http://www.lwca.org/library/articles/ywk/octoloop.htm

http://technology.fanshawec.on.ca/elec316/rigs.htm

http://technology.fanshawec.on.ca/eltn124/leeloop.htm

These sites are oriented more towards the "ocotoloop" than the
multi-turn loop you are using, but might provide some food for
thought.
I have used them for the past eight years. At present I have a 10 foot
"octoloop" and a 16 turn remotely tuned loop ( using varactors ) and
switch back and forth. I find the "octoloop" to be trouble free here.

The major advantage of the "octoloop" is that it tunes from approx 10 kHz to 500 kHz
allowing me to do lots of NDB work, and the 160-190 kHz and also the 137 kHz
band - without tuning  - and they work prefectly.
I use the Burhans preamp and it is excellent - I have sent them across the
country ( even to Steve  VE7SL )
Copied Steve every night on our 137 kHz trials, and also the New Zealand station.

If you're interested, I have a 7 foot octoloop, which has been gathering dust
in the back shed for a year or so.... it has preamp and is ready to go. I can throw
it on top of the car and deliver if you like. It's for free!
My son is in Bayfield so it's also a good chance to visit - ! ! !

Let me know

73

Mitch  VE3OT  London