Re: VLF: DK7FC's 6th VLF kite experiment

[Gary - G4WGT <g4wgt@tiscali.co.uk>]

Mal, LF,

I will be watching for Stefan on 6.6kHz +/- 200Hz (not 8.97kHz as you keep stating) as you may have read in his mails. I will be using a loop & pre-amp as designed by Jim M0BMU.

Battery is now fully charged & system ready to go.

73

Gary - G4WGT.

On 31 July 2010 16:35, mal hamilton <g3kevmal@talktalk.net> wrote:

Stefan
Who has a RX setup that will be able to look for your signal, I seem to be
the only one so far. There is a trace on 8.97 at present but noone else can
see it.
There is very little response via this reflector and vy little acty at
present on 137 and 500.
de mal/g3kev

----- Original Message -----
From: "Stefan Schäfer" <schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
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
> >
>