Topband: MFJ-1026 Noise Cancellation

[W2pm@aol.com]

In a message dated 1/21/2006 8:12:17 AM Eastern Standard Time, tod at 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