[IRCA] Loop work

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

I've done a bit more work with trying to get a small, phase-capable loop.
It's the first pass on this, but it's encouraging.  I added a second toroid
pickup to a 3' copper loop and moved them to adjacent corners.  In the past
I tried putting one on top and another on the bottom, centered.  That did a
virtual tilt of the loop to maximize the null and worked well.  It also
required turning the loop to get the initial null, however.

This is able to get a null without moving the loop at all.  It does seem to
null best off the ends, but will still get a useable null over 360° by
phasing.

All I did was lean it up against the wall just as the first picture shows.
Pickups on the top two corners.  Using the DXE phaser, the SDR showed at
least a 40db null on every station I tried.  It does require a fair bit of
preamplification, as it's small and has little efficiency.  The DXE phaser
could use a vernier balance control as well.  It's very touchy.

Electrically it's just a miniature of a larger loop type that has two
pickups in the lower corners, IIRC.  The difference was that the large one
is adjusted with a pot and not a phaser.  I haven't tried a pot on one of
these yet.  Not sure it would do all that much, but, worth a shot.

Here's a shot of the loop and a closeup of the corner.  Not much to it,
really.  Just a toroid over the copper and six turns of #14 wire, twisted.
I have those looped through a Radio Shack clip-on choke, but it probably
doesn't matter.

http://www.craighealy.com/superloop_copper.jpg

http://www.craighealy.com/loop_corner.jpg

Whan I get time, I'll work some more on it.  Next effort will be to string
up a much larger loop of at least #10 gauge wire, maybe 20' by 50' and use
the toroids in the lower two corners.

Craig Healy
Providence, RI


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