Date: Sat, 30 Oct 2010 09:10:21 +0200 (CEST)
From: Jacek Lipkowski <sq5bpf@lipkowski.org>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <4CCB4663.2080500@iup.uni-heidelberg.de>
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Subject: Re: LF: vlf experiments-numerical considerations
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On Sat, 30 Oct 2010, Stefan Sch=E4fer wrote:

> All very interesting, i cannot stop thinking about ;-)
> Your plot_80km.png tells me that in 200 km distance (pretty close to=20
> DF6NM/DJ2LF/DK6NI/DJ6LB), 2500 Hz is the most suitable frequency.

i'm not sure how the model performs "close" to the antenna, and at 2500Hz=
=20
200km would be 1.6 wavelength :). you would really have to ask Piotr=20
SQ7MPJ, he has the theoretical background

but from the graphs it would seem that for relatively "short" distances=20
there is a frequency that gives the best field strength, and that this=20
frequency increases with distance. for 904km this frequency is around 4kHz=
=20
according to this model.

> So, if i would use the 300m kite and switch a parallel capacitor to the=
=20
> loading coil, 3x the C of the kite wire (about 5 nF/ 30 kV), i could res=
onate=20
> on 2.5 kHz (crazy!). Although just 1/4 of the coils current would flow=
 into=20
> the wire (< 12 dB losses) my signal would be stronger in that region! Ah=
, i=20
> have forgotten the lower radiation resistance of the 300m wire on this=
=20
> frequency,ok...
>
> Oh dear, should we really try a 2.5 kHz test?

yes! and a 4kHz test

> Another idea: It would be most interesting in a test on the earth antenn=
a=20
> since there is no need to resonate it and the earth losses are almost=20
> independent of frequency! If the frequency decreases, the skip depth (an=
d so=20
> the effective loop area) increases. This might partly compensate the dec=
rease=20
> of efficiency.Wow! I will prepare such a test for the next week! :-)

please tell us what the frequencies will be. i have to make a bandpass=20
filter beforehand

VY 73

Jacek / SQ5BPF

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