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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4CC74304.3090903@iup.uni-heidelberg.de><AANLkTi=VuSjXZRSs1focCWYVZTYp+0rCj8uxUv=v5MGc@mail.gmail.com><4CC74C5E.9030203@iup.uni-heidelberg.de> <AANLkTikp5UuE7kg6o2r1Sh=Bogai+tEw7U3OSyJ8-fNv@mail.gmail.com>
Date: Tue, 26 Oct 2010 23:39:50 +0100
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Subject: Re: VLF: whistler duct AMATEUR propagation
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Hi Roger/Stefan the guys in the VLF group will point you at sites that=
 will
calculate your conjugate point. The spend time watching the www lightn=
ing
charts for activity near their point They are basically N<>S though so=
 no-go
Germany to ZL as far as I see, the problem is that the far end is prob=
ably
somewhere in Africa, The reception area is not really a "point" but mo=
re
like a area about 100km across.

The path-loss would be an interesting calculation :-))

Alan G3NYK

----- Original Message -----=20
From: "Roger Lapthorn" <rogerlapthorn@gmail.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, October 26, 2010 11:11 PM
Subject: Re: VLF: whistler duct AMATEUR propagation


Hi Stefan,

If I remember correctly, you have to visualise the magnetic field line=
s
going from a point in the  northern hemisphere  to the southern hemisp=
here
at the conjugate point i.e. as far south as north of the magnetic equa=
tor.
Signals will only be received close to this point at any strength by
propagation along the magnetic field lines in whistler duct mode.

With whistlers, triggered by a strong lightning impulse, the signal ca=
n
propagate back and forth between N/S hemispheres being more frequency
dispersed with each pass. The sound is amazing. Helliwell's book shows=
 one
strong series of audio frequency echoes lasting over a minute in the=
 sunspot
maximum of the late 1950s, but this is rare. With amateur signals we=
 would
be lucky to get from Europe to Southern Africa once before signals bec=
ame
too weak to detect.

Who would have even believed that such experiments by amateurs would=
 be
seriously considered, even 12 months ago? You and others working on th=
is are
*true* pioneers and you all deserve great credit for this. I am only
"dabbling at the edges" and have a *great* deal to learn.

73s
Roger G3XBM


2010/10/26 Stefan Sch=E4fer <schaefer@iup.uni-heidelberg.de>

> Hi Roger,
>
> Am 26.10.2010 23:18, schrieb Roger Lapthorn:
>
>> Stefan,
>>
>> The possibility of whistler duct AMATEUR propagation is fascinating=
.
There
>> are (I think) spectrograms of such propagation from NAA (~14kHz) ba=
ck in
the
>> 1965 book "Whistlers and Related Ionospheric Phenomena" by J.A.Hell=
liwell
(I
>> have a copy). This could mean signals getting to, for example, conj=
ugate
>> locations in the southern hemisphere (S.Africa?) with relatively lo=
w
>> attenuation. A chirped signal would also show whisper dispersion I=
 guess.
>>
> Yes, absolutely interesting! We will do that! And SpecLab can easily
> generate such a signal, my PA can easily transmit such a signal and=
 my
earth
> antenna can easily radiate such a (broad band) signal! :-)
>
> Any further hints/ideas, Roger (and the group)?
>
>>
>> You will need some grabbers in distant places!
>>
> Maybe ZL2AFP can help us here by receiving? :-)
>
> 73, Stefan
>
>


--=20
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088