One reason the Elecraft IF DSP (or any other IF DSP) works is that it's
applied before the AGC detector, keeping the noise from reducing
receiver gain. Quite a few audio DSP boxes are available, though and one
might work well, depending on the type of noise. The disadvantage to
conventional audio DSP is that noise that drives the AGC reduces
receiver gain.
You might consider an analog RF noise cancelling accessory; ask around
locally and see if anyone has one you could try.
Below are links to some eham reviews. You can be sure of hearing
everything bad about a product at that site as well as the good, and
some of it will be worthwhile heads-up's. Some reviews, however, will
also mention how to avoid what the bad reviews don't like, usually but
not always RTFM.
MFJ-1026 and 1025 http://www.eham.net/reviews/detail/1205
http://www.eham.net/reviews/review/105339 (the 1025 model has no preamp)
DX Solutions NCC-1
http://www.eham.net/reviews/detail/7361
Timewave ANC-4 (formerly sold as the JPS ANC-4)
http://www.eham.net/reviews/detail/1138
Odds are that your noise is radiated from the building wiring and you
may find success by coupling the "noise antenna" input on any of these
to that wiring with a current probe made from a split RFI ferrite; see
http://www.interferencetechnology.com/the-hf-current-probe-theory-and-application/
If you coupled to a power wire near the antenna that might work, but you
run the risk of also cancelling any of thw desired signal the wiring
picks up, and also overloading or damaging the noise canceller with the
high RF level when you (or any other rooftop antenna user) transmit.
A disadvantage to RF noise cancelling is that -- assuming it works in
your situation - it will probably need to be readjusted for each
frequency your net uses. That might be easier once you mark the control
positions where a null is found. And because it is in line with the
transmitted RF when you key up, you may want to key the cancellers'
RX/TX relay with a PTT signal instead of using built-in RF sampling.
Keeping the noise-sampling antenna/probe away from the transmitter
antenna is a good idea because of that problem, too, and the fact that
if outside, it can pick up the desired signal as well and reduce THAT.
Cortland
KA5S
http://www.interferencetechnology.com/the-hf-current-probe-theory-and-application/#sthash.MQFkIEKB.dpuf
On 2/21/2014 8:30 PM, wa3afs@nycap.rr.com wrote:
We did try a KX3 and its DSP was quite an improvement. That is why I am
looking to see
what rigs may work well in this environment and the budget of the NWS who have
agreed to
'look into' andd possibly fund this effort.
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|