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Message-ID: <001601c7bcd9$710dbf80$0300a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <003801c7bccd$31a5de60$876a6a58@wgt01>
Date: Mon, 2 Jul 2007 19:47:24 +0100
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Subject: LF: Re: 500 - Signal on 504 KHz
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Hi Gary. I dont think that unless you have a big loop or you have a very
local BC station that you will see any improvement for shielding the loop.
In fact it might even be worse, due to the reduction in Q that comes with
the extra stray capacitance. The side of the loop is small with respect to a
wavelength so the amount of "electric" field pick-up will be so small as to
make the contribution negligable. It is different with an HF loop.

On the point about RTE yes it is just across the water from you. It might be
worth seeing if there is any improvement by trapping (or notching) the
fundamental. I would not imagine there is with a tuned loop. If they go DRM
I guess that we will get a general increase in noise level across the band.
It might be worth making some measurements because although we only have
experimental permits BC stations are supposed to radiate clean
transmissions. It would not be good for DRM to be perceived to radiate muck
on harmonics.

On the point of "QRM" I am receiving a very weak signal on 502.5. I know
that is where Adrian G4GDR transmits but this is on almost continuously. I
thought I had identified it as Adrian when Jim worked him the other day as
it seemed to go off when Jim was transmitting. I am now wondering if that
was just due to the big signal I get from Jim. I need averaging to see it
but if looks like it could be morse and it "pings up" occasionally. I dont
know whether Adrian does call a lot ...because he has a valve rig I guess he
doesnt beacon and is probably not that stable (??).

 Cheers de Alan G3NYK

----- Original Message -----
From: Gary - G4WGT <g4wgt@tiscali.co.uk>
To: LF (Rsgb LF Group) <rsgb_lf_group@blacksheep.org>
Sent: 02 July 2007 18:19
Subject: LF: 500 - Signal on 504 KHz


> Hi All,
>
> During my monitoring of 500 KHz I have almost always seen a line on
SpecLab
> at 504.0 KHz. Whilst attempting to improve a shielded loop for 500 KHz I
> have been receiving the signal on 504.0 KHz stronger & stronger with
> accompanying hetrodyne. After todays changes to my loop the signal has
> become so strong that I now hear garbled audio & SpecLab is showing audio
> sidebands (see capture attached). I notice that there is a line at the
same
> frequency on the Bimingham Grabber some of the time. I first thought it
was
> some product of mixing strong signals in the MF range. I decided to try to
> work it out & realised that in fact it is the second harmonic of RTE Radio
1
> on 252 KHz. I have studied the uninteligable audio pattern & it does
relate
> to  that signal.
>
> I must admit that I don't know if it due to improvements or some other
quirk
> of my loop or just the fact that the filtering at RTE Radio 1 is poor.
> Although this signal has got stronger with changes to my loop there
doesn't
> appear to be the same improvement with normal 500 KHz signals.
>
> Perhaps someone can shed some light on this for me.
>
> 73
>
> Gary - G4WGT - IO83qp
>
>