On Sat, 30 Oct 2010, Stefan Schäfer wrote:
All very interesting, i cannot stop thinking about ;-)
Your plot_80km.png tells me that in 200 km distance (pretty close to
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
200km would be 1.6 wavelength :). you would really have to ask Piotr
SQ7MPJ, he has the theoretical background
but from the graphs it would seem that for relatively "short" distances
there is a frequency that gives the best field strength, and that this
frequency increases with distance. for 904km this frequency is around 4kHz
according to this model.
So, if i would use the 300m kite and switch a parallel capacitor to the
loading coil, 3x the C of the kite wire (about 5 nF/ 30 kV), i could resonate
on 2.5 kHz (crazy!). Although just 1/4 of the coils current would flow into
the wire (< 12 dB losses) my signal would be stronger in that region! Ah, i
have forgotten the lower radiation resistance of the 300m wire on this
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 antenna
since there is no need to resonate it and the earth losses are almost
independent of frequency! If the frequency decreases, the skip depth (and so
the effective loop area) increases. This might partly compensate the decrease
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
filter beforehand
VY 73
Jacek / SQ5BPF
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