[Lowfer] 8 kHz VLF loading coil idea

[WE0H]

I wonder if Dex is going to do some more 7-8kc loop transmitting this year.
I think he only used 26w and about a 400' long loop. What was that other guy
he worked with (RLD)???

Mike>WE0H


-----Original Message-----
From: lowfer-admin@mailman.qth.net [mailto:lowfer-admin@mailman.qth.net]
On Behalf Of Bill Ashlock
Sent: Sunday, August 10, 2003 4:52 PM
To: lowfer@mailman.qth.net
Subject: Re: [Lowfer] 8 kHz VLF loading coil idea

Jon,

Always exciting to work in unchartered territory!

>I think that the loading coil required at VLF is the most difficult part of
>the whole system, especially making the coil easily tunable.

This would be the easy part from my perspective, although this coil will
have to have a reasonably high Q, maybe 100. Why not use a ferrite coil? You
would have to gap the ferrite to eliminate the saturation tendencies of
ferrite, however. The gap size could be the tuning feature.

How much open land do you have? You will be faced with the typical ground
radial problems and the need to have a lot of capacity in the top hat. ...
and your site has to be pretty free of trees.  No relief from the 'tree
effect' at these low freqs, as the trees still look electrically like a huge
distributed ~10K resistor and any small capacity coupling into them will
kill your antenna current due to reduced system Q.

Have you considered a loop antenna placed over the top of any trees you may
have? I admit that my first attempt at operating a loop at 9 kHz was
discouraging but have some areas to work on before I give up. One of these
includes finding a low-cost, high Q, 10uf resonating cap, or bank, able to
handle some 20A and 400vac. ....That won't bow up. <G> At least the
transmitter is simple.

Good luck!

Bill A

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