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<p class=MsoNormal><span lang=EN-US>I myself am not yet so far on the digital
radio path that I can do more than dream and visualize. I will already be happy
when I have my complete HPSDR transceiver so that my trustworthy FT990 will
become decoration gathering dust. Give me a year or two (four.. six?). <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Yet I’d would encourage work in the
HPSDR group on:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoListParagraph style='margin-left:18.0pt;text-indent:-18.0pt;
mso-list:l0 level1 lfo1'><![if !supportLists]><b><span lang=EN-US><span
style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New Roman"'>
</span></span></span></b><![endif]><b><span lang=EN-US>Two (or more)
hardware receivers on a single HPSDR<o:p></o:p></span></b></p>
<p class=MsoNormal style='margin-left:18.0pt'><span lang=EN-US>I would like to
install a second and/or third Mercury receiver on the same Atlas.
Don’t know if there is any software supporting such an HPSDR
configuration already?? So really two simultaneous antenna inputs on the
HPSDR, so that we can do spatial filtering. <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:18.0pt'><span lang=EN-US>PAoSIM has
already built a very effective application for two spatial filtering, much
better than the thing FlexRadio demonstrates. He first splits up a 3 kHz passband
in small FFT (IQ) bins, than PER BIN compares phase between both antennas and shows
the results statistically. He than introduces a filter window on the phase
difference. His filter than puts all the FFT samples that don’t pass the
selection to zero, and reconstructs the 3 kHz channel from the remaining IQ
bins. PAoSIM has demonstrated to PA3DES and me that in that way he can very
effectively reconstruct weak signals from one particular direction from a load
of strong interfering signals from several other directions. Not just some
gain, really deleting all the interference!<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:18.0pt'><span lang=EN-US>PAoSIM used two
identical loop antennas, through two synchronized FT1000MP’s, to high-end
audio cards. But you can imagine you can use this system for brick wall
elevation angle selectivity on a stack of two 14 MHz Yagi’s pointing at
Europe, effectively killing all east Coast interference and only hearing clean
DX signals. Any takers?<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:18.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoListParagraph style='margin-left:18.0pt;text-indent:-18.0pt;
mso-list:l0 level1 lfo1'><![if !supportLists]><b><span lang=EN-US><span
style='mso-list:Ignore'>2)<span style='font:7.0pt "Times New Roman"'>
</span></span></span></b><![endif]><b><span lang=EN-US>Very high dynamic range
receiver<o:p></o:p></span></b></p>
<p class=MsoNormal style='margin-left:18.0pt'><span lang=EN-US>Although our
16-bit A/D is probably the best on the market, and the Mercury is holding up
fine, I would still like to have some 10 or 20 dB more dynamic range (IFDR).
There are no RF high-realtime-bandwidth A/D-convertors better than the one we
use yet. But would it be possible to use two in parallel, one with the
preamplifier and one with preamp off (or attenuation on), and to process the
simultaneous output of the two to get one high dynamic range A/D? <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:18.0pt'><span lang=EN-US>That way the
highest bit values would come from the A/D without preamp and have no
distortion from the high level of the combined shortwave, while at the same
time the lowest bit values would come from the other A/D with preamp, giving us
the fine granularity needed for detecting signals deep in the noise.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Kindest regards,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Ben, PA5BW <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>pa5bw@xs4all.nl<o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
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