On Mon, 8 Nov 2004 10:53:06 -0800, "Joel Kolstad"
wrote:

"Richard Clark" wrote in message
.. .
A 1M loop in a 1Hz field, Hmm?

That was meant to setup the problem such that the loops is electrically
small and such that only quasi-magnetostatic analysis would be necessary.
In actuality I'm thinking more along the lines of WWVB loop antennas --
60kHz.

Hi Joel,

When I was calibrating my Atomic Clock, years distant, my antenna was
a simple 20' whip above the fantail of my ship. We used WWVB and an
unique modulation envelope to perform the job. This didn't make the
antenna particularly efficient, but it was suitably sensitive. Still
and all, there are roughly 5 orders of magnitude down to the 1Hz
region.

You may as well use WWVB as your testbed, or one of the submarine
fleet frequencies around 12KHz. One station is nearby here at Jim
Creek. They use a T antenna of about 1000' tall with a top hat of 6
cables strung between two mountain tops (about 4000 to 6000 feet
between them). The numbers may be off, but you can judge that the
scale is impressive (quite a sight).

Why bother with the complication of shielding?

The idea is that there's a lot of predominently electric field interference
around (60Hz power lines, for ones) and that the shield -- if grounded --
can short out that component of the field and get the loop to respond
primarily to the magnetic field.

1Hz noise field would come from meteors striking, and ionizing the
upper atmosphere. I doubt you could judge against any local sources
of noise compared to that chatter. Given that line frequency would be
6 Octaves away, if you tuned your antenna (it would be tuned, wouldn't
it?), you would have to be next to a noisy power plant to hear it.

73's
Richard Clark, KB7QHC
73's
Richard Clark, KB7QHC