Sounds like you have made your own variometer
In the case of a loop antenna it is a coupling of two circuits each
having resistance, capacitive and inductance .Each of these values
have two forms,
reactive whuch means that it is a combination of two reactive
components and in the case of resistance there is real resistance and
radiative resistance.
You can insert distributed loads for each of these components or vice
versa
so that these two circuits can be made into one circuit by capacitive
or inductive coupling means.( read up on solving complex circuits)
Obviously the inductive coupling values will change along with the
other loads so the use of a variometer helps to not tie one in
absolute terms of inductance coupling to the thickness and length of
material used which is representitive of distributed loads as well as
losses.
If one chooses compatable material thicknesses for a 50 ohm impedance
one can physical connect both circuits which is a inductive coupling (
you can also do capacitive coupling) and thus use only the variable
capacitance for what will be a limited total band spread.
Remember that when designing any antenna it is to get maximum current
flow
So the introduction of TWO radiating circuits gives you extra leverage
to obtain this. If you are sufficiently skilled then you can add a
series of circuits and thus obtain efficient radiators with a
controlled input impedance while choosing what circuit has the high
current flow as well as selection of any individual bandwith.This
should explain why physically coupling two loop circuits can restrict
choice to determine what is required as opposed to your choice to be
able to change the coupling mode which gives you more choice for
better options.Increased variations and design changes for ultimate
rotational design of antennas for any frequency without being bound to
wavelength which will soon be available via the PTO.
Good luck and please keep us informed of your progress
Art Unwin KB9MZ...XG



wrote in message ...
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.