RadioBanter - View Single Post - Distance to Link Coupling in a Loop Antenna

October 27th 03, 10:46 AM

wrote in message ...

All input will be greatly appreciated. Thank you.

I just varied the coupling loop around a bit , and noted the highest
signal level. You can do some distance testing with just a small
portable radio with a ferrite antenna, if this were for MW. For HF,
I'd probably use a single turn loop for appx distance testing, and
then when I found that, I would vary the number of turns to see which
was best. I used two turns on mine, but even a single turn gave enough
level to be perfectly usable. I found it was not overly critical, and
I have plenty of signal strength even without a preamp. I think I
actually had more signal going direct to the main loop, with no
coupling, but I saw a better pattern using the coupling loop. I saw a
little skewing of the nulls off the true direction of the loop when
using a direct feed. But that could be partly a common mode problem
also, I suppose. I use no impedance matching or even a balun. Just a
short run of rg-58 to my radio. I still get very deep nulls. The use
of the coupling loop seems to act as a sort of psuedo balun in my
case. It corrected the skew.. Have plenty of signal for my radio, so
see no need for further matching, or a preamp in my case. Mine is a
16 inch round loop, 12 turns, and the coupling loop is 2 turns about 1
inch away from the main loop wound on the same form. With the cap I
use, it tunes 500-2000 kc. It's mainly for MW, but I can also use it
for 160m. I can drop into LW, if I clip more fixed capacitance in
parallel with the main one. MK