[IRCA] Another directional antenna array

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

I've been experimenting with a different antenna setup.  It's a combination
of a loop and vertical.  In this case it's a large ferrite loop antenna and
a balanced vertical wound on a length of PVC pipe.  The two antennas are
combined in a unit with two potentiometers and a 0 or 180 degree switch.
There are two bifilar wound 1:1 transformers and a trifilar wound 1:1:1
transformer used as the combiner.  All on ferrite toroids.  No phasing
components.

The loop and vertical are mounted within a few feet of each other.  The
vertical is fixed position while the loop is rotatable on a camera tripod.
It really is a simple arrangement.

To use it, the pot for the vertical is turned all the way down and the loop
pot all the way up.  The loop is rotated to make the best null of the
undesired station.  Then the vertical pot is turned up to lower the null.
If the signal raises, then the 0/180 switch is flipped.  Most times the
vertical is less than 100%, though occasionally the loop is turned lower.

This has made very deep nulls on stations that have been very hard to null
in the past.  For example, even using a good quality commercial phaser, it's
been hard to null the local 550 station.  This can knock it down to
essentially inaudible.  The nulls are fairly broadband as there is no tuned
circuitry in it.  All broadband.

These are indoors and within a few feet of a computer, so it's somewhat
noisy.  The antennas can be configured to minimize the noise.

Only a single DX Engineering preamp is used between the combiner and
receiver.  It brings the signal up to very good level.

I'll be doing some further work with this.  It has some potential.

Craig Healy
Providence, RI


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