[Elecraft] Plasma TV Noise any ideas on how to filter it out.

[Jim Wiley]

KL7DTH and myself share a station.  We have a DX engineering NCC-1 box 
specifically purchased to remove interference from the neighbor's plasma 
TV.   Once we figured out how to  use the unit, it  completely removes 
the trash from the plasma RFI generator.  And we mean completely - zip, 
nada, nothing left.  It does not seem to detract from the intended 
signal at all.   


We use the NCC-1 primarily  on 75 meters, but it also works on 160 and 
40.   We are blessed with what is otherwise a very quiet receiving 
location.  Our noise level on 75 and 40 meters is S-zero, on 160 is is 
about S-1.   We use a full-sized cubical quad on 75 meters, arranged in 
a NVIS (vertical firing) configuration.  We have similar antennas for 
160 and 40, all made of wire and strung among the trees on our 2.5 acre, 
or just a bit more than a hectare for our metric friends.   


Some points:  The :sense" or "noise" antenna needs to be located as 
close as possible to the noise source.  


The sense antenna need not be very high.  In fact you want it to perform 
poorly on the frequency you  are trying to hear.  


The sense antenna need not be resonant.  As long as it gets enough noise 
signal to do the job, stop there. Resist the temptation to make the 
sense antenna perform like an ordinary ham antenna. 


We first tried a noise antenna about 200 feet away from the source, but 
performance was not impressive.  We then erected a non-resonant dipole 
about 15 feet high but right on the property line between us and the 
neighbor.   The results were immediate and impressive.  Adjusting the 
controls of the NCC-1 resulted in complete cancellation of the plasma TV 
hash, and signals that were completely covered by the hash popped out of 
the noise and came in loud and clear. 


Some further points:  First, the usual disclaimers apply - no 
connection, etc.  Next. there are other units that may work equally well 
on this type of noise.  We have only tried the one unit, and it worked, 
so we stopped looking.  It should be quite possible to homebrew one of 
these units.  There is no "rocket science" here.   Parts should be 
easily  available.  I seem to remember that a design for  something like 
this appeared in  one of the RSGB or ARRL handbooks a while back.    The 
NCC-1 is intended, according to DX engineering's literature,  primarily 
for steering phased arrays, with a secondary use for interference  
reduction. 

On Topic note - considering the potential for assisting QRP operations, 
it seems to me that this type of unit would be a good candidate for an 
Elecraft kit.   I know I would like one in a footprint small enough to 
carry around with my K2. 


- Jim, KL7CC


 

David Cutter wrote:
>
> Secondly, the concern about ruining the performance of the rx with noise 
> phase cancelling boxes did not draw attention to the DX Engineering version 
> which, they say, is specifically designed to provide very high TOI. 
>