a couterpoise.

The problem with applying your simplified assertion in this case is that a
"car body" has dimensions that are *not* considerably smaller than the
relevant wavelength. So two different locations around/within that volume
can indeed have E and H fields between them. Thus can be used as an
antenna
if suitably coupled/matched. Perhaps you missed the significance of the
words "part of" in the above since your own earlier statements essentially
agree with what I wrote.

Or are you claiming that a mobile phone can't work, either, since they
don't have a 'rod' or 'wire' clearly poking out of them? :-)

I must admit I hadn't thought of the possibility that, say, the roof panel
might be electrically isolated from the rest of the body and I agree that
using that would work fine.


ahem BTW your 'counterpoise' and 'groundplane' approach may not help you
much when it comes to dealing with loop antennas/couplers, either. ;-


Agreed.
I meant the phrase "wire of rod" to exclude other types my assertions didn't
apply to, but I agree it's a little unclear.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Brian Gregory [UK]" wrote in message
...
"Mark Carver" wrote in message
...
On 08/06/2010 23:19, Brian Gregory [UK] wrote:
"john wrote in message


Gold is on 1548kHz in London, right?

There's no BBC world service anywhere near that as far as I know.

Capital Gold 1548 kHz

BBC World Service 648 kHz

1548-648= 900kHz

900/2= 455 kHz

I make it 450kHz.

But 455kHz might be near enough for it to be a problem.

Also some digitally tuned radios do use a 450kHz IF.


455 kHz the local oscillator frequency for many MW radios.

No, it's the IF frequency.


Therefore BBC World is appearing 'on top of' Capital Gold as a 2xIF
image.

As Charles says, crap receiver design/quality.

This always happens to some extent with most designs but normally isn't a
big problem except when the unwanted signal is very strong.

I'm surprised the BBC WS on 648kHz is strong enough to cause this problem
in London. It's appalingly weak here in Reading since they introduced the
latest directinal antennas to beam 648kHz towards europe.

Actually I've just looked through the rest of the thread been nudged into
realizing that it's not that way round. Any normal single conversion
receiver will have problems with strong signals from twice it's IF *above*
the frequency it's tuned to.

I wonder if the problem could be that the OP is actually tuning to around
648kHz when he wants to hear 1548kHz and getting enough 1548kHz through
(because it's really strong) for him to think he's tuning correctly.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

On Wed, 09 Jun 2010 17:15:31 +0100, charles
wrote:

There were also those made by Hacker (who disappeared) and B&O. I had one
of the latter after exhaustive testing in a reception hole.

Mother has a Roberts which isn't too shabby.

I miss my Hacker. It died during a strange incident. The neighbours
upstairs clearly heard me come in, listen to the radio for a bit and
go to bed, then get up early in the morning.

Actually I was at my girlfriend's, and when I came home not only had
some total stranger slept in my bed, he had vomited all over the poor
Hacker.

We never found out who it was.