[Lowfer] LF receiving loop

[Zack Widup]

I finally got done with a project that has taken me a couple years in my
"spare time." I made a 20 turn LF loop, 5 feet on a side, with turns spaced
1 inch apart on a pvc "X" form. And I built this remote tuner/preamp:

http://www.lowfer.us/k0lr/preamp/preamp.htm

It's the second schematic, with the four varactors, that I built. I used
MVAM109 diodes. I also added a set of switchable parallel capacitors to the
circuit. allowing me to add capacitance from 100 pF to 6400 pF in powers of
2. I also placed taps on the loop, at 3, 5, 10, 15 and 20 turns so I could
select smaller inductances.

I got around to trying it out last night. I was not happy with the results.
The tuning appears to occur where I expected it based on some calculations
I made. But the signal strength is on the weak side. I tuned part of the AM
band and saw signal strengths far below what I'd hoped for. Only a coupe
local stations moved my s-meter. I am getting stronger signals from an HF
vertical (MFJ 1796).

I am using 100 feet of Micro-8X coax cable between the remote tuner box and
the receiver in the shack. I don't know if that's part of the problem or
not.

Does anyone have any experience with this?

73, Zack W9SZ


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