Topband: MFJ-1026 Noise Cancellation

[Tom Rauch]

> What absolutely will not work is having the signal to
noise power ratio
> and phase relation exactly the same on both the main
antenna and the
> noise antenna. In that case whenever you adjust to cancel
the noise, you
> will also cancel the signal.
>
> So making a noise antenna with the identical directional
characteristic
> of the main antenna is probably not going to work.


This is a complex topic and difficult to get across in a few
words, but two identical pattern antennas will work quite
well if the unwanted noise or signals and the desired signal
or signals have different phase or level relationships in
each of the two antennas.

If the unwanted and wanted signals both have the same phase
and level, it will not work. That doesn't mean the antennas
have to be different. What it means is if the desired
signals arrive exactly in the same phase and level
relationship in both antennas, and the undesired signals
also arrive in the same  phase relationship in both antennas
(even if different than desired signal phase) it won't work.
That usually requires one antenna for both ports.

What would work or not work would make a good article or
chapter in a book , so the easiest thing to do is try it.
One good rule is the sense and main antennas must hear the
same noise and the noise must not be from the same arrival
direction as the desired signal or it won't work.

There are some detailed well-written Internet articles about
noise nulling that have been out a long time that are wrong.
I haven't read the recent articles posted on Topband because
of my work load. I'll probably be able to read something in
July. ;-)
73 Tom