Topband: Noise Cancellation Options?

[Markus Hansen]

Hi Walt:

I own a ANC-4 and  a MFJ-1026 that I use with my own version of a rotatable
Diamond shaped terminated loop low noise receiving antenna.  I have never
been able to consistently achieve a deep null with the MFJ-1026 where as the
ANC-4 is very effective.  I know that W8JI indicates that according to his
observations and tests that the MFJ-1026 is more effective than the ANC-4?

I tried several noise antenna's before I found one that worked for me.  What
works for me for the noise antenna is a 40 meter dipole located in the attic
of our home at the opposite end of the house to the Diamond terminated loop,
a distance of 80 feet.  I found that if the noise antenna and the Diamond
terminated loop are located any closer I can not achieve a deep null.  Being
able to rotate the Diamond loop while adjusting the noise canceller is a big
advantage.

The other big issue is the transmitting antenna has a very large capture
area and of course the small Diamond terminated loop has very small capture
area.  If the transmitting antenna and the low noise listening antenna are
close to each other then the circulating RF current in the transmitting
antenna (which captures a lot of noise) over powers the small Diamond loop
and literally transmits its noise to the small Diamond loop by mutual
coupling.  BIG PROBLEM.

The other issue that must be addressed is common mode pickup on the coax
feed line of the low noise receiving antenna.  No use having a low noise
listening antenna like the Flag, EWE or K9AY array if noise is being picked
up on the shield of the coax feed line and being transmitted to your
receiver.

I have addressed all these issues with details of my small Diamond
Terminated loop on my WEB site at
http://www.shelbrook.com/~ve7ca/Ant160.htm

Hope this is helpful.   Markus  VE7CA

PS.  I am investigating further why I can't achieve a good null with the
MFJ1026 and when I find why, I will post it info here.


On Thu, Oct 1, 2009 at 12:16 AM, Walter Miller, AJ6T <aj6t at comcast.net>wrote:

> 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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-- 
Markus Hansen
VE7CA,   North Vancouver, BC  CANADA
Web site:  http://www.shelbrook.com/~ve7ca/