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Date: Sat, 31 Jul 2010 11:53:08 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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Subject: Re: VLF: DK7FC's 6th VLF kite experiment
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Hello Peter,

Better say 6,6 +-200 Hz. It is still not certain where the resonance 
will be, sorry. There are to many assumtions, estimations and calculations.

On 137 kHz the measured C for 100m is 580pF (measured with a RC bridge 
and by measuring the L and calculating C). But EZNEC shows a lower C. 
This could be, since a 100m vertical is not absolutely short against 
Lambda and so the sems to occur some impedance transformation which 
"looks/behaves" like a higherC.

On <9 kHz the 100m wire IS short against lambda and so i loose this 
benefit. There, the actual C is present. The L of my variometer part in 
the BIG coil is estimated to be 30 mH. Maybe it is even more and the 
overall L is higher than L(coil)+L(variometer) due to the better 
magnetic coupling. So maybe i have less C and more L than thought on 8,97.

When doubling the antenna height from 100m to 200m and assuming 5 pF/m 
the C is doubled as well. So i thought i will come out at 6,34 kHz 
(8,97/sqrt(2)). But this may just a rough estimate. EZNEC says the C 
factor is not 2 but 1,88 so i would come out some 100 Hz above.

So the question is:
What is the actual antenna C for 100m
What is the actual (maximum and average) L
What is the C factor when going from 100m to 200m

This are many uncertainties and so i didn't want to tap the coil at 70% 
of the winding to come back to 8,97 kHz but first just to measure out 
where the resonance will be, to solve these open Questions. Of course, 
another important and very interesting issue is propagation in the 46km 
band! :-)

So, sorry for that coarse frequency range. Maybe the actual QRG will be 
written here in the reflector and can be seen on my garbber2 but first 
lets hope for proper WX!

73 and tnx, Stefan/DK7FC



Am 31.07.2010 11:23, schrieb pws:
> Hi Stefan,
>
> Question: do you have a realistic guess of the frequency window of your
> transmission around 6.5kHz, e.g. +-100Hz?
>
> You wrote:
>    
>> ....
>> on *Sunday, the 1. August*, i will make a new kite experiment.
>> ...
>> i will transmit at arround *6,5 kHz,
>> ...
>> Starting time is* 8 UTC*, maybe some time later
>> ...
>> TX QTH is as usual in JN49IS, 49.77647N 8.699525.
>>      
> Distance is 516km, heading 10deg. to Kiel.
>
> Just modified the software running at ~17mHz of resolution. Antennas are
> two crossed ferrite loops feeding some BC550 in parallel buffered by
> NE5532. Both amplifiers are connected to a M-Audio Audiophile 192 running
> at 24 kHz on an Intel Atom 330 "shoe-box" under Linux.
>
> 73 from Baltic Sea,
> Peter
>