Topband: MFJ 1025 or 1026 Noise Cancellers

[NR1DX]

The trick with any of the noise cancellers is to get a (noise) signal of
equal amplitude into both the main antenna input as well as the noise
antenna input. In my experience folks who have had problems getting the
cancellers to work have not put enough thought into getting a good antenna
for the "noise" antenna. For example If you look at the relative efficiency
of a full size inverted L on 160 vs say a 10 ft piece of wire or the 1'
whip that comes with the canceller it doesn't take much to figure out that
the ability of the smaller antenna to pick up a noise source a few blocks
away may be down by as much as 60db as compared to the larger antenna. A
20db preamp in the MFJ1026 won't make up the difference enough to get a
good null, If the source of noise is a leaky pole pig in your own yard the
small noise antenna may do it. The procedure I use with my 1026 is I first
note the s-meter reading of the noise with the "main antenna gain"  all the
way up and the noise antenna gain all the way down. I then turn main
control to zero. I then turn up the gain of the noise antenna until I get
the same s-meter reading. Next I turn the main antenna gain all the way
back up and adjust the phasing control for a null. Careful tweaking of the
noise gain and the phasing control then tames the beast. If I can't get an
equal level through the noise antenna side. I either live with the noise or
try a different antenna as the noise antenna.

Successful noise nulling is an art and it takes a good noise antenna plus
patience to tune out a noise source as the controls can be quite sharp.
Also if you are dealing with more than one noise source your out of luck as
the noise canceller can only get rid of one noise at a time as the
arriving phase of the two sources is different. 

Dave NR1DX




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