[Lowfer] Re: Your un-tuned loop

[J. B. Weazle McCreath]

Hi Tom, Lowfers,

I thought you might be interested in the alternate feed
arrangement that I'm currently trying on my big delta
loop for 500 kHz.  I had been using series tuning and
a 4:1 turns ratio step-up transformer to couple to the
RG-6U feedline.  It works fine on the frequency that
it was tuned to but left a lot to be desired if I moved
away from that frequency.  I want to do some NDB
work and hence need a broadband antenna/coupling
arrangement.

I measured the loop's inductance to be 200 uH. and then
calculated the inductive reactance over the frequency
range that I wanted to cover.  The calculations showed
that a 2:1 turns ratio step-down transformer would give
a reasonable match to the feedline.  I wound one using
a binocular core with 16 turns on the antenna side and
8 on the feedline side.  It's reactance is much larger
than the antenna's or feedline's.

This seems to work pretty well, at least in the time I
have been testing so far, but the lack of selectivity
does show up.  I'm thinking of trying out an in-shack
tuning setup similar to M0BMU's "lazy loop", but will
my matching transformer give me trouble?  In essence
I'd be doing the tuning on the feedline side rather
than the antenna side.  Any comments are welcome.

73, J.B., VE3EAR - VE3WZL
Solar and wind powered
Lowfer " EAR"  188.830
EN93dr

http://www.hurontel.on.ca/~weazle