On 19 Jul 2011 20:55:42 GMT, Allodoxaphobia
wrote:

In BCB SWLing you want the null(s) deep (and steerable)
to kill the strong, unwanted station.

This characteristic demands the SAME considerations as required for a
sharp beam of high directionality.

If we were to select the antenna that matches your quoted specs above,
it would be called the Cardiod (example available in EZNEC). Problem
there is the 30dB null isn't steerable (not enough elements). And it
is large (too large for the back yard):
1. Too tall for most to build.
2. Elements too far apart (out of necessity for, dare I say it?
Phasing).

As it is designed as a transmit antenna, too tall is quickly
dismissed. You can use as short of one as proves useful.

The first element, now being shorter, also allows us to add any number
of shorter elements in an array around (or mixed in with) the first.
This brings steerability. The more elements, the better angle
resolution and null depth control.

You can pull the additional elements (if only one more to build a
proof of concept Cardiod) closer to the first (dismissing the large
spacing objection), and introduce the necessary time/phase control
through:
1. cabling;
2. analog delay circuits;
3. digital delay circuits.

Moving to a digital solution controls all variables.

If none of this is covered in the "Dallas Files," it would be best to
leave them in the File Cabinet. Jim has provided adequate links to
fill in the gaps and no one was injured in the process of obtaining
the information.

73's
Richard Clark, KB7QHC