From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Fri, 31 Dec 2010 18:49:14 +0100
Thread-Topic: LF: VLF - G3XIZ
Thread-Index: AcupDQ2For9MStzoRFap82qQYUBwygAAnLjo
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Chris, Jim,

congrats from me too.
Based on the locators distance would be 38km (centre to centre locator squ=
are).
About parallelling the balloon antenna and inverted L: as Stefan points ou=
t it would only make sense if you can increase power till you got the same=
 antenna voltage as with the balloon antenna only. At consant power the pa=
rallelling the inverted-L would decrease the radiated power.
Regarding the arcing: a vertical wire has a capacitance of about 6pF/m, so=
 50m =3D 300pF or a reactance of 59 kOhm at 9kHz. Thus 0.2A antenna curren=
t wil give a antenna voltage of almost 12kV !.
Some arcing may be expected at these voltages unless the antenna system is=
 isolated properly. Also the balloons might not like it (and plop).
And before replacing the helium balloon by a parafin powered hot air ballo=
on:=20
1. a hot air balloon has to be considerably larger to get the same lift.=
 Helium has a 3.3 times larger lift capacity compared to hot air. In addit=
ion a hot air balloon has to lift it's fuel, what again lowers the "load=
 capacity".
2. check your insurance if it covers setting you neighbor's house on fire=
 with a hot air balloon. Most insurances do not cover dammage in case of=
 of "foolish behavior".

73 and HNY

Rik  ON7YD - OR7T



________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or=
g] namens Stefan Sch=E4fer [schaefer@iup.uni-heidelberg.de]
Verzonden: vrijdag 31 december 2010 18:01
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: VLF - G3XIZ

Congratulations to the new record Chris, Jim,

What is the exact distance? Some 10 km i think.
http://no.nonsense.ee/qthmap/

Chris, can't you use the inv-L and the balloon antenna in parallel? This
lowers the voltage and needed L, so less losses. And you can make QRO
without increasing the HV problems. If you come back to the same antenna
voltage, you will surely improve the ERP! And the resonance is rather
less affected by the vertical antenna movement due to wind since the
inv-L part stays constant!
If you increase the wire length to 60m (limit in UK) you would increase
the efficiency by up to 50% and lower the voltage by 20%!
Nice success just some minutes before 2011 :-)

73, GL, Stefan/DK7FC




Am 31.12.2010 14:54, schrieb James Moritz:
> Dear Chris, LF Group,
>
> I seem to have a trace on your frequency - see attachment. SNR is
> currently around 15dB with 1.5millihertz FFT resolution. It definitely
> wasn't there before ;-)
>
> Cheers, Jim Moritz
> 73 de M0BMU