In a message dated 1/21/2006 8:12:17 AM Eastern Standard Time, tod@k0to.us
writes:
Because of a sudden appearance of a line noise I had to get out my MFJ-1026
and set it up to cancel the RF intrusion while I wait for the power company
to replace the defective street light in a subdivision to the north of my
QTH. Those lamps when bad can certainly make an RF racket.
I find my MFJ1025 invaluable at this noisy suburban QTH however. With local
noise that loud as this example it's a no brainer but often noise is bad
enough to ruin receiving conditions but not strong enough to allow effective
nulling on the MFJ - on 160. I have not put in the mods shown on 8JI's site.
But
to remedy that I use a light preamp on the noise antennas (I have several)
using an MFJ959C tuner/preamp which has a small L network tuner in front of a
20db adjustable preamp. Being able to tune the noise antennas and amplify them
slightly greatly increases the abilty to null those noises. Moreover, the
little MFJ preamp is quite flexible having 2 receiver ports and 2 antenna
ports
with full switching between each 4 ports whcih provides great flexibility.
And I have found this preamp to outperform the ICE with out of band crud -
prob because of the tuned front end. The MFJ1026 has a built-in preamp but
I
believe it is hard wired to the internal (useless) whip antenna but could be
rerouted. I don't know if that preamp as an actual gain control tho or just
an attenuator to control output.
I have found several people who claim these nullers never work but that is
opposite my experience. One needs patience and key observation skills to find
the sweet spots in nulling AND they have to know noise can only be nulled from
one source but like this example shows the S/N improvement when hitting one
bad noise source can be dramatic even when other noises are present. The
problem is the operator has to know how to listen and recognize noise sources.
Another of the unique skills in the requisite set for Topbanding..!
73 Pete W2PM
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