On Aug 14, 10:27 am, Ron Hardin wrote:
Steve wrote:

I noticed this on the Wellbrook website (http://www.wellbrook.uk.com):

The Wellbrook Phased Array is a totally new receiving antenna designed
for optimum MW reception. This Antenna system is only Broadband Phased
Array to offer a uni-directional pattern similar to the Beverage, over
360 degrees with electronic Null Steering. The design is the result of
several years research by Wellbrook's owner and chief design engineer
Andrew H. Ikin. Trials of this new array have been performed in the US
by experienced MW Dxers using the phasing system with high performance
Active Vertical and Active Loop antennas.

These trials demonstrated that the Phased Array equipped with elements
made from ALA 100 Large Aperture triangular Loop Antennas (one of the
world's best active antennas) provided much lower noise and improved
side rejection than an identical array equipped with Active Vertical
antenna elements. This finding was particularly important for DXers
living in urban areas. Moreover, comparative listening tests indicated
that the Phased Array was equally as sensitive and directional as a
1000-1500ft Beverage, with the added advantage of deep null steering!

Phased Array Design: The Phased Array provides a reversible uni-
directional reception pattern similar to a 1 wavelength Beverage with
the added ability for the user to steer up to 50dB nulls around the
back of the array.

The Phased Array consists of a Control Unit and two ALA100 Loop
antennas. Each loop is triangular with just one support pole. The
Phased Array can be expanded to use four ALA100 loop antennas to
provide 360 degree coverage.

The Control Unit combines the output of the two antennas using a
technique known as "Delay line Anti-phasing" i.e. the antennas are
combined in anti-phase plus a Variable Delay-line equal to between 50%
and 100% of the spacing of the antennas. This phasing technique
provides a uni-directional reception pattern over a very wide
bandwidth with only a minor adjustment to the controls.

This has a considerable advantage over the majority other phasing and
noise cancelling systems which require constant adjustment even with
small frequency changes.

PHASED ARRAY KEY FEATURES

Uni-directional pattern similar to the Beverage

Simple to erect (no control Lines)

High Front to Back ratio and side rejection

Up to 50dB null steering

High dynamic range amplifiers IOP3 +42dBm; IOP2 +75dBm

Very low noise ALA100 loop antennas

Lower noise than Active Whip arrays

360° with 4 Loops

12Volt DC power, ideal for Dxpeditions

Only requires 40m antenna spacing

I use 2 ALA1530s (along with 6 Dymek McKay active whips) in an 8-element phased
array.

One unpleasant fact about phasing with two loops is that you can't get a good null
at broadside, that is, in the area already in the null of the loops.

The reason is that a very slight deviation in the angle of arrival of the unwanted
signal reverses the phase of the signal, and so your phasing is completely wrong
for getting a deep null on that signal.

Paradoxically, the best null comes from pointing both loops at the unwanted signal,
which gives the most stable signal phases ; except that the adjustment has to be
finer and finer the stronger the unwanted signal is, and so a compromise is usually
more workable, pointing the loops a little at the unwanted signal enough to stabilize
the phase, but not so much that the signal strength is raised hugely. The more stable
the direction of arrival (say it's a local), the further to broadside you can put the
unwanted signal.

Anyway, there's trouble eliminating signals at broadside by adjusting the phasing,
with loops. No such problem comes up with whips.

A better deal all around is phasing a loop with a co-located whip, which gives
360 degree coverage with zero antenna spacing.
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I phase my ALA-330S with a PA0RDT Mini-Whip. The mini whip is really
just a noise antenna, but it's a good one.