W2IRT Writes:
-----Original Message-----
From: Peter Dougherty <w2irt@comcast.net>
To: topband@contesting.com
Sent: Tue, 25 Dec 2007 11:03 pm
Subject: Topband: MFJ-1026 question
Hi all,
I'm just starting to play with my 1026 and I have a question or two.
I'm using a 20' vertical wire as my sense antenna and my K9AY loop as
my main antenna and I'm finding that I can't use the preamp at all if
I'm to get any cancelling on the 1026. My settings arey 7-10-10 with
the invert switch out. I can get rid of the AC line noise on 80 with
it to a pretty good degree but not entirely. adjusting the levels
doesn't do much beyond that point. Is there a way I can use the
preamp and still get noise cancelling out of this?
W2PM Replies:
The noise nulling is no way standardized and the settings completely
unique to your conditions. Amplifying the noise is only required when
the level is too low vs the main antenna signal level - which sometimes
you can adjust by attenuating the main sig level and sometimes by
amplifying the noise - whichever method works is the method you go
with... The biggest issue I have found with noise nulling is the
placement of the sense antenna relative to the "main antenna". The
sense antenna should be fairly close to the main one in order to get a
similar "copy" of the noise. Finding the noise null is very crtical on
these devices - you just have to experiement and find what works. Im
wondering which preamp you are using by the way? The one on the 1026
is typically wired for the whip antenna on the set - which is
essentially useless. I beleive there is a jumper option to use the
preamp on the external sense antenna. Here I use a 1025 which doesnt
have the preamp - and sometimes I use an external preamp for the sense
antenna but most times I don't need it. 73 Pete W2PM
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