[IRCA] Fun with loops again

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

I finally had a chance to do some significant testing with the two five foot
loops.

They were set about 250 feet apart, in reasonably clear spots.  Set in line
aimed about due north. both phased the same.

Two 150 foot coax cables were connected to two DX Engineering preamps, and
then to a home-built phasor similar to a Quantum.  I used the receiver in
the truck, simply because I didn't want to bother dragging the Drake
outside.  I don't think it mattered.

Some stations could be phased pretty well, though others like WCBS-880 could
not.  Interestingly, co-located WFAN-660 could be dropped into the dust.  At
higher frequencies, very little could be nulled at all.  Weird..  Good
pickup from each loop, and both about the same.

Next I moved both loops into the center of the open area and set them at 90
degrees to each other in a "T" position.

Nulls could be had - and deep ones - on many more stations including some
locals.  The IBOC sideband of local WPRO-630 was dropped enough to hear
WNNZ-640 clearly.  They are normally very weak here.  That configuration
seems to be the best way to use these two loops.  I'm considering making a
similar setup and putting it up on top of my tower, rather than a dual-feed
loop and rotor.

I also used the two smaller loops in my truck with the phaser.  They are
already mounted in a "T" configuration, and I had been using a switch to
select the better one for the desired station.  The two preamps before the
phaser seem to help with the nulls compared to a single preamp after the
phase box.  I may buy a third to put after the box to bring levels up again.

So, I'm baffled as to why things didn't null well with the loops set 250
feet apart.  You would think that the two figure-8 patterns could be
multiplied together to form a hypercardiod pattern.  I guess not - at least
until I can work on this again.

Craig Healy
Providence, RI

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