Your VLF work is the most interesting project! I saw all your info on the web. I guess there is nowhere else for you to go as you went down to 4 or 5 kHz. There must have been some voltage there on that coil!!
I wound my loading coils with number 12 insulated copper solid wire. Was available from contractor friend as they use tons of it as a tracer wire when they lay plastic water and sewer lines. The coils run very cool in fact just a very small temperature increase and it takes a few hours of operating to notice any heat in them. I wound them on sewer pipe [6" PVC] that was scrap pieces from my contractor friend. I don't know where all the losses are but probably in the ground and surrounding tower and one tree near the tower.
I noticed on 500 that the series loading coil is about the same amount of inductance as what is in the pi-net tank.
As you had mentioned my 500 signal is fine. Even on 137 the amount of inductance required in the series loading coil is not a tremendous amount more than what is in the pi-net tank but more in proportion to that required on 500 which indicates more top load or taller tower would help the field strength significantly on 137 as well.
When it comes to 73 kHz I had to add allot more inductance and some "C" to ground to hit resonance. I will show you a pix of the coil arrangement and the large amount of inductance required on 73. It is certainly due to lack of "C" and more top load would help greatly-I have to figure a way to add more top load-as many top load wires as I can fit.
Date: Thu, 26 Sep 2013 13:49:10 +0200
From:
[email protected]To:
[email protected]Subject: Re: LF: TA CW?
Am 26.09.2013 02:50, schrieb Bob Raide:
Stefan;
If you get time can you show me where the sphericas electrode would be
placed? Maybe at the ant end?
Add it where you can see it sparking. You can use more simple
arrangements to prevent arcing though.
But preferably i recomment to increase the top load capacity of the
antenna. This will reduce the voltage and the coil losses. The coil
losses could be in the range of 30 to 60 % of your total losses i guess.
I have figured you have 10 db on me on 137! You are
in here almost every night regardless of conditions!
That is nice. I hope i can hold this situation as long as possible. But
they are building another building in 30m distance of the antenna. This
will not improve the situation :-( Sometime everything comes to an end,
we know.
I see pictures of your 9 kHz gear and the land is flat
and I would bet your soil conductivity is very good.
The 8.97 kHz experiments were done at a different location. This
location was excellent, until they installed a 2 MW wind generator
there. All experiments were /p, so i had no permanent earth system
installed there. I used a long copper plate and a few earth rods on
VLF. I a short experiment i transmitted in CW and so i had to add a C
of 60000 uF (350V) to the PA, so the generator just sees an average
power. There i got 1.7A antenna current on 8.97 kHz in a 300m vertical
antenna. The signal was audible in 40 km distance which is more than 1
Lambda. More could have been possible but there were no listeners in
that sort of distance. But in DFCW-600 i managed to be visible in 4X,
TF, EI, G, F, ON, PA, SP, OE, I, OK and YO. Nice to think back to these
times :-)
73, Stefan/DK7FC
