Re: [IRCA] [am] Fun with loops

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

Addendum to recent work:

I received the new ferrite toroid samples.  The FT-240-77 seems to work at
least as well as the unknown toroids salvaged from the Harris transmitter
card.  So, anyone can duplicate my results with that part.  There may be
other toroids that are better, but this is Good Enough.  Works down to
longwave, and seems to work up to at least the 40m ham band.

The parts arrived to build the combiner box to mix the outputs of two loops
mounted 90° from each other.  So far results aren't too good.  Some nulling
is possible, and in one case enough to walk a null around to knock down
adjacent channel splatter from a local.  However, not good enough that I
would recommend anyone go out and build a copy.  I have a few more things to
try, including use of a Quantum phaser to see how that works.  It just
hasn't arrived yet.  This is all very much a work in progress.

Another thing on the to-do list is to make a modified version in the form of
a flag antenna.  I'll make a 5' by 10' loop with the longer sides
horizontal.  Then cut the 5' vertical sides in half and insert a fiberglass
insulator.  On one side I'll put in a matching transformer and the other
side a variable pot.  I have a number of 500 ohm conductive plastic pots and
some fixed resistors.  I will see just how small a flag can be made and
still exhibit a cardiod null.  If that works, then the next logical path is
to try making a second and phasing them.  Or, phase against a loop.  Or
simply mount it on a rotor.

I'm especially looking forward to trying the Quantum phaser with two five
foot loops I have.  The idea is to set them up in opposite corners of my
yard aimed roughly north-south.  Then phase the two to null things off to
the north or south.  The side nulls won't be exact, of course, but should
provide some inherent reduction of signals from NYC, Chicago, etc.  Then the
phasor can pull down the stuff from Boston or Canada.  Spacing from loop to
loop will be at least 250 feet.  I have enough coax to run that distance.  I
will have two DX Engineering preamps as soon as the second arrives.  Maybe
in today's mail.

It seems my mailman is named Godot..

Craig Healy
Providence, RI


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