Al wrote:

I have used Reg's fine loop design program rjeloop3 to help me with building
a couple of loops. It was a big help. Thank you Reg.

The shielded three-foot diameter loop I built is for receive only. The
primary loop is six turns paralleled by a variable capacitor, and the
secondary (link loop) is one turn (same diameter) fed to a preamp or
directly to the receiver. The band of operation of the loop is about 200kHz
to 500kHz (NDB chaser).

One question that is not answered in rjeloop3 is what should be the distance
from the output (link) loop to the main loop? The antenna's I built used
flat cable for the wiring and one of the turns was the link so the distance
was 0.050 inches. In other articles I have read that the Q, gain, and S/N
ratio can be varied by varying the distance between the two loops.
Approximately what is the distance? Are we talking a small fraction of an
inch or 2, 3, or perhaps six inches apart? I would just like a feeler
distance to work with. If the distance is to be over one inch, I'm
considering building the primary loop in one hoola-hoop form and the
secondary loop in a second hoola-hoop then varying the distance between the
hoops. Any thoughts on this or is this a waste of time and effort?

All input will be greatly appreciated. Thank you.

Al
KA5JGV

I don't know if this will help, but perhaps you can adopt
the idea to your loop.

I built a receiving mag loop for 40 - 160 as follows:
Using hardline, I stripped the ends so the center conductor
stuck out about 1 inch on each end. I made the outer loop
out of it - it is ~4' in diameter. It is open at the top, and
a variable capacitor (900 pF) connects the two ends on the
shield of the hardline. (I switch in another 1650 pF for 160).
Inner loop is made from 52" of the inner conductor and
insulation of RG8 and is mounted at the bottom. The two ends
of the inner loop connect to the SO239. At the top of the
outer loop, the copper inner hardline conductor connects to
a 1N4148 with 1K in series and a 1 mA meter. When I excite
the inner loop with my MFJ 259B, I tune for minimum SWR with
the variable cap. The 1mA meter goes to maximum when the SWR
goes to minimum.

Ok, now to the coupling. The inner loop can be maneuvered
for maximum reading on the 1 mA meter. I found I get the
highest reading on the meter when I squash the inner loop
into an oval, decreasing its vertical diameter to about
1/2 what it was when it was a circle. I taped the inner
loop to the outer loop to hold the shape with the maximum
coupling. Perhaps some variation of this technique can
be used on your antenna.

I'm still experimenting with my loop. The tuning on 40
is difficult - I need a smaller variable cap. I plan to
try switching out 450 pF of the variable (it is currently
2 450's in parallel), and switching in some series fixed C
to see if I can cover 40 with a 180 degree rotation of the
variable - right now a few degrees of rotation of the
variable makes a very large change in the frequency.