Topband: Noise Cancellation Options?

[Tod - ID]

Walt:

One of the best ways to find the noise nulls is to reduce the signal values,
both antenna and sense [aux] inputs, to very low values. Then look for the
nulls. I wrote something about how to do this on my web site  --- but some
time back so I am not sure what I said exactly. However, starting with low
levels one can increase the values after the null is located. Sometimes the
null is near the extremes of the ranges so one needs to do the adjusting
very slowly.

I do not believe that the ANC-4 will be better than the MFJ-1026; in fact,
it may not be as good.

I found that I needed to make sure that the sense antenna was well separated
from the transmit antenna and in some cases I had to add a lot of
pre-amplification on the sense antenna to get the two signals to be equal.
Using the S-meter is not necessarily the best way to compare signal levels.
If you do use the S-meter for comparison, then attenuate the signals so that
you are using only the low values [S1-S3] of the meter. The higher values
are non-linear and significant differences in signal  levels will not show
up very well. As a result it will be difficult to null the noise.

I hope that may help. I found that the MFJ-1026 when properly adjusted
dramatically reduced noise in my environment. [My web site has a couple of
sound bites showing that].  Eventually I was able to find the power line
noise source and the power company quickly eliminated it. That was better
than the MFJ-1026 null !

Tod, KØTO





> -----Original Message-----
> From: topband-bounces at contesting.com 
> [mailto:topband-bounces at contesting.com] On Behalf Of Walter 
> Miller, AJ6T
> Sent: Thursday, October 01, 2009 1:17 AM
> To: Topband at contesting.com
> Subject: Topband: Noise Cancellation Options?
> 
> My new 160m sloping "T" transmit antenna seems to be working 
> well, and now I need to attack the local RX noise problem 
> (again).  A small shielded loop and K9AY help somewhat, but 
> reception is still overwhelmed by noise at my QTH.  I have 
> tried both the MFJ-1025 and MFJ-1026 noise cancellers with an 
> external noise pickup antenna but I have not been able to 
> achieve a null, even with equal S-meter readings from the 
> main and noise antennas.  I am aware that Timewave sells 
> their model ANC-4 with similar specifications (but no hard 
> keying capability).  Are there any other noise cancellation 
> options to consider?  Due to recent construction in the 
> previously-empty field near my shack, Beverages are no longer 
> possible here.  Are some of you using the ANC-4 with success?
> 
> 73, Walt, AJ6T
> 
> 
> 
> 
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