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<DIV>What I would really like to see is a scheme similar to the openHPSDR
hardware. IIRC, it uses a 122.88MHz VCXO oscillator that can be locked to
an external reference, via a PLL in the FPGA. That external reference is
either an onboard 10MHz oscillator, or a 10MHz signal from a GPSDO, rubidium
standard, or whatever. I have a few of each here, so I can take my
pick. I need to go back and check exactly how the 122.88MHz oscillator is
locked in the Verilog code.</DIV>
<DIV> </DIV>
<DIV>I would prefer to actually replace the 125MHz oscillator with a 122.88MHz
one. I know that messes up using the RP for a lab instrument, but I’m not
sure that is the best use of the RP anyway. Especially without all the
voltage dividers and other front-end junk required to make it a true lab-grade
instrument.</DIV>
<DIV> </DIV>
<DIV>I’m a little concerned about actually running a 120+Mhz signal through the
expansion connector, and the traces on both boards. I’ve had experience
with trying to run 76.8MHz through similar connectors on the Charleston SDR,
without much success. If we actually replace the oscillator on the RP
board itself, then we only need to worry about getting access to the controlling
voltage.</DIV>
<DIV> </DIV>
<DIV>I’m glad to see that both the ADC and DAC clocks are derived from the same
resistor settings.</DIV>
<DIV> </DIV>
<DIV>It still would be nice to see a full schematic of the RP front end.
With that, we might be able to do away with the input lowpass filter components,
and do some subsampling as well.</DIV>
<DIV> </DIV>
<DIV>I wish my funds were less limited, as I would immediately get a second RP
to do some creative dissecting on!</DIV>
<DIV>73, Terry, N4TLF</DIV>
<DIV> </DIV>
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<DIV style="font-color: black"><B>From:</B> <A title=dcmk1mr2@gmail.com
href="mailto:dcmk1mr2@gmail.com">Martin</A> </DIV>
<DIV><B>Sent:</B> Wednesday, November 11, 2015 10:21 PM</DIV>
<DIV><B>To:</B> <A title=jeff@scaparra.com href="mailto:jeff@scaparra.com">Jeff
Scaparra</A> </DIV>
<DIV><B>Cc:</B> <A title=n4tlf@wb4jfi.com href="mailto:n4tlf@wb4jfi.com">Terry
N4TLF</A> ; <A title=tacos@amrad.org href="mailto:tacos@amrad.org">Tacos</A>
</DIV>
<DIV><B>Subject:</B> Re: Red Pitaya SDR update</DIV></DIV></DIV>
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<DIV dir=ltr>There's more discussion on the clock starting here: <A
href="http://forum.redpitaya.com/viewtopic.php?f=11&t=265&start=60#p3062">http://forum.redpitaya.com/viewtopic.php?f=11&t=265&start=60#p3062</A>
<DIV> </DIV>
<DIV>I hope we can find an off the shelf metal case that we can stuff everything
into. I'm using their plastic case with a little 5V fan on the Zynq
module. The whine is driving me crazy.</DIV></DIV>
<DIV class=gmail_extra>
<DIV> </DIV>
<DIV class=gmail_quote>On Wed, Nov 11, 2015 at 5:30 PM, Jeff Scaparra <SPAN
dir=ltr><<A href="mailto:jeff@scaparra.com"
target=_blank>jeff@scaparra.com</A>></SPAN> wrote:<BR>
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<DIV dir=ltr>Looks like we can utilize an external clock but it wouldn't be
10MHz.
<DIV> </DIV>
<DIV><A href="http://wiki.redpitaya.com/index.php?title=External_ADC_clock"
target=_blank>http://wiki.redpitaya.com/index.php?title=External_ADC_clock</A><BR></DIV>
<DIV><A href="http://forum.redpitaya.com/viewtopic.php?f=9&t=17"
target=_blank>http://forum.redpitaya.com/viewtopic.php?f=9&t=17</A><BR></DIV></DIV>
<DIV class=HOEnZb>
<DIV class=h5>
<DIV class=gmail_extra>
<DIV> </DIV>
<DIV class=gmail_quote>On Wed, Nov 11, 2015 at 7:20 PM, Jeff Scaparra <SPAN
dir=ltr><<A href="mailto:jeff@scaparra.com"
target=_blank>jeff@scaparra.com</A>></SPAN> wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV dir=ltr>Has anyone evaluated the clock on the RP or used it for JT65?
Is it good enough? Is there a way to provide a 10MHz reference that is
common on some other radios? I always wanted a good reason to build a
rubidium clock source. :) I do believe the Red Pitaya will be a better
radio. 14 bit ADCs and Direct Sampling should be able to have better dynamic
range and less noise. Some shielding will be needed for the Red Pitaya as I
get much better results with a metal cover over it (probably just picking up
noise in my "shack"). </DIV>
<DIV>
<DIV>
<DIV class=gmail_extra>
<DIV> </DIV>
<DIV class=gmail_quote>On Wed, Nov 11, 2015 at 2:50 PM, Terry N4TLF <SPAN
dir=ltr><<A href="mailto:n4tlf@wb4jfi.com"
target=_blank>n4tlf@wb4jfi.com</A>></SPAN> wrote:<BR>
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<DIV>I am definitely interested Martin. After I straighten out a few
things, I can do both the LF and RP. Right now, I have so many
different versions of PowerSDR and Quisk on so many computers, it’s hard
to keep track!</DIV>
<DIV> </DIV>
<DIV>I am glad that you are taking charge of this! The Red Pitaya is
definitely a wonderful SDR platform. I wish the HPSDR guys would get
more interested in it, as I think the RP platform would be better than the
present Hermes Lite. Of course, the RP costs a little more, but look
at what the hardware can do!</DIV>
<DIV>73, Terry, N4TLF</DIV>
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<DIV style="BACKGROUND: #f5f5f5">
<DIV><B>From:</B> <A title=dcmk1mr2@gmail.com
href="mailto:dcmk1mr2@gmail.com" target=_blank>Martin</A> </DIV>
<DIV><B>Sent:</B> Wednesday, November 11, 2015 1:35 PM</DIV>
<DIV><B>To:</B> <A title=tacos@amrad.org href="mailto:tacos@amrad.org"
target=_blank>Tacos</A> </DIV>
<DIV><B>Subject:</B> Red Pitaya SDR update</DIV></DIV></DIV>
<DIV> </DIV></DIV>
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<DIV>
<DIV dir=ltr>Thanks to Pavel Demin, the Red Pitaya now has a couple of SD
card images to support a wide array of interesting and useful
software.
<DIV> </DIV>
<DIV>There's a <A
href="http://pavel-demin.github.io/red-pitaya-notes/sdr-transceiver-hpsdr/"
target=_blank>dual receiver single transmitter</A> configuration that acts
like a HPSDR network interface with dual receivers and a
transmitter. This opens up the possibility of using PowerSDR, Quisk,
an Android app or other software. It seems like diversity reception
works in PowerSDR.</DIV>
<DIV> </DIV>
<DIV>
<DIV>I'd like help design and build the rest of the stuff it takes to turn
the RP into a robust, portable transceiver. I've never done this
before and hope there's others on this list who would be interested in
joining me. We have some great resources in the club although I know
everyone is time constrained. I'm willing to commit significant time
and effort to the project.</DIV>
<DIV> </DIV>
<DIV>
<DIV>I realize there's time sensitive work going on in the AMRAD Low
Frequency world. That said, I'd like to propose this as a AMRAD project to
follow on the Charleston receiver as time permits. As most of the
digital heavy lifting has been done it's mostly a matter of building the
analog transmit/receive chain and ancillary stuff. </DIV>
<DIV> </DIV>
<DIV>Terry N4TLF has done testing on the RP LF performance and found it
too noisy to be useful but perhaps there's a fix. </DIV>
<DIV> </DIV>
<DIV>The <A href="http://store.redpitaya.com/red-pitaya-board.html"
target=_blank>Red Pitaya</A> is now $238 so an affordable, complete HF SDR
transceiver should be possible. <BR></DIV>
<DIV> </DIV>
<DIV>This could be a great project for the club that hopefully attracts
interest and new members. </DIV>
<DIV> </DIV>
<DIV>So - anyone else in? What do you think?</DIV>
<DIV> </DIV>
<DIV>73 Martin W6MRR.<BR></DIV>
<DIV> </DIV>
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<HR>
<SPAN>_______________________________________________<BR>Tacos mailing
list<BR><A href="mailto:Tacos@amrad.org"
target=_blank>Tacos@amrad.org</A><BR><A
href="https://lists.amrad.org/mailman/listinfo/tacos"
target=_blank>https://lists.amrad.org/mailman/listinfo/tacos</A><BR></SPAN></DIV></DIV></DIV></DIV><BR>_______________________________________________<BR>Tacos
mailing list<BR><A href="mailto:Tacos@amrad.org"
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