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Date: Tue, 05 Oct 2010 23:54:46 +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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Hello Piotr,

Again thanks for your work. The comparison of the 3 bands is very=20
interesting. If i include the reduced antenna efficiency it is anyway an=
=20
advantage to transmit on lower frequencies, at least below 2000 km. So,=20
if the QRN situation @ the RX side on these 3 bands is about equal and=20
if we think about the lower QRN on 46 km compared to 33 km, it could be=20
shown that 46 km is a real alternative.

What do you think when going over the alps? What might be better, 33km,=20
46km or 58 km? Your forecast please ;-) Maybe i can transmit in the 8th=20
experiment with a DFCW shift of 2,5 kHz ;-) Means, the dash appears on=20
33km and the dot on 46km. So we could compare the S/N levels with=20
negligible QRN changes within the transmissions...

I am interested in your and other's ideas!

73, Stefan/DK7FC

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/
>