[Lowfer] VLF active antenna

[Chris Trask]

>
>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/~christrask/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/