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Date: Wed, 06 Oct 2010 00:09:52 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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Subject: Re: VLF: Re: DK7FC's 7th VLF kite experiment
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Piotr,

I just saw that i misunderstood something: I do not need to include the=20
reduced antenna efficiency since it is already included, since the=20
calculation is for 1 A Antenna current, right? So the reduced radiation=20
resistance is already included in the calculation. All that has to be=20
kept in mind is the reduced coil losses at higher frequencies and the=20
lower earth losses but this effect is not so much the point i think (< 3=
=20
dB). So, it must be an advantage to transmit on 6470 Hz! We will check=20
this!! :-)

Will YOU try to receive the signal as well? Would be a pleasure for me=20
to send something to you :-)

73, Stefan



Am 05.10.2010 22:53, schrieb Piotr Mlynarski:
> Stefan Sch=E4fer pisze:
>>
>> The link to the IEEE paper is very interesting as well! Maybe the=20
>> scientists over there are interested to take part on the experiments?=
=20
>> Do you know some of them? Maybe we can combine the amateurs and the=20
>> scientific work, although they will have no appreciation if i=20
>> transmit "73" instead of a constant carrier ;-)
>>
>> PS: If you have the time, could you give us some ideas to compare=20
>> 8970 Hz and 6470 Hz? Or even 5170 Hz if i can set up a 300m vertical?=
=20
>> Maybe i should do the first test on 5170 Hz before you take the=20
>> effort ;-)
>>
>> Stefan/DK7FC
>>
>>
>>
>
> Hello Stefan, VLF,
>
> you will find (attached)  graph showing  strength of E-field as a=20
> function of distance calculated for that three  frequencies i.e.=20
> 8970,6470,5170 Hz.
> At this range of frequencies going down with its values indeed gives=20
> an increase in the field strength but what is not displayed here is a=20
> rapid attenuation
> of the field strength if one goes further down with frequency thus=20
> approaching so called cutoff frequency which is defined as
> fc =3D velocity of light/(2 * ionosphere height); say, h =3D 80 km so fc=
 =3D=20
> 1.88 kHz ; h =3D 70 km so fc =3D 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 =3D 1A, length =3D200meters. i took only one height =3D 80 km
>
> according to the IEEE paper.. no, i do not know its authors - it was=20
> just found ( and saved :)  ) during my literature search.
>
>                                                                       =
                                   =20
> 73, Piotr, sq7mpj
>
> qth: Lodz  /jo91rs/
>