North London and clashing signals

Mark Carver wrote:
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 ?


A few channels at the very top end of the MW band had 8kHz spacing but
all the rest were 9kHz.
--

Terry

Johnny B Good wrote:
The message
from Mark Carver contains these words:

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.

John's reply regarding the frequency was slightly ambiguous. I thought
he was referring to Gold's frequency being 648KHz (with BBC WS on
1548KHz). It would have to be this way round for the IF image mechanism
to be responsible for the interference from BBC WS on Gold since it has
been standard practice for the LO to be tuned above the incoming MW
signal[1].

A definitive indicator for image frequency interference is the classic
rapid pitch change of the beat frequency as you slowly tune across the
channel occupied by the wanted broadcast.

A better design of radio, in this context, would either be a double
conversion type or an extra tuned circuit (amplified or not) on the
input stage to the mixer requiring a three gang tuning capacitor. These
are features that simply don't appear on cheap LW/MW radios (not even if
the have a VHF tuner).

One "Quick Fix" in this particular case, would be to retune the IF
stages up or down by 4 or 5KHz if the radio is a basic analogue tuned
design (a 5KHz shift would displace the unwanted image by 10KHz). Such
tuning is well within the adjustment range of the IF coils but you might
upset any 'stagger tuning' used to approximate a flat bandpass filter
effect.


The chances of the OP having radios with tunable IF transformers are
exceedingly slim - ceramic filters have ruled the roost for a very long
time!

--

Terry

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.

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

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.

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.

I preferred the Tandberg TP41. Perhaps because to me it simply gave better
sound than the Grundigs I tried. (First colour TV was Grundig, though!)

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

I fear that tends to apply to fancy 'hi fi' tuners as well as portables.
For many years I was pleased I'd got a Yamaha CT7000 when I did! A decade
or so later there were no new FM tuners that could match it or the other
'super tuners' of the period it was made.

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

On Jun 10, 9:17*am, Mark Carver wrote:
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.

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

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.

Bill

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'

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

In article , Jim Lesurf
scribeth thus
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.

I preferred the Tandberg TP41. Perhaps because to me it simply gave better
sound than the Grundigs I tried. (First colour TV was Grundig, though!)

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

I fear that tends to apply to fancy 'hi fi' tuners as well as portables.
For many years I was pleased I'd got a Yamaha CT7000 when I did! A decade
or so later there were no new FM tuners that could match it or the other
'super tuners' of the period it was made.

Ever tried an Audiolab T8000 ?...

well from the 90's ..

Slainte,

Jim


--
Tony Sayer

" wrote in
message
...
On Jun 10, 9:17 am, Mark Carver
wrote:
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.

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

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.

Bill



Sure that ain't GPS with the rear (saloon) or rear side (estate)
windows actually doing the aerialing?


--
Woody

harrogate three at ntlworld dot com

Woody wrote:

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.

Sure that ain't GPS with the rear (saloon) or rear side (estate)
windows actually doing the aerialing?

My parents have an 2007 Volvo, it also has the lump, and I'm equally intrigued
by it. It seems to contain the car radio's aerial, I can influence the
received signal by putting my hand near it.



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

www.paras.org.uk

Terry Casey wrote:
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.

I'm surprised, the inerds were very 'british', big friendly looking
components, I'm sure some were Mullard, ran off two PP9s, and it had the feel
as if it was built from a Henry's Radio kit :-)

Can find a ref on the web, a bit like this set, but without FM:-

http://www.hacker-radio.fotopic.net/p40653995.html

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

www.paras.org.uk