Stefan
I will look for u on 8.87 tomorrow. I use 0.5 mH inductance on 137 kcs with
my antenna and will work out the Inductance to resonate at 9 kcs
de mal/g3kev
----- Original Message -----
From: "Stefan Schäfer" <[email protected]>
To: <[email protected]>
Sent: Saturday, July 31, 2010 10:53 AM
Subject: Re: VLF: DK7FC's 6th VLF kite experiment
> 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
> >
>
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