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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Brain dump coming…<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I want to collect the various ideas for the <st1:place
w:st="on">Gibraltar</st1:place> board so I can get clearly in my mind what is
being proposed. I come up with roughly three sets of things.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><span
style='mso-list:Ignore'>1)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Producing a high-quality
frequency reference.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><span
style='mso-list:Ignore'>2)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Using a
high-quality frequency reference.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><span
style='mso-list:Ignore'>3)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Producing a
high quality absolute time reference.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>[I’m imagining two possible platforms, one as a single
card in an Atlas-based SDR and the other is the same card in a separate
Atlas-based box as a test instrument. The latter could have additional
distribution cards in it, and maybe a low-cost USB interface card.]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Case 3) would be useful for coherent CW and the like where
the two contact ends are not synchronized by the signal but by absolute clocks.
Cf. long baseline interferometry. Presumably, the frequencies need to be
accurately locked as well. I assume that this takes a GPS module with a 1 PPS
output and a decoding of the NMEA time message or equivalent for the clock part.
A distribution card like the TADD-3 might also be useful in an Atlas format. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Case 2) would be using a reference to lock a VCXO with a PLL
to make a LO [don’t ya’ love these abbreviations?] for a VHF/UHF
XCVR. Or to clean up a DDS for a VFO. Or to measure the frequency of the
SDR-1000’s reference oscillator and provide a correction value so the
software could accommodate the drift.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Case 1) seems to cover the widest range of possibilities. You
might have an external reference source like a cesium or rhubidium source that you
want to discipline against the GPS signal. This, as I understand it, gives
fantastic long-term stability but not so hot phase noise. Or one could take an
extremely good VXCO, like the Crystek. This gives slightly worse long-term
stability, though a few parts per ten trillion is nothing to sneeze at, but
much better phase performance. Either of these would be good for microwave and
lower frequency locking via 2). Or one could use a less expensive VCXO or make
one’s own, discipline it to the GPS and have something adequate for HF
work.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>What seems to be in common here, and which I presume goes on
<st1:place w:st="on">Gibraltar</st1:place> is<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><span
style='mso-list:Ignore'>1)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>A good GPS module
with 1 PPS output, preferably a timing model that can go into fixed position
mode and use any redundant satellite signals to correct the time, not the
position.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><span
style='mso-list:Ignore'>2)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>A very low
frequency PLL, minutes to hours, for disciplining the reference to the GPSS 1
PPS.<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in;mso-list:l1 level1 lfo2'><![if !supportLists]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><span
style='mso-list:Ignore'>3)<font size=1 face="Times New Roman"><span
style='font:7.0pt "Times New Roman"'> </span></font></span></span></font><![endif]><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>A more
regular frequency PLL to use the reference to lock something else.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>So, footprints for a couple of GPS modules. A fair sized
FPGA/CPLD for the PLL chains. Some conditioning circuitry. Place for a very
good or pretty good VCXO/OCXO [where does the 15V come from?]. I/O for
reference, PLL control outputs, I/O for controlled oscillator, 1 PPS I/O.
Antenna feed with power to same. Does this seem like a reasonable core for <st1:place
w:st="on">Gibraltar</st1:place>? Plus. TADD-1 and TADD-3 style fan-out boards.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> Chris
– AE6VK<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>[Now to see what Steve actually has in mind…]<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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