Hello, John Bryant! A few words on my quick tests.


sloshatron <wa1gwh@...>
 

Well, I did purchase a digital camera a while back but have not
gotten around to putting the software on the PC and figuring it out.
So, for the time being, no pictures are available.

Actually, not much to see! A 4.1" diameter by 1.2" long basket weave
solenoidal air coil vs a surplus ferrite bar with #20 PVC solid
hookup wire wound close over the center half. And a ceramic
insulated variable.

The ferrite bar was picked up at a ham swap table for a few bucks.
It used to be mounted in a plastic housing with a central pivot and
looks to be for some sort of direction finding rig. It was in a box
that appeared to fit it and be the right one. The labeling on the
box said "ANTENNA SUBASSEMBLY AN/ARN-59". There are all kinds of
alpha numeric codes on the label and a bar code (no pun intended).
There is a field that appears to be a date, "02/90". An internet
search led me to believe the unit covered 150-1750 kHz. So this bar
is likely good for MW. It is pretty chuncky at 4.8" long by 1.25"
wide by .42" thick. I'm not especially into ferrite bars, but for a
few bucks I could not resist.

I'm going to see about picking up some 4 conductor telephone cable to
get the #24 insulated wire it is made up of. I will then rewind the
ferrite bar to what I think is a higher Q format with the winding
spaced about 1/8 inch off the bar and the turns occupying a centered
position and taking up much less length of the bar with the smaller
gauge wire and thinner insulation. This will be an easier wind than
space-winding and will give some wire spacing due to the insulation.
Not optimum but quick and easy. Then I'll have another check against
the basket weave air coil. This will again be as an external booster
antenna. I figure that results for a booster antenna will likely
correspond to a transplant.

Not sure where I'm going with this. Just messing around a bit.

By the way, I think that paralleling bars approaches the performance
of thicker bars. I remember reading an article in an ARRL Radio
Amateur's Handbook about paralleling bars to increase sensitivity in
a 160M ferrite bar loop antenna for receiving.

Also, a fairly recent discussion on the Xtal Set Society forum
mentioned bars used end to end. If I remember correctly, results
were best with about a paper's width between the bar ends. But you
are already using bars end to end, John! (Have you looked into
cutting notches into both sides of your doorways yet?)

I'm not sure how paralleled bars stack up (oops!) against end to end
bars in performance. I will dig out the ARRL Handbook article and
report back.

Best Regards,

Garry
near Syracuse, NY