[Lowfer] VLF active antenna

[Zack Widup]

Wish I'd gotten all this info while it was still warm outside! I've had it
in the corner of my mind to put up one of these active antennas but never
got around to it.

There are two places on my property where it would work out (where I can get
the active antenna high enough). One is on the top of a wooden support for
my 40 meter full-wave vertical loop. The other is on a metal pole on the
other side of the house that is a support for one end of an 80 meter dipole.


I can lower the 40m loop to put it on that but would rather do it when it's
a bit warmer. Also, that location places it about 10 feet from a power line.
The other pole I cannot get to without a 30-foot ladder, which I don't own
but borrowed when I put it up.

Maybe I can get my LF loop working better.

73, Zack W9SZ


On Thu, Dec 16, 2010 at 7:11 AM, Chris Trask <christrask at earthlink.net>wrote:

> >
> >Objective:
> >
> >Construct an active "e-probe" antenna that is sensitive well down into
> >the audio frequencies (1 kHz or so) up to around 30 kHz, that can be
> >fed with a run of 50ohm coax into a receiver located in the shack.
> >
>
>      Here's the design I came up with a couple of years ago:
>
> http://www.home.earthlink.net/~christrask/Paper007.html<http://www.home.earthlink.net/%7Echristrask/Paper007.html>
>
> http://www.home.earthlink.net/~christrask/Paper005.html<http://www.home.earthlink.net/%7Echristrask/Paper005.html>
>
>     Using the amplifier of Fig. 5, one fellow changed the coupling
> capacitors to 1.0uF and got a bandwidth of 10kHz to 200MHz.  I'm working on
> a similar design that may have better IMD performance.
>
> >
> >It occurred to me that a "natural radio" front end might be a good
> >choice. Here is what I came up with:
> >
> >http://i81.photobucket.com/albums/j231/Goranothos/VLFantenna.jpg
> >
>
>      I'll have to dig out the whistler receiver I was working on years ago
> and see how far down it will go.  It's a 2-stage tranformer-coupled
> low-noise push-pull design.
>
>
> Chris Trask
> N7ZWY / WDX3HLB
> Senior Member IEEE
> http://www.home.earthlink.net/~christrask/<http://www.home.earthlink.net/%7Echristrask/>
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