There have been several questions regarding the effectiveness of
noise canceling devices lately, so I thought I would offer an
anecdotal observation.
I have an MFJ-1026 which I rarely use. I have it connected as
suggested in ON4UN's Low Band DXing, third Ed. That is, the
Beverage(s) connected to the Main Antenna input, transceiver's RX
ANT OUT connected to the Aux Antenna input, and the MFJ-1026 output
to the rig's RX ANT IN. I find this to be a good arrangement with
one problem: using the TX antenna as a noise sense antenna
effectively destroys the directional characteristics of a Beverage
or other directional RX antenna when the noise canceller is in use.
That is why I don't use it for "minor" nose problems. It would be
more desirable to use antennas with similar directional pattern for
both the Main and Aux antennas, I believe.
Something happened with a power line during Friday's snow event. My
normally quiet Beverages all suddenly had noise levels ranging from
a low of S9 (NE) to a high of S9+40 (SW). The NB is not able to do
anything with this particular problem. I have seen this before. It
usually goes away as soon as the temperature rises enough to melt
snow off trees, etc. That doesn't seem to be happening this time.
By careful adjustment of the MFJ-1026 I am able to null the noise
down to S2 NE, S4 W, S7 SW and S1 on a WNW BOG. I cannot find a
useful null when using Beverages in other directions. I changed my
plans for the Stew accordingly. Instead of making a real contest
effort I decided to just see what I could work and have some fun.
Bottom line - in about 8 hours of operating I made 333 Q's, most of
which would not have been possible without the noise canceling
device. I did have fun and got some much needed CW sending practice
(!!) and some copy-under-adverse-conditions practice whether I
needed it or not!
My apologies to those I couldn't hear. Even with a fairly deep null
I still had plenty of noise. Noise is usually S0 (S zero) on all
Beverages. I intentionally manage gain/attenuation to keep it that
way for optimum S/N ratio. After a few hours doing S & P I was
running out of stations to work and decided I was hearing well
enough to risk calling CQ. I picked a poor run frequency at first.
Not only did I have power line noise, but I also suffered strong IMD
products (I was forewarned NOT to buy the rig I did for that very
reason, but let's not get into that now). I was very slow to copy
calls. Even with the pattern disruption due to using an
omni-directional antenna for noise sensing I could still often get
better copy using an appropriate Beverage. The problem being I had
to adjust two controls on the MFJ-1026 to get a null every time I
switched directions. That is not conducive to having a good contest run!
An experimental WNW BOG - 700 feet of 18 AWG insualted stranded
copper wire laying on the ground (now under 30 inches of snow) -
proved useful as it was the best RX antenna for most of NA under
these tough noise conditions. Occasionally it has been the best
antenna for JA, KL7. UA0 zone 19 without noise the noise issue,
beating out my 600 foot NW and W Beverages in S/N ratio. The BOG is
not terminated, but is very uni-directional. Forget about hearing
anything from the ESE on it!
The noise is still there. If anything it seems worse since sunrise
this morning. I'm off to scout the suspect area and see if I can
spot anything obvious, such as a tree laying on a power line! I'm
hoping it is something like that. Otherwise I'm in big trouble. My
last battle with the local utility over noise issues lasted several
years and resulted in only a partial fix.
73,
Paul N1BUG
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