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Re: VLF: Re: DK7FC's 7th VLF kite experiment

To: [email protected]
Subject: Re: VLF: Re: DK7FC's 7th VLF kite experiment
From: Stefan Schäfer <[email protected]>
Date: Wed, 06 Oct 2010 00:09:52 +0200
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Piotr,

I just saw that i misunderstood something: I do not need to include the reduced antenna efficiency since it is already included, since the calculation is for 1 A Antenna current, right? So the reduced radiation resistance is already included in the calculation. All that has to be kept in mind is the reduced coil losses at higher frequencies and the lower earth losses but this effect is not so much the point i think (< 3 dB). So, it must be an advantage to transmit on 6470 Hz! We will check this!! :-)

Will YOU try to receive the signal as well? Would be a pleasure for me to send something to you :-)

73, Stefan



Am 05.10.2010 22:53, schrieb Piotr Mlynarski:
Stefan Schäfer pisze:

The link to the IEEE paper is very interesting as well! Maybe the scientists over there are interested to take part on the experiments? Do you know some of them? Maybe we can combine the amateurs and the scientific work, although they will have no appreciation if i transmit "73" instead of a constant carrier ;-)

PS: If you have the time, could you give us some ideas to compare 8970 Hz and 6470 Hz? Or even 5170 Hz if i can set up a 300m vertical? Maybe i should do the first test on 5170 Hz before you take the effort ;-)

Stefan/DK7FC




Hello Stefan, VLF,

you will find (attached) graph showing strength of E-field as a function of distance calculated for that three frequencies i.e. 8970,6470,5170 Hz. At this range of frequencies going down with its values indeed gives an increase in the field strength but what is not displayed here is a rapid attenuation of the field strength if one goes further down with frequency thus approaching so called cutoff frequency which is defined as fc = velocity of light/(2 * ionosphere height); say, h = 80 km so fc = 1.88 kHz ; h = 70 km so fc = 2.14 kHz etc...
(within the  used  propagation model of an earth-ionosphere waveguide )

The present numerical values were calculated using  your 7th setup i.e.
ant I = 1A, length =200meters. i took only one height = 80 km

according to the IEEE paper.. no, i do not know its authors - it was just found ( and saved :) ) during my literature search.

73, Piotr, sq7mpj

qth: Lodz  /jo91rs/


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