[Premium-Rx] Super ferrite rod aerials

[Ben Dover]

Funny you should mention monster ferrite antennas.

After working with air core loops for a number of years, I've been working
with a monster ferrite design of my own here for the last six or eight months.

I've been going for LF and VLF coverage, and the air core design model hits
a brick wall re. practical dimensions for amateur designing at about 100 KHz.
The additional permeability of a big ferrite core makes things a whole lot
easier mechanically, and makes very efficient VLF recieving antennas a quite
practical proposition.

I won't go into a whole lot of detail here, but my designs are based on a LOT
of toroid cores stacked to make a BIG ferrite rod...   say, 3 to 8 feet in
length and over an inch in diameter. The basic loop design uses a low noise 
FET preamplifier (perhaps 25 - 30 DB of gain). A lot of it's structural design
is based on PVC plumbing fittings and pipe. Except for the tedium of winding,
construction from scratch is easily done with hand tools, plus the usual PC
board work to build the preamplifier.

So far, I've built two of them successfully. With a 60 - 2200 pf variable
cap for tuning, the first went 20 - 100 KHz, and the second (still in the 
late stages of construction) tunes roughly 7.5 - 24 KHz.

If anyone is interested in them, my Yahoo group, LF / VLF HANGOUT, has some
messages from me with detailed information on the antennas, as well as a lot
of pictures made during construction as well as the finished product.

If you don't want to join Yahoo groups, E-MAIL me off the list and I'd be
happy
to send you the picture files, and answer any questions you might have.


73's,

Tom, W9LBB




At 10:26 AM 8/3/2005 +1000, you wrote:
>I recall seeing a monster ferrite aerial in the LWCA magazine pages some
>years ago, made of "a lot" of smaller rods glued together. It was rotated on
>a small trolley and was reported to work quite well. It was several meters
>long and I think about 2" in diameter. You might need to find a closeout
>sale to match this !!
>I have made several smaller composite rods and they all exceed single rod
>performance.
>Rick
>
>
>
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