Topband: MFJ 1025 or 1026 Noise Cancellers

[Pete Ferrand]

> 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.

Yes, this point cannot be overemphasized. The main thing to point
out is that the desired signal is not a factor here, but both
channels must have the same amount of noise in 'em.

Also, if the noise aerial doesn't have enough signal pickup,
you'll have to cut the gain down on the main antenna input, which
once you've nulled your noise you may not have enough desired
signal left since you've turned the gain down.


> 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.

This works of course but wears out fingers and pots. I had to
replace one pot in my 1226 already.

It's far easier to just have a couple switches on the inputs that
are some kind of toggle switches that can flip the signal off to
each input in turn for the adjustment. I took an old antenna
switch so I didn't have to drill UHF connector holes and added a
couple automotive-type switches 'cause I had them around and it
works just fine. Each switch just disconnects its input and
grounds the antenna side. An old antenna switch with four coax
connectors already on it makes it easier.

If you want to do it fancier you can replace the pots with push
on/off switching pots on the 1226 itself.

-Pete
WB2QLL
Plainfield, NH





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