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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <AANLkTin_33F-mJQyrhbBqdSyY0HNFEizst=3iSWywUM_@mail.gmail.com>
Date: Wed, 16 Mar 2011 00:23:11 -0000
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Subject: LF: Re: VLF reception - easily mistaken!
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Hi Roger yes this is an old one. The thing is that most of the weak very
steady frequency lines one sees one cannot afford to ID by just the
frequency but it is one bit of data. I have found in the past that a small
freqency jump at a period that relates to the resolution being used it much
more sure. It doesnt need a full call-sign or even a morse letter (this is
not a qso band.....yet) a square wave shift is best. It is then possible to
do an auto-correlation on the signal to dig it out and prove the case.  One
can imagine a 30 min period shift of 50mHz :-)) I have found in the past
that the odd spurious transmissions never (well I never saw one) jump
frequency regularly. I tried to get our AMRAD friends to incorporate that on
their Part 5 station back around 2000 but it wasnt feasible with the TX.and
they were not really interested in DX, so the transmission was lost amonst
the Loran lines.

Alan G3NYK


----- Original Message ----- 
From: "Roger Lapthorn" <rogerlapthorn@gmail.com>
To: <rsgb_lf_group@blacksheep.org>; "Eddie" <g3zjo@talktalk.net>;
<oe5odl@langwelle.at>
Sent: Tuesday, March 15, 2011 10:13 PM
Subject: LF: VLF reception - easily mistaken!


> A word of caution to those of us looking for *very* weak signals around
> 8-9kHz.....
>
> DJ8WX was copied here overnight without any doubt and my grabber was
clearly
> able to see his close-down around 0700 today. The frequency and the trace
> timing corresponded perfectly. Likewise with G3XIZ and DK7FC/P some weeks
> ago.
>
> This evening I was looking very carefully again at the Spectrum Lab screen
> from the last 24 hours in 424uHz BW and readjusting audio gain ranges,
> screen colour saturation and contrast. Out of the noise appeared another
> very very faint line, not at 8.970022 but at 8.96998kHz. I've attached the
> screen shot here (I have overlaid it with the time for clarity).
>
> My immediate reaction was this must be Ossi OE5ODL. Then I checked his
> grabber and saw he was not operational overnight last night! So, what
looked
> like a trace on his frequency *cannot* be him. It must instead be some
> artefact of SL or something else.
>
> So, *Mal is right* (did I just say that? :-) ) that we have to be
> *very *careful
> when seeing traces at specific frequencies: it may be an indication of a
> given station, but without some modulation or turning on/off of the
carrier
> a doubt remains.
>
> Sadly I don't think I did see Ossi today after all, but I shall keep
> looking.
>
> 73s
> Roger G3XBM
> -- 
> g3xbm-qrp.blogspot.com/
> www.g3xbm.co.uk
> www.youtube.com/user/g3xbm
> <http://vlf_grabber>G3XBM   GQRP 1678    ISWL G11088
>