[Elecraft] Anyone use a noise canceller?

[Ron D'Eau Claire]

A different approach that is often very effective is to use a separate
on-ground antenna for receiving! QRN is greatly attenuated at ground level,
much more than signals arriving from overhead. So, while the overall signal
levels are much lower at ground level, the signal to noise ratio is greatly
improved! 

Such antennas are terrible radiators, so you need a rig that can provide an
independent antenna input for receiving. The K3 and K3 provide for separate
receiving antennas. 

On-ground antennas typically show 15 to 20 db lower signal levels than
in-air antennas. That's over 3 S-units, but it's easily made up for by the
low-noise preamplifiers in the Elecraft rigs. 

One common form for such an on-ground antenna is to use some 50-ohm coaxial
line. Put it on the ground (or bury it, but if you do that it's smart to put
it inside a plastic pipe to keep rocks in the soil from pushing on the coax
until they break through the jacket). The coax can be any length but, as you
might guess, longer is better. (Extreme lengths of several wavelengths laid
out in a straight line will show directivity, just like a long-wire in the
air). You can either short the far end of the coax or you can terminate the
far end with a 50-ohm resistor.  If you short the far end you need to make
sure the coax is *not* electrically a 1/2 wave (or multiple thereof) long.
That's because a half-wave line repeats the impedance at the far end at the
rig. If you have far end of an electrically half-wave line is shorted,
you'll see a "short" at the rig! That's not a concern with a 50-ohm
termination at the far end. Doug DeMaw, W1FB (SK) made a cheaper version
from two-conductor "speaker" wire that he said worked very well. Probably
any weatherproof "zip" cord would work. He found a terminating resistor of
about 210 Ohms worked nicely and he used a balun at the rig end to remove
common-mode signals flowing along the two conductors. A length of coax
connected the balun to his rig.

Ron AC7AC