WG: LF: VLF_8.79 kHz

[Stefan Schäfer <schaefer@hst.tu-darmstadt.de>]

Pete,

 

Yesterday in the night or today in the morning i had another idea. The mail wasn't reflected, perhaps too much data volume (sri, have forgotten to delete the old mails hanging on)

 

73, Stefan/DK7FC

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Von: Stefan Schäfer
Gesendet: Di 23.02.2010 01:35
An: rsgb_lf_group@blacksheep.org
Betreff: AW: LF: VLF_8.79 kHz

Pete,

 

A last idea for today (PC was already shut down but i cannot slep now ;-) ):

 

The very simpelst, maybe not the worst, way to try it on VLF is using your inv L antenna as a real vertical loop.

 

That means you could try to take a wire and connect it to the end of your L, place it on the ground back to the feed point. Then, all you need is a C, probably some 10 µF, to compensate the L of the wire at that frequency. The current will be limited just by the resistance of the antenna wire, and the power of course. There will be no loading coil, so you reduce much work!

 

Perhaps the overall resistance will even be in the region of 4 Ohm, so you do not even need a transformation! Just connect the ground wire to the ground of your amplifier and the top wire of the antenna in series with the C to the AF output and adjust C for maximum antenna current (e.g. measured by a 0,1 Ohm shunt resistor and an oscilloscope). That could be done in 1...3 hours of work :-)

 

If your signal will be received in 6,5km, you could tell us the difference to the before mentioned ways of matching. And: Since Jacek has reached 750m with 2W TX power and a 4m*14m loop, you could be successful with 100W and a vertical loop with more area and QRSS...

 

GL!! Stefan/DK7FC