Not being familiar with the architecture or sources, would there be any
value in developing a 2-input, LMS-style noise reduction scheme using
the same antenna for both receivers and a small frequency offset? (RX2
would be tuned to an unoccupied "noise" frequency as close as possible
to the "active" RX1 operating frequency)
That technique has been successfully used elsewhere and has the
advantage of adaptively canceling any static or long-term difference in
"phase" between the signals. (primarily group delay in this case?). The
obvious disadvantage is having to choose a suitable noise frequency on a
busy band, assuming one is available.
Thoughts?
Thanks,
Jim Barber, N7CXI
Bob McGwier wrote:
Eric and I have begun adding the diversity reception capability to the
Flex 5000. It will work for those 5000's which have the RX2
installed. In my diversity branch, one can find the enabled code.
It is VERY rough but as you can tell from Lee's blog:
http://w9oy-sdr.blogspot.com/
the software antenna diversity can be used for signal enhancement by
increased gain or by noise source nulling.
It is rough to use and must be done manually for now.
If you start running the code
svn co
svn://206.216.146.154/svn/repos_sdr_windows/PowerSDR/branches/n4hy/diversity/bin/Release
you will be able to type ctrl-alt-D and bring up the form that you can
see on Lee's blog. With RX1 and RX2 hooked to separate antennas, you
"tune the array" using the right hand side of the DSP form.
When you bring it up, and you have set RX1 and RX2 to the same mode
and filter size, you click "sync" and then enable. This does several
things. It locks the two VFO's together in hardware and then enable
does it in software as well.
You then play with mag, angle, and gain to optimize the signal you are
wishing to listen to. This is pretty rough, but it does work. This
will be automated for HF Shortwave folks in SAM-Diversity as soon as
possible to do automated signal combining and as we learn from that,
we will add additional capabilities. After this is completely vetted
and made easier to use, it will be added to the main stream.
THANK YOU to Lee for doing this blog entry and adding the mp3's
showing the effects.
Bob
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