[Elecraft] SGC-239 vs KAT2

[Stuart Rohre]

What we all overlooked mentioning, depending on coupling and height above
the apparent RF earth, a loop is about 200 ohms when opened to feed it.  Of
course, that is up in the clear, and it will lower in the attic.

Thus you have (ideally),  a four to one mismatch with 50 ohm short coax.
Now, you might do better with a one quarter wave of coax, but that is a
single band solution.

Fundamental here is the SGC is an unbalanced transmatch as most autotuners
are.  The loop is balanced and wants to be fed balanced.  Coax is
unbalanced.  Yes, it can work, but adjusting the length of coax can move the
problems away from the transmatch attachment point, and may help a less than
ideal solution to work acceptably.  Other RF decoupling schemes may also
make it work acceptably.  At QRP, you can often make a go of it, even if
less than ideal.  The loop will be more conventional in behavior at 20m and
up with this length.  However, should be workable on 40m, with care.
73,
Stuart K5KVH