Hi Frank

Yes the usage of the 1/4 wave section is simple and well known. I have
been doing it for years. The loop Z varies somewhat depending on shape
and height over ground. I am modelling a triangle and it runs around 145r

When I create the "wire" in free space by istelf I get a warning;
Error: Wire 5, seg 91, Ex-src: Not allowed near open wire-end

Mind you it comes up with seemingly the correct result. If I change the
number of segments in that wire from 1 to 3 the error doesnt occur.

More feeling my way at this...

What I'd really like to do is setup a dual band single quad loop (ie one
loop inside the other) for (say) 20 and 40M with no ATU. ie direct coax
feed...

Cheers Bob


Frank wrote:

Bob, I don't know much about quad loops, so not sure what you are doing. Is
the 1/4 wave coax just to transform the single loop input impedance to a
lower value? I think a loop has about 120 ohm input Z, so 1/4 wave 75 ohm
coax transforms it to near 50 ohm.

The transmission lines in NEC are ideal, so you will not get any loss as
with a real transmission line. You do have to have a piece of wire at each
end. The loop end wire is the loop, and the feed point end wire must
contain the NEC source.

Do I have the right idea, or am I completely out to lunch?

Regards,

Frank