I have local noise problems which come and go depending on time of
day, day of week etc. I didn't like the idea of having a noise
cancelling device in the high power transmit path, so picked up a DX
Engineering NCC-1 which is perfect for use with my K3, inserted between
the antenna OUT and antenna IN jacks. I have a horizontally polarized loop
which I use as the RX antenna on the K3 when I need to fight noise. A
vertical doublet antenna is used as the transmit antenna, which serves as
the noise sense antenna in receive when the NCC-1 is active.
To do this, the loop antenna goes to antenna port A on the NCC-1
(receive antenna input), K3 antenna OUT (from the transmit antenna)
goes to antenna port B on the NCC-1 (noise antenna input) and the
output of the NCC-1 goes to the K3 antenna IN. K3 KEY OUT goes to NCC-1
T/R CTRL to put it in bypass when the K3 is keyed.
Now I have 3 choices:
1. If I then select the RX antenna on the K3, the NCC-1 is inserted and I
use the quieter loop antenna for receive while nulling noise with the
NCC-1 controls.
2. If I don't select the RX antenna on the K3, the NCC-1 is bypassed, and
the transmit antenna is used for receive.
3. If I select the RX antenna on the K3, but turn the NCC-1 OFF, then I
receive on the loop antenna, but the signal passes straight through the
NCC-1 from antenna port A to the output without modification (sometimes
that's all that's needed, it's much quieter than the vertical when it
comes to the nearby noise pollution sources).
The NCC-1 can provide a very deep null on the receive loop antenna for
vertically polarized noise which is "heard" better on the vertical. The
trick is to correctly balance the levels of the two antenna inputs on the
NCC-1. The balance and phase controls are very precise and repeatable, and
the phase control has a wide range. Having the P3 to look at helps
in identifying the noise and finding what can be a very sharp (but deep)
null.
There are complications. One is that when the NCC-1 is active I need to
disable full QSK on the K3 in CW mode so that the internal bypass relay
in the NCC-1 doesn't make a lot of noise as it follows the keying.
The other involves antenna tuners. I use a KAT500, and if a frequency
change causes it to recall new L and C settings then the NCC-1
phase setting may need to be touched up because the phase of the noise
signal from the transmit antenna is changed (and the NCC-1 null can be
very sharp indeed).
But for me the benefits have far outweighed the costs.
Bob NW8L
On Fri, 2 Jan 2015, Jim Wiley wrote:
We use a NCC1 here also, although with just a low 75 and 40 meter trap
dipole for the noise pickup antenna. It is very successful in
eliminating noise from the neighbor's plasma TV, and other noise sources
that originate in our neighborhood from time to time. It only works on
one noise at a time, of course, but most of the time that is enough.
- Jim, KL7CC
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