On 12/18/2013 3:35 PM, David Gilbert wrote:
A couple of years ago I proposed that Elecraft modify the firmware in
the K3 to allow the phase of the local oscillator in either the main
receiver or the subreceiver to be adjusted in some way (possibly by
using a couple of front panel buttons to be used as
increment/decrement controls). That would allow anyone with both
receivers to put the K3 into diversity mode and sum the signals from
two different antennas in order to null directional interference
(noise or QRM). It would also allow anyone with separately fed
stacked antennas to play around with arrival angles. The absolute
phase angles would be indeterminate and the absolute phase would vary
for every frequency, but nulling at every frequency would still be
possible. The nulling could even be done at the audio output since
relative phase is preserved in the frequency conversion process, but I
assume that it would be more practical to do it where the the majority
of the DSP is already being handled ... i.e., at IF.
At the time somebody at Elecraft agreed it should theoretically
possible and might be worth pursuing, but nothing ever came of it. In
any case, I've always felt that it was a nice opportunity being
squandered. I think it would be a nice plus for the K3 to be able to
do it's own spatial discrimination.
73,
Dave AB7E
Hi Dave and all,
I agree the above should be achievable I have seen such a
scheme implemented wr to professional OTHR systems in both Tx & Rx.
It should not be too hard on the K3 Rx side with 2
identical Rx paths & phase coherence in bothe local oscillators.
I believe it is technically well worth pursueing.
Eric VK3AX.
On 12/17/2013 5:58 PM, Gary Smith wrote:
I've been having terrible RFI issues on the low bands, sometimes its
up to 10M but usually its from 40M & down with 160M being the most
affected. I've become aware of the MFJ and DXEngineering phasing &
noise cancelling systems and how well they work to null out
interference. I'm leaning toward the DXEngineering NCC-1 although the
price is very high and that is holding me back from buying one right
now.
I have Amtrak 100' from my Inv-L transmit and HI-Z Triangular
antennas and Amtrak's 25KV arcing is killing me on the low bands. I'm
wondering if anyone here has a steerable antenna system similar to
the HI-Z that they use for Rx with their sub receiver and... one of
the MFJ or DXE phasing/noise cancelling systems.
If so, how do you have your K3 set up to handle the different systems
and how do you connect your noise cancelling unit so as to still
steer your Rx antenna?
Thanks
Gary
KA1J
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