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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