[Milsurplus] Ferrite Loop Antennas

[Thomas Adams]

At 07:44 AM 12/10/2007, Brooke Clarke wrote:
>Hi Hue:
>
>They have small effective areas so are not optimal for weak signals.
>
>The attic antenna descrebed by J Forster sounds good.  It might be 
>improved by spacing the wires from each other about one wire 
>diameter to lower self capacity.  Reasonating would give you a nice 
>high Q antenna.  A problem might be the nulls.
>
>Have Fun,
>
>Brooke Clarke


Howdy, Brooke.


Yes, ferrite antennas for VLF are indeed possessed of a very small 
aperture, and are far from optimal for weak signal work.
However, there's other things to be considered here.

Ferrite loopsticks, especially when shielded, have a VERY low noise 
floor. That's a big help.

Also,  a tuned loopstick has pretty high Q, which in itself is an 
effective noise limiter.

I've been experimenting with very large loopsticks for a couple of 
years now, especially designed for LF / VLF use. My
largest is about 7 feet long, and tunes 7 - 23 KHz . The ferrite 
cores are made of stacks of identical toroid cores strung
on lengths of PVC pipe (I came up with a CASE of  large, low 
frequency toroid cores for almost nothing).


I've found these things to be quite effective on VLF really; the most 
effective antennas I've ever used for that frequency
range. You can see some pictures, and read about my design and 
experiments, in the message base of my Yahoo
VLF group, LOWFREQUENCY   http://groups.yahoo.com/group/lowfrequency/


Mr. T., W9LBB