OK - so I got the co-axial to F type connector and reception on Rado 3 is 
worse than with the 18 in single wire aerial supplied. So I tried it without 
any aerial at all - even better!!!

Gordon

In article <g8j8fi$9ev$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
MacPherson  scribeth thus
>OK - so I got the co-axial to F type connector and reception on Rado 3 is 
>worse than with the 18 in single wire aerial supplied. So I tried it without 
>any aerial at all - even better!!!
>
>Gordon 
>
>

If your serious about FM reception why don't you get a three element
Yagi or similar and put it up in your loft space or outside somewhere,
rather than faff around with rather iffy indoor things?...
-- 
Tony Sayer

"tony sayer"  wrote in message 
news:CLRDcnDSEVrIFwS6@bancom.co.uk...
> In article <g8j8fi$9ev$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
> MacPherson  scribeth thus
>>OK - so I got the co-axial to F type connector and reception on Rado 3 is
>>worse than with the 18 in single wire aerial supplied. So I tried it 
>>without
>>any aerial at all - even better!!!
>>
>>Gordon
>>
>>
>
> If your serious about FM reception why don't you get a three element
> Yagi or similar and put it up in your loft space or outside somewhere,
> rather than faff around with rather iffy indoor things?...
> -- 
> Tony Sayer
>
>
I do have this for my Hi-Fi listening on a completely different set up. The 
one I am talking about sits in the kitchen,

In article <g8k0uc$imc$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
MacPherson  scribeth thus
>
>"tony sayer"  wrote in message 
>news:CLRDcnDSEVrIFwS6@bancom.co.uk...
>> In article <g8j8fi$9ev$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
>> MacPherson  scribeth thus
>>>OK - so I got the co-axial to F type connector and reception on Rado 3 is
>>>worse than with the 18 in single wire aerial supplied. So I tried it 
>>>without
>>>any aerial at all - even better!!!
>>>
>>>Gordon
>>>
>>>
>>
>> If your serious about FM reception why don't you get a three element
>> Yagi or similar and put it up in your loft space or outside somewhere,
>> rather than faff around with rather iffy indoor things?...
>> -- 
>> Tony Sayer
>>
>>
>I do have this for my Hi-Fi listening on a completely different set up. The 
>one I am talking about sits in the kitchen, 
>
>
Right..

Pains me to say it but have you tried DAB?..
-- 
Tony Sayer

tony sayer wrote:
> In article <g8k0uc$imc$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
> MacPherson  scribeth thus
>
>> I do have this for my Hi-Fi listening on a completely different set up. The 
>> one I am talking about sits in the kitchen, 

> Right..

The OP is very close to the Tx at Beckley. (46kW at about 5 miles). I'm 
beginning to wonder if his problem is actually multipath reception rather than 
low signal ? There's all those car factory buildings in Cowley to bounce the 
signal about. A yagi outside, perhaps with an attenuator might be the only 
viable solution ?

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

"tony sayer"  wrote in message 
news:VCiWubBe8crIFwB8@bancom.co.uk...
> In article <g8k0uc$imc$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
> MacPherson  scribeth thus
>>
>>"tony sayer"  wrote in message
>>news:CLRDcnDSEVrIFwS6@bancom.co.uk...
>>> In article <g8j8fi$9ev$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
>>> MacPherson  scribeth thus
>>>>OK - so I got the co-axial to F type connector and reception on Rado 3 
>>>>is
>>>>worse than with the 18 in single wire aerial supplied. So I tried it
>>>>without
>>>>any aerial at all - even better!!!
>>>>
>>>>Gordon
>>>>
>>>>
>>>
>>> If your serious about FM reception why don't you get a three element
>>> Yagi or similar and put it up in your loft space or outside somewhere,
>>> rather than faff around with rather iffy indoor things?...
>>> -- 
>>> Tony Sayer
>>>
>>>
>>I do have this for my Hi-Fi listening on a completely different set up. 
>>The
>>one I am talking about sits in the kitchen,
>>
>>
> Right..
>
> Pains me to say it but have you tried DAB?..
> -- 
> Tony Sayer
>

DAB is fine in bathroom and bedroom - it is the excellent sound quality of 
the Creative receiver (and it plays CDs) that I want to preserve.

Gordon

Well, cannot say I'm surprised really. Welcome to the joys of indoor 
reception.

I imagine  just dangling a screwdriver out the back  might also give better 
results.

It sounds to me  as if you have plenty of signal, but its of course bouncing 
around in the  building and this is why you get all sorts of strange 
effects.

I'm afraid you will need to make sure the signal from the aerial is much 
greater than stray pick up in the room as otherwise you will get 
add/cancellation effects  like this. Hence our comments about outside or 
loft aerials. Very few  radios are screened much internally, and random pick 
up on the mains etc, adds to the equation.


Brian

-- 
Brian Gaff....Note, this account does not accept Bcc: email.
 graphics are great, but the blind can't hear them
Email: briang1@blueyonder.co.uk
______________________________________________________________________________________________________________


"Gordon MacPherson"  wrote in message 
news:g8j8fi$9ev$1@frank-exchange-of-views.oucs.ox.ac.uk...
> OK - so I got the co-axial to F type connector and reception on Rado 3 is 
> worse than with the 18 in single wire aerial supplied. So I tried it 
> without any aerial at all - even better!!!
>
> Gordon
>

Well, how about an aerial switch and a short length of coax to your kitchen? 
No way will an indoor aerial  give good reception unless you are very very 
lucky.

Its the nature of the beast.

Brian

-- 
Brian Gaff....Note, this account does not accept Bcc: email.
 graphics are great, but the blind can't hear them
Email: briang1@blueyonder.co.uk
______________________________________________________________________________________________________________


"Gordon MacPherson"  wrote in message 
news:g8k0uc$imc$1@frank-exchange-of-views.oucs.ox.ac.uk...
>
> "tony sayer"  wrote in message 
> news:CLRDcnDSEVrIFwS6@bancom.co.uk...
>> In article <g8j8fi$9ev$1@frank-exchange-of-views.oucs.ox.ac.uk>, Gordon
>> MacPherson  scribeth thus
>>>OK - so I got the co-axial to F type connector and reception on Rado 3 is
>>>worse than with the 18 in single wire aerial supplied. So I tried it 
>>>without
>>>any aerial at all - even better!!!
>>>
>>>Gordon
>>>
>>>
>>
>> If your serious about FM reception why don't you get a three element
>> Yagi or similar and put it up in your loft space or outside somewhere,
>> rather than faff around with rather iffy indoor things?...
>> -- 
>> Tony Sayer
>>
>>
> I do have this for my Hi-Fi listening on a completely different set up. 
> The one I am talking about sits in the kitchen,
>

"Brian Gaff"  wrote in message
news:6Eurk.46361$E41.7677@text.news.virginmedia.com...
> Well, cannot say I'm surprised really. Welcome to the joys of indoor
> reception
> I imagine  just dangling a screwdriver out the back  might also give
> better results.
> It sounds to me  as if you have plenty of signal, but its of course
> bouncing around in the  building and this is why you get all sorts of
> strange effects.
<snip top post>
>
>
That's what it sounds like to me, what he needs is an aerial up in the 
clear,
with little or no gain.

A discone like the one at Maplins
http://www.maplin.co.uk/Module.aspx?ModuleNo=29609&criteria=discone&doy=22m8

Up high on a pole above the roof would be ideal,
and could also be used for DAB on 200MHz.

If the feed isn't too long, simply use RG58 or any cheap coax

Steve Terry

"Steve Terry"  wrote in message 
news:g8nd50$vvk$1@news.albasani.net...
> "Brian Gaff"  wrote in message
> news:6Eurk.46361$E41.7677@text.news.virginmedia.com...
>> Well, cannot say I'm surprised really. Welcome to the joys of indoor
>> reception
>> I imagine  just dangling a screwdriver out the back  might also give
>> better results.
>> It sounds to me  as if you have plenty of signal, but its of course
>> bouncing around in the  building and this is why you get all sorts of
>> strange effects.
> <snip top post>
>>
>>
> That's what it sounds like to me, what he needs is an aerial up in the 
> clear,
> with little or no gain.
>
> A discone like the one at Maplins
> http://www.maplin.co.uk/Module.aspx?ModuleNo=29609&criteria=discone&doy=22m8

A non-directional discone wouldn't help if the problem is multipath.

Bill

"Bill Wright"  wrote in message 
news:Zr6dnYaNKNgjxDLVnZ2dnUVZ8rOdnZ2d@pipex.net...
>
> "Steve Terry"  wrote in message 
> news:g8nd50$vvk$1@news.albasani.net...
>> "Brian Gaff"  wrote in message
>> news:6Eurk.46361$E41.7677@text.news.virginmedia.com...
>>> Well, cannot say I'm surprised really. Welcome to the joys of indoor
>>> reception
>>> I imagine  just dangling a screwdriver out the back  might also give
>>> better results.
>>> It sounds to me  as if you have plenty of signal, but its of course
>>> bouncing around in the  building and this is why you get all sorts 
>>> of
>>> strange effects.
>> <snip top post>
>>>
>>>
>> That's what it sounds like to me, what he needs is an aerial up in 
>> the clear,
>> with little or no gain.
>>
>> A discone like the one at Maplins
>> http://www.maplin.co.uk/Module.aspx?ModuleNo=29609&criteria=discone&doy=22m8
>
> A non-directional discone wouldn't help if the problem is multipath.
>
> Bill
>


I'm not one to ever knock the Great William, but in this case (as I read 
the thread) you may not be quite right (sic!)

If there are signal effects inside the house caused by people moving 
around then it may be multipath having effect but inside only. This can 
happen at both weak and strong signal levels but IME often not 'in the 
middle.' Thence almost any external aerial will relieve the problem. 
However in most instances a horizontal will be more effective than a 
vertical albeit it won't work too well with DAB.


-- 
Woody

harrogate three at ntlworld dot com

Woody wrote:

> I'm not one to ever knock the Great William, but in this case (as I read 
> the thread) you may not be quite right (sic!)
> 
> If there are signal effects inside the house caused by people moving 
> around then it may be multipath having effect but inside only. This can 
> happen at both weak and strong signal levels but IME often not 'in the 
> middle.' Thence almost any external aerial will relieve the problem. 
> However in most instances a horizontal will be more effective than a 
> vertical albeit it won't work too well with DAB.

The OP's area of Oxford has large car factory buildings, coupled with the 
network radio transmitter chucking 46kW of ERP out at a distance of just 5 miles.
A recipe to produce multipath. Perhaps there's not much, but there could be 
enough to produce audible warbling noise on R3 in stereo. (The OP's desired 
radio station)


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

"Woody"  wrote in message 
news:7uOrk.89150$Mn3.87768@newsfe30.ams2...
> I'm not one to ever knock the Great William, but in this case (as I read 
> the thread) you may not be quite right (sic!)
>
> If there are signal effects inside the house caused by people moving 
> around then it may be multipath having effect but inside only. This can 
> happen at both weak and strong signal levels but IME often not 'in the 
> middle.' Thence almost any external aerial will relieve the problem. 
> However in most instances a horizontal will be more effective than a 
> vertical albeit it won't work too well with DAB.

Far be it from me to dispute even for one second the towering wisdom of the 
Great Woody, but dare I in all humility mention that he has got the wrong 
end of the stick? My comment referred to the suggestion earlier in the 
thread that there were large buildings in the area causing multipath. In any 
case, a discone is an absurd suggestion when the problem is simply poor FM 
radio reception. It will encourage reception of all sorts of strong 
out-of-band signals which could cause weird effects, it is not directional, 
it looks like M15 have moved in, it has lousy gain, and it costs more than a 
two element FM aerial.

When reception is affected by the signal bouncing around inside a building 
this is not usually regarded as 'multipath'. With such a short delay the 
effect is purely the constructive or subtractive combination of signals, 
causing areas of high, low, or even zero field strength. These standing wave 
effects are completely different to the effects of true multipath where the 
delay difference between paths is significant.

I hope that the Great Woody will forgive this insolent interjection.

I remain the Great Woody's craven pupil,

Bill

The message <7uOrk.89150$Mn3.87768@newsfe30.ams2>
from "Woody"  contains these words:

> "Bill Wright"  wrote in message 
> news:Zr6dnYaNKNgjxDLVnZ2dnUVZ8rOdnZ2d@pipex.net...
> >
> > "Steve Terry"  wrote in message 
> > news:g8nd50$vvk$1@news.albasani.net...
> >> "Brian Gaff"  wrote in message
> >> news:6Eurk.46361$E41.7677@text.news.virginmedia.com...
> >>> Well, cannot say I'm surprised really. Welcome to the joys of indoor
> >>> reception
> >>> I imagine  just dangling a screwdriver out the back  might also give
> >>> better results.
> >>> It sounds to me  as if you have plenty of signal, but its of course
> >>> bouncing around in the  building and this is why you get all sorts 
> >>> of
> >>> strange effects.
> >> <snip top post>
> >>>
> >>>
> >> That's what it sounds like to me, what he needs is an aerial up in 
> >> the clear,
> >> with little or no gain.
> >>
> >> A discone like the one at Maplins
> >> http://www.maplin.co.uk/Module.aspx?ModuleNo=29609&criteria=discone&doy=22m8
> >
> > A non-directional discone wouldn't help if the problem is multipath.
> >
> > Bill
> >


> I'm not one to ever knock the Great William, but in this case (as I read 
> the thread) you may not be quite right (sic!)

> If there are signal effects inside the house caused by people moving 
> around then it may be multipath having effect but inside only. This can 
> happen at both weak and strong signal levels but IME often not 'in the 
> middle.' Thence almost any external aerial will relieve the problem. 
> However in most instances a horizontal will be more effective than a 
> vertical albeit it won't work too well with DAB.

 Whilst an external antenna will overcome the cancellation effects
inherent with an indoor antenna at vhf, if it's not reasonably
directional, the effects of multipath can produce a very harsh
distortion in a vhf fm reciever, especially so in the case of stereo
reception.

 How badly this effect manifests itself will also depend on the
capability of the FM reciever to lock onto the strongest of the signals
being recieved, whether it be the direct signal or a reflected one
(either _ONE_ will do). The parameter in question being "Capture Ratio",
expressed as a db difference between the strongest and the next
strongest out of the mix of direct and reflected signals.

 A cheap and cheerful reciever would probably have a capture ratio in
the region of 6db, whilst a high quality reciever would boast a figure
in the region of 3 to 1 db (the lower the better). Using a directional
antenna to line up on the strongest signal source (which could be a
reflection rather than the direct signal, if needs be) can eliminate the
multipath distortion problem completely.

 In this regard, you won't necessairly be aiming to get the strongest
signal from your chosen source (direct or a stronger reflection). It'll
be a case of trying to drop the strongest unwanted signal into, or close
to, a null to make the chosen source stand up above the competing
reflections (or direct signal, if you've chosen a reflection source
that's stronger).

 If you want to enjoy fm stereo broadcasts without multipath distortion,
you'll need an outdoor directional antenna and a reciever with a decent
capture ratio figure (3db or lower). In most cases a 3 or 4 element
folded dipole yagi will suffice. OTOH, if all you need is mono
reception, you can probably site your portable fm radio (or simple
folded dipole made up from 300 ohm ribbon cable) to reduce multipath
distortion to acceptable levels for 'Easy Listening'.

 HTH

-- 
Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

In article , Johnny B Good
 wrote:

[snip]

>  How badly this effect manifests itself will also depend on the
> capability of the FM reciever to lock onto the strongest of the signals
> being recieved, whether it be the direct signal or a reflected one
> (either _ONE_ will do). The parameter in question being "Capture Ratio",
> expressed as a db difference between the strongest and the next
> strongest out of the mix of direct and reflected signals.

Capture Ratio is intended to show the ability to reject a different signal
in the same channel as the desired signal. i.e. where there is no coherent
relationship between the carriers or modulation. This is a different
situation to where additional signals are multipath delayed versions of the
main signal.

So although a low value for the Capture Ratio would be disirable, that
won't ensure that multipath is rejected.

The problem is that multipath can alter the recieved phase modulation as
well as the amplitude of the signal. Good Capture Ratio helps prevent the
cross mod into AM having an effect, but can't remove the changes to the
phase modulation. So as explained your best bet to deal with multipath is a
directional antenna, and perhaps aligning this to minimise the multipath
contribution.

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

The message 
from Jim Lesurf  contains these words:

> In article , Johnny B Good
>  wrote:

> [snip]

> >  How badly this effect manifests itself will also depend on the
> > capability of the FM reciever to lock onto the strongest of the signals
> > being recieved, whether it be the direct signal or a reflected one
> > (either _ONE_ will do). The parameter in question being "Capture Ratio",
> > expressed as a db difference between the strongest and the next
> > strongest out of the mix of direct and reflected signals.

> Capture Ratio is intended to show the ability to reject a different signal
> in the same channel as the desired signal. i.e. where there is no coherent
> relationship between the carriers or modulation. This is a different
> situation to where additional signals are multipath delayed versions of the
> main signal.

> So although a low value for the Capture Ratio would be disirable, that
> won't ensure that multipath is rejected.

 Although the two cases, other TX on same channel versus multipath, are
subtley different, a low capture ratio figure will, nevertheless,
significantly enhance the effect of using a directional antenna to pick
out the best signal.

> The problem is that multipath can alter the recieved phase modulation as
> well as the amplitude of the signal. Good Capture Ratio helps prevent the
> cross mod into AM having an effect, but can't remove the changes to the
> phase modulation. So as explained your best bet to deal with multipath is a
> directional antenna, and perhaps aligning this to minimise the multipath
> contribution.

 No argument over the need for a directional antenna when multipath is
an issue, but a low capture ratio figure of merit can drop the need for
a 6 element down to a 3 or even a 2 element antenna so shouldn't be
totally discounted as a benefit in this situation (however, you might
need the 6 element over a two element antenna anyway simply to improve
the S/N ratio :-).

-- 
Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

In article , Johnny B Good
 wrote:
> The message  from Jim Lesurf
>  contains these words:


> > Capture Ratio is intended to show the ability to reject a different
> > signal in the same channel as the desired signal. i.e. where there is
> > no coherent relationship between the carriers or modulation. This is a
> > different situation to where additional signals are multipath delayed
> > versions of the main signal.

> > So although a low value for the Capture Ratio would be disirable, that
> > won't ensure that multipath is rejected.

>  Although the two cases, other TX on same channel versus multipath, are
> subtley different, a low capture ratio figure will, nevertheless,
> significantly enhance the effect of using a directional antenna to pick
> out the best signal.

Depends on how you are using the word "enhance". :-)

The Capture effect essentially works by reducing sensitivity to amplitude
fluctuations which alter the output of the demodulation. Aligning the
antenna to improve the direct/miltipath ratio works by reducing the level
of multipath. Thus the two mechanisms are quite distinct.

So if you mean "using both mechanisms can give a better result than just
using one" by "enhance" then I'd agree. But this isn't because the two are
inherently related.

Also Capture in reality varies with overall signal level. So a lower input
level tends to degrade the Capture Ratio value. 

> > The problem is that multipath can alter the recieved phase modulation
> > as well as the amplitude of the signal. Good Capture Ratio helps
> > prevent the cross mod into AM having an effect, but can't remove the
> > changes to the phase modulation. So as explained your best bet to deal
> > with multipath is a directional antenna, and perhaps aligning this to
> > minimise the multipath contribution.

>  No argument over the need for a directional antenna when multipath is
> an issue, but a low capture ratio figure of merit can drop the need for
> a 6 element down to a 3 or even a 2 element antenna so shouldn't be
> totally discounted as a benefit in this situation (however, you might
> need the 6 element over a two element antenna anyway simply to improve
> the S/N ratio :-).

Particularly if you are pointing the main beam axis away from the main
direction of arrival to put a response dip in the multipath direction.  :-)

I'd be interested in data/analysis to support the above figures. Can you
point me at the work it is based upon?

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

The message 
from Jim Lesurf  contains these words:

> In article , Johnny B Good
>  wrote:

====snip====

> >  No argument over the need for a directional antenna when multipath is
> > an issue, but a low capture ratio figure of merit can drop the need for
> > a 6 element down to a 3 or even a 2 element antenna so shouldn't be
> > totally discounted as a benefit in this situation (however, you might
> > need the 6 element over a two element antenna anyway simply to improve
> > the S/N ratio :-).

> Particularly if you are pointing the main beam axis away from the main
> direction of arrival to put a response dip in the multipath direction.  :-)

> I'd be interested in data/analysis to support the above figures. Can you
> point me at the work it is based upon?

 Well, after some 30 odd years, the best I can suggest is that you check
out the back issues of "Wireless World" circa the mid to late 70s.

-- 
Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

In article , Johnny B Good
 wrote:
> The message  from Jim Lesurf
>  contains these words:

> > In article , Johnny B
> > Good  wrote:

> ====snip====

> > >  No argument over the need for a directional antenna when multipath
> > > is an issue, but a low capture ratio figure of merit can drop the
> > > need for a 6 element down to a 3 or even a 2 element antenna so
> > > shouldn't be totally discounted as a benefit in this situation
> > > (however, you might need the 6 element over a two element antenna
> > > anyway simply to improve the S/N ratio :-).

> > Particularly if you are pointing the main beam axis away from the main
> > direction of arrival to put a response dip in the multipath direction.
> >  :-)

> > I'd be interested in data/analysis to support the above figures. Can
> > you point me at the work it is based upon?

>  Well, after some 30 odd years, the best I can suggest is that you check
> out the back issues of "Wireless World" circa the mid to late 70s.

I could as we have the 1970s issues of WW in our Uni Library. But it
would help if you could be somewhat more specific than "circa mid to late
70s". That is rather vague. Doesn't seem worth my while to spend hours
trawling for some kind of references when it would be simpler to
decide you are unable to actually offer any data/analysis. If you have
some, you presumable know its source.

The problem here is that you have made a rather sweeping assertion about
the relative ability of two quite distinct methods for altering the
effect of multipath. Yet the two mechanisms differ and can be expected
to have an impace that varies with circumstances. When asked for evidence
your above response is, alas, little more that an assertion that evidence
exists... but without much detail or allowance for circumstances. So not
much help, I'm afraid.

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

The message 
from Jim Lesurf  contains these words:

> In article , Johnny B Good
>  wrote:
> > The message  from Jim Lesurf
> >  contains these words:

> > > In article , Johnny B
> > > Good  wrote:

> > ====snip====

> > > >  No argument over the need for a directional antenna when multipath
> > > > is an issue, but a low capture ratio figure of merit can drop the
> > > > need for a 6 element down to a 3 or even a 2 element antenna so
> > > > shouldn't be totally discounted as a benefit in this situation
> > > > (however, you might need the 6 element over a two element antenna
> > > > anyway simply to improve the S/N ratio :-).

> > > Particularly if you are pointing the main beam axis away from the main
> > > direction of arrival to put a response dip in the multipath direction.
> > >  :-)

> > > I'd be interested in data/analysis to support the above figures. Can
> > > you point me at the work it is based upon?

> >  Well, after some 30 odd years, the best I can suggest is that you check
> > out the back issues of "Wireless World" circa the mid to late 70s.

> I could as we have the 1970s issues of WW in our Uni Library. But it
> would help if you could be somewhat more specific than "circa mid to late
> 70s". That is rather vague. Doesn't seem worth my while to spend hours
> trawling for some kind of references when it would be simpler to
> decide you are unable to actually offer any data/analysis. If you have
> some, you presumable know its source.

> The problem here is that you have made a rather sweeping assertion about
> the relative ability of two quite distinct methods for altering the
> effect of multipath. Yet the two mechanisms differ and can be expected
> to have an impace that varies with circumstances. When asked for evidence
> your above response is, alas, little more that an assertion that evidence
> exists... but without much detail or allowance for circumstances. So not
> much help, I'm afraid.

 I'm awfully sorry about that, but my answer did rather imply I was
unable to remember such source references with any precision, it was
over thirty years ago, after all!

 At the time, the benefit of low capture ratio was stated to apply not
only to co-channel interference from other transmitter sources but also
to multipath from that most co-channel of all interfereing sources, an
unwanted reflection of the same transmitter. Now you're claiming this is
not in actual fact the case.

 I've no doubt you have access to more recent research findings on the
subject which demonstrate your assertion. Perhaps, in this circumstance,
it would be simpler for you to provide the references to _your_ sources
(preferably links) so I may update my 30 year old knowledge of this
matter.

-- 
Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

"Johnny B Good"  wrote in message 
news:313030303737303648BA175C80@plugzetnet.co.uk...
> At the time, the benefit of low capture ratio was stated to apply not
> only to co-channel interference from other transmitter sources but also
> to multipath from that most co-channel of all interfereing sources, an
> unwanted reflection of the same transmitter. Now you're claiming this is
> not in actual fact the case.

I have to say that in all the stuff I've read over the years I've never seen 
any suggestion that the capture effect could assist in reducing mulripath 
effects. When I read your post on the subject my eyebrows went up, but I 
couldn't think of any specific source that refuted your claim.

I would have thought that if capture effect did assist in defeating 
multipath effects there would be much made of it.

Bill

In article , Johnny B Good
 wrote:
> The message  from Jim Lesurf
>  contains these words:

>

>  I've no doubt you have access to more recent research findings on the
> subject which demonstrate your assertion. Perhaps, in this circumstance,
> it would be simpler for you to provide the references to _your_ sources
> (preferably links) so I may update my 30 year old knowledge of this
> matter.

The problem here is that you - not I - were making a specific and sweeping
assertion about the use of antenna alignment and a given capture ratio as
being equivalent in effect - with no real detail as to what circumstances,
etc, for which that might be correct or incorrect. I have simply been
pointing out that the two mechanisms are quite different, so can be
expected to only give the same level of effect for specific circumstances.

I was therefore asking for any evidence you have to back your assertion. 

Your response makes plain you have no evidence, just a general
recollection. From this it looks like you have forgotten about any
qualifying circumstances, etc, that might have been present in what you
read, and have now forgotten/lost.

It is normal academic/scientific/engineering practice for the person making
an assertion to be able to provide evidence, etc. So as things stand I am
happy to conclude that your claim probably only applies in some cases, with
details, etc, unknown.

FWIW I did do some analysis on multipath effects on UK Band II type FM
Stereo a while ago for an article, and the results were what made me query
your statements. But the analysis has been shelved as I've been doing work
on other topics. However when I resume it and the article is published I'll
try to mention it here in case anyone is interested.

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

The message 
from Jim Lesurf  contains these words:

> In article , Johnny B Good
>  wrote:
> > The message  from Jim Lesurf
> >  contains these words:

> >

> >  I've no doubt you have access to more recent research findings on the
> > subject which demonstrate your assertion. Perhaps, in this circumstance,
> > it would be simpler for you to provide the references to _your_ sources
> > (preferably links) so I may update my 30 year old knowledge of this
> > matter.

> The problem here is that you - not I - were making a specific and sweeping
> assertion about the use of antenna alignment and a given capture ratio as
> being equivalent in effect - with no real detail as to what circumstances,
> etc, for which that might be correct or incorrect. I have simply been
> pointing out that the two mechanisms are quite different, so can be
> expected to only give the same level of effect for specific circumstances.

> I was therefore asking for any evidence you have to back your assertion. 

> Your response makes plain you have no evidence, just a general
> recollection. From this it looks like you have forgotten about any
> qualifying circumstances, etc, that might have been present in what you
> read, and have now forgotten/lost.

> It is normal academic/scientific/engineering practice for the person making
> an assertion to be able to provide evidence, etc. So as things stand I am
> happy to conclude that your claim probably only applies in some cases, with
> details, etc, unknown.

> FWIW I did do some analysis on multipath effects on UK Band II type FM
> Stereo a while ago for an article, and the results were what made me query
> your statements. But the analysis has been shelved as I've been doing work
> on other topics. However when I resume it and the article is published I'll
> try to mention it here in case anyone is interested.

 Well, I'll admit I'm no academic. I was going by 'recieved wisdom'
(maybe recieved wis-dumb was nearer the truth?), which strongly implied,
if it didn't state outright, that reduction of multipath distortion was
one of the benefits to having a low capture ratio db figure. It all
seemed a reasonable hypothesis at the time. Maybe I'd simply given up on
the Hi-Fi mags too soon before this myth was blown.

 I'll appreciate the enlightenment, if no one else does. Googling didn't
produce any definitive results to say one way or the other.

-- 
Regards, John.

 Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

In article , Bill Wright
 wrote:

> "Johnny B Good"  wrote in message
> news:313030303737303648BA175C80@plugzetnet.co.uk...
> > At the time, the benefit of low capture ratio was stated to apply not
> > only to co-channel interference from other transmitter sources but
> > also to multipath from that most co-channel of all interfereing
> > sources, an unwanted reflection of the same transmitter. Now you're
> > claiming this is not in actual fact the case.

> I have to say that in all the stuff I've read over the years I've never
> seen any suggestion that the capture effect could assist in reducing
> mulripath effects. When I read your post on the subject my eyebrows
> went up, but I couldn't think of any specific source that refuted your
> claim.

> I would have thought that if capture effect did assist in defeating
> multipath effects there would be much made of it.

My understanding is that the problem here is that the effect of Capture
Ratio upon multipath depends on a set of other variables/circumstances.
This makes it hard for someone to give a specific figure for how useful it
might be as a generalisation, or compare a CR value with something quite
different like antenna alignment/pattern.  Hence my challenging JBGs
comments.

Given the above, hardly surprising if workers/authors treat the two things
seperately.

Like yourself, I can't recall anyone making similar claims backed by a
decent analysis or results. But it is now on my (long) 'to do' list to see
if I can stumble over anything in WW that might be the source of what he
has written. Don't hold yer breath, though...  :-)

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

In article , Johnny B
Good
 wrote:

[big snip]

>  Well, I'll admit I'm no academic. I was going by 'recieved wisdom'
> (maybe recieved wis-dumb was nearer the truth?), which strongly implied,
> if it didn't state outright, that reduction of multipath distortion was
> one of the benefits to having a low capture ratio db figure. It all
> seemed a reasonable hypothesis at the time.

It is. You can expect that as a general tendency. But that does not mean
you can simply equate a given antenna alignment with a given CR value.
Other circumstances/variable matter.


> Maybe I'd simply given up on
> the Hi-Fi mags too soon before this myth was blown.

>  I'll appreciate the enlightenment, if no one else does. Googling didn't
> produce any definitive results to say one way or the other.

Problem here, I think, is that detailed analysis of such 'imperfections'
with FM and drawing useful conclusions is quite difficult to do! You may
have noticed that most university or college level textbooks stick to just
telling students about basic sinusoidal modulation for FM. Often going
further and only doing 'narrow band' and 'wideband' approximate cases.

Reason being that more practical cases with complicated input signals are
harder to evaluate - and often produce results that are only relevant for
that specific case! From the viewpoint of teachers and students this is
awkward as there are no simple rules, so it all becomes hard to evaluate or
use. Ditto for authors of books or articles as you risk analysing
situations that aren't of interest to most readers.  :-)

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

Jim Lesurf  wrote:

> Like yourself, I can't recall anyone making similar claims backed by a
> decent analysis or results. But it is now on my (long) 'to do' list to see
> if I can stumble over anything in WW that might be the source of what he
> has written. Don't hold yer breath, though...  :-)

I have a few printed indexes from the 1970s and '80s and have turned up
two articles on multipath distortion by Pat Hawker. They do not address
the precise issue you are discussing, but they maight have some useful
references: April 1980, p45; April 1981, p83.

-- 
Alan Pemberton
Sheffield, South Yorkshire, England
To e-mail me directly, please visit
<http://www.pembers.freeserve.co.uk/index.html#Mail-me>

In article
<1immzlc.umwovqgafaiwN%Spambox@pembers.freeserve.co.uk.invalid>, Alan
Pemberton <Spambox@pembers.freeserve.co.uk.invalid> wrote:
> Jim Lesurf  wrote:

> > Like yourself, I can't recall anyone making similar claims backed by a
> > decent analysis or results. But it is now on my (long) 'to do' list to
> > see if I can stumble over anything in WW that might be the source of
> > what he has written. Don't hold yer breath, though...  :-)

> I have a few printed indexes from the 1970s and '80s and have turned up
> two articles on multipath distortion by Pat Hawker. They do not address
> the precise issue you are discussing, but they maight have some useful
> references: April 1980, p45; April 1981, p83.

Thanks.  :-)   I'll make a note of the above and look at the issues when I
get a chance.

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

On 03 Sep, noise@audiomisc.co.uk wrote:
> In article
> <1immzlc.umwovqgafaiwN%Spambox@pembers.freeserve.co.uk.invalid>, Alan
> Pemberton <Spambox@pembers.freeserve.co.uk.invalid> wrote:
> > Jim Lesurf  wrote:

> > I have a few printed indexes from the 1970s and '80s and have turned
> > up two articles on multipath distortion by Pat Hawker. They do not
> > address the precise issue you are discussing, but they maight have
> > some useful references: April 1980, p45; April 1981, p83.

> Thanks.  :-)   I'll make a note of the above and look at the issues when
> I get a chance.

I've now read the relevant issues, and made copies of the above, plus some
letters in WW prompted by them.

Thanks again for pointing them out. As you say, they don't cover the
specific claims JBG made. But they are very useful as reference info for
the work for an article I plan on the effects of multipath on FM stereo.

I also like the comments Hawker made in the first column of the first
article. The quote from Russell is a good one for the 'audio' field, and
his view that multipath effects on VHF FM stereo have been rather
overlooked and forgotten is one I agree with. With luck, I can rectify that
omission to some extent. :-)

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html