North London and clashing signals

On 09/06/2010 08:57, charles wrote:

Once upon a time mf radios had a choice of if depending on which country it
was to be used in. 455 (or 450) is not too good in the UK since 910 is one
of our main frequencies.

Yes, I remember the whistle on my grandmother's Hacker radio, when it
was tuned to (at the time) R4 Brookmans Park on 908kHz.



--
Mark
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"Ivan" wrote in message
news:[email protected]cane...

"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

455 kHz the local oscillator frequency for many MW radios.

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

As Charles says, crap receiver design/quality.


Even Sony = 'made in China'?

You could try to get hold of an "antique" pocket radio, manufactured in the
60s or 70s, or at least before about 1985 (before the days of 455 kHz
ceramic filters). These usually have an IF (intermediate frequency) of 470
or 468 kHz, so the image of Gold will appear at 612 or 608 kHz instead of
648 kHz, and you should be able to receive BBC World Service without image
channel interference from Gold.

The reason you have the problem in the first place is that you are unusually
close to the Gold transmitter. Your signal from Gold is stronger than an
average radio is designed to cope with.

That combined with the fact that the BBC World Service frequency was not
designed for reception in the UK. If it had been then its signal would be
stronger, and it probably would not be using a frequency 2 x IF away that
from another licensed station in the same area could be subject to image
channel interference , as you are experiencing.

On 09/06/2010 09:42, Stephen wrote:

That combined with the fact that the BBC World Service frequency was not
designed for reception in the UK. If it had been then its signal would be
stronger, and it probably would not be using a frequency 2 x IF away that
from another licensed station in the same area could be subject to image
channel interference , as you are experiencing.

True, but pre 1978 647kHz was used for BBC Radio 3 from Daventry, and
1546 kHz was used for local radio (London, Bristol, Cleveland,
Sheffield, Liverpool). In fact pre 1972, I think 1546 was used as a fill
in service for R3 is some areas ?

(Nov 78 647 became 648, and 1546 became 1548 for the '9kHz' MF band plan
scheme)


--
Mark
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In article ,
Mark Carver wrote:
On 09/06/2010 09:42, Stephen wrote:

That combined with the fact that the BBC World Service frequency was
not designed for reception in the UK. If it had been then its signal
would be stronger, and it probably would not be using a frequency 2 x
IF away that from another licensed station in the same area could be
subject to image channel interference , as you are experiencing.

True, but pre 1978 647kHz was used for BBC Radio 3 from Daventry, and
1546 kHz was used for local radio (London, Bristol, Cleveland,
Sheffield, Liverpool). In fact pre 1972, I think 1546 was used as a fill
in service for R3 is some areas ?

(Nov 78 647 became 648, and 1546 became 1548 for the '9kHz' MF band plan
scheme)

it alwasy was a "9kHz" plan in 1978 it became a "divide by 9" plan

--
From KT24

Using a RISC OS computer running v5.16

On 09/06/2010 12:29, charles wrote:

(Nov 78 647 became 648, and 1546 became 1548 for the '9kHz' MF band plan
scheme)

it alwasy was a "9kHz" plan in 1978 it became a "divide by 9" plan

It couldn't have been 9kHz spacing across the whole MF band, because
1546kHz was increased by 2kHz, while most of the other allocations only
increased by 1 kHz ?



--
Mark
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http://www.paras.org.uk/

On Jun 9, 6:22*am, Mark Carver wrote:
On 09/06/2010 00:37, Ivan wrote:



"Mark Carver" wrote in message
Even Sony = 'made in China'?

Well, I've got the reasonably 'up market' and 20 year old, made in
Japan, ICF-SW7600. That performs very well on the MF and HF bands, but
the FM section (that tunes from 76.0 MHz to 108.0), is easily
overloaded, and nasty IF images pop up from stations that have
relatively moderate RF levels. Someone told me, the FM section is just
'chucked in' afterthought. A shame because it lets the receiver down.

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

http://www.paras.org.uk/

I have an ICF-M50RDS and the FM selectivity is very poor. Radio Hallam
from 2km away is on top of every other station.

Bill

"Mark Carver" wrote in message
...
On 09/06/2010 09:42, Stephen wrote:

That combined with the fact that the BBC World Service frequency was not
designed for reception in the UK. If it had been then its signal would be
stronger, and it probably would not be using a frequency 2 x IF away that
from another licensed station in the same area could be subject to image
channel interference , as you are experiencing.

True, but pre 1978 647kHz was used for BBC Radio 3 from Daventry, and
1546 kHz was used for local radio (London, Bristol, Cleveland, Sheffield,
Liverpool). In fact pre 1972, I think 1546 was used as a fill in service
for R3 is some areas ?

(Nov 78 647 became 648, and 1546 became 1548 for the '9kHz' MF band plan
scheme)


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

http://www.paras.org.uk/

Pre1972 it would not have mattered if your 1546 transmitter prouced image
channel interference on 647, because they were carrying the same programme
and you could simply retune to the local relay of Radio 3 on 1546, which
would have been the one you were meant to use anyway.

On Wednesday, June 9th, 2010 at 06:22:26h +0100, Mark Carver wrote:

Well, I've got the reasonably 'up market' and 20 year old, made in
Japan, ICF-SW7600. That performs very well on the MF and HF bands, but
the FM section (that tunes from 76.0 MHz to 108.0), is easily
overloaded, and nasty IF images pop up from stations that have
relatively moderate RF levels. Someone told me, the FM section is just
'chucked in' afterthought. A shame because it lets the receiver down.

The best portable VHF FM receivers were the top of the range Grundig models
of the 1980s.

Since then, portable VHF FM receiver quality has been downhill.

In article ,
J G Miller wrote:
On Wednesday, June 9th, 2010 at 06:22:26h +0100, Mark Carver wrote:

Well, I've got the reasonably 'up market' and 20 year old, made in
Japan, ICF-SW7600. That performs very well on the MF and HF bands, but
the FM section (that tunes from 76.0 MHz to 108.0), is easily
overloaded, and nasty IF images pop up from stations that have
relatively moderate RF levels. Someone told me, the FM section is just
'chucked in' afterthought. A shame because it lets the receiver down.

The best portable VHF FM receivers were the top of the range Grundig
models of the 1980s.

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.

Since then, portable VHF FM receiver quality has been downhill.

you might well be right.

--
From KT24

Using a RISC OS computer running v5.16

Mark Carver wrote:
On 09/06/2010 08:57, charles wrote:

Once upon a time mf radios had a choice of if depending on which
country it
was to be used in. 455 (or 450) is not too good in the UK since 910 is
one
of our main frequencies.

Yes, I remember the whistle on my grandmother's Hacker radio, when it
was tuned to (at the time) R4 Brookmans Park on 908kHz.



All receivers of far eastern design AFAIK (and that probably includes a
lot European badged receivers of far eastern origin) use an IF of 455kHz.
--

Terry