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 lightning
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 probably
somewhere in Africa, The reception area is not really a "point" but more
like a area about 100km across.
The path-loss would be an interesting calculation :-))
Alan G3NYK
----- Original Message -----
From: "Roger Lapthorn" <[email protected]>
To: <[email protected]>
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 lines
going from a point in the northern hemisphere to the southern hemisphere
at the conjugate point i.e. as far south as north of the magnetic equator.
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 can
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 became
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 this 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 Schäfer <[email protected]>
> 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) back in
the
>> 1965 book "Whistlers and Related Ionospheric Phenomena" by J.A.Hellliwell
(I
>> have a copy). This could mean signals getting to, for example, conjugate
>> locations in the southern hemisphere (S.Africa?) with relatively low
>> 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
>
>
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