There are other magloop programs beside mine.

Most of the others calculate the size of the tuning capacitor in pF to
be that which resonates the calculated loop inductance in
micro-henrys.

This is incorrect.

It may be OK for very small loops. But, taking the extreme example.
when the loop circumference approaches 1/2-wavelength at the working
frequency, obviously no more capacitance is needed regardless of the
value of the loop inductance.

But if there is no capacitor then the loop cannot be tuned precisely
to resonance! A variable capacitor, with its minimum stray
capacitance, is always needed. The inductance being somwhat less than
the theoretical value.

It is popularly assumed that the diameter of the small coupling loop
must be 1/5th of the diameter of the main loop. Actually this is a
rule of thumb and, for an accurate impedance match, the diameter
changes somewhat with frequency and the conductor diameter of the main
loop.

But 1/5th diameter applies only when the impedance to be matched is a
50-ohm coax. Other feedpoint impedances need a different diameter. The
diameter of a 75-ohm coupling loop should be about 1/4 of the diameter
of the main loop.

It is common practice to screen the coupling loop by making it from
coax cable. This is a waste of time and materials. No useful purpose
is served either on receive or transmit.

The coupling loop can be a self-supporting circle of wire of no
greater thickness than the inner conductor of the coax cable which
serves it. It can be a square or other loop of the same area but a
circle is neater.

It is best to make no direct connexion between the main and coupling
loops. Isolate the main loop from the feedline and everthing else.
Although this may be difficult to do when there are control wires for
a motor-driven variable tuning capacitor. Chokes can be used in
control wires or bundles of wires.

Just a few hints and tips which come to mind.
----
Reg.