SDR Software and hardware

WB4JFI wb4jfi at
Fri Oct 10 16:26:47 CDT 2008

Actually, I am wrong about the low-cost direct-sampling board mentioned
below.  It actually receives 40M, not under-sampling of 2M.  I got
momentarily confused between projects... he had another project that did 2M
operation.  But, it is possible to undersample 2M with a QS-1R
direct-sampling board.  It's also possible to use a QSD at a subharmonic,
for example to use a Brainerd 995x/QSD board at 146MHz/3 to receive 2M.


> -----Original Message-----
> From: at
> [ at]On Behalf Of Terry Fox
> Sent: Friday, October 10, 2008 5:17 PM
> To: Tacos at Amrad.Org
> Subject: FW: SDR Software and hardware
> -----Original Message-----
> From: Terry Fox [mailto:tfox at]
> Sent: Friday, October 10, 2008 3:48 PM
> To: taco at
> Cc: Terry Fox
> Subject: SDR Software and hardware
> Hey guys.  Are we doin' anything as a group?  The election season
> is almost
> over, it's time to be thinking about what to talk about at physical Tacos
> and this forum besides politics, ancient radios, and the latest humorous
> finding on the Internet.  How about new radios?
> I see that the HPSDR group is about to build the Mercury boards for sale.
> This is a 0-65MHz direct-sampling SDR board that plugs into the
> HPSDR Atlas
> bus, and uses Ozy for USB communications to the host computer.
> It is meant
> to be the receiving companion to the Penelope direct-sampling
> exciter board.
> The cost for Mercury will be about $330 or so, through TAPR.  Sort of like
> Phil Covington's QS-1R.  The QS-1R looks very good, btw, but the cost is a
> little steep for me right now.
> My personal opinion is that while the QSD/QSE-based radios (SoftRocks,
> Brainerd, Flex products) are good, the direct-sampling devices will
> represent a true leap in technology.  They virtually eliminate
> the image and
> LO radiation (leakage) of most or all QSD/QSE designs.  Even the
> recent Flex
> radios, which I believe are still QSD/QSE.  Note that even the latest
> versions of PowerSDR does not do receive I/Q balance at multiple points on
> every band.  The same with transmit.  Can you assure that your transmitted
> RF meets the FCC requiements all across the band with only a single IQ
> sample/balance point?  Both the QSD/QSE hardware and the sound
> card response
> contribute to this imbalance issue.
> With 16-bit 130MHz (or higher) RF A/D converters, the hardware can deliver
> at least 14-bits of accurate samples.  Then, processing gain due
> to digital
> down-sampling can provide more bits.  Yes, there are occasions where the
> dynamic range is still not quite good enough, but those conditions are
> getting few and far between.  the IQ balancing is not an issue,
> because this
> process is done via firmware inside the FPGA on digital numbers.  No
> real-world analog components to be out of balance at different
> frequencies.
> Also, Mel and I are playing with SDR software under Linux (and maybe
> Windows).  We are learning to use the QT GUI software, along with a couple
> of IDEs.  QT is supposed to work on both Linux and Windows, so the same
> basic code would be usable on both platforms.  Reality is that
> while QT will
> build the same GUI on both platforms, some of the IO will need to be
> different, due to the different approaches Windows (portaudio) and Linux
> (jack) takes.  We are using the no-cost, open-source version of
> QT, which is
> full-blown but does not include company support.  See
> Eclipse ( is an IDE that can have QT integrated
> into it, and
> is also available for both Linux and Windows.  However, we have found some
> inconsistencies with the most recent combination of QT/Eclipse integration
> platforms.
> While waiting for these inconsistencies to be sorted out, I have started
> playing with QT on Linux, with a couple of other IDEs:  Monkey Studio and
> EDYUK.  Both of these are available at no cost from, under
> the development section.  Both requiring compilation - via QT ironically.
> It is important to note that when using the IDEs mentioned above, they all
> use the same project source code tree, and do NOT require
> additional special
> files.  So, a project can actually be built with any of the three, then
> another used to work on it, depending on the programmer's whim.  All three
> also have full source code.  I have not tried Monkey Studio or EDYUK under
> Windows yet, so I cannot guarantee they are cross-platform.  But, QT and
> Eclipse behave identically on Linux or Windows.
> Someone here in Charleston is also designing a smaller/less expensive
> direct-sampling RF A/D board that plugs into the Digilent Nexys-2
> FPGA demo
> board.  He has it undersampling 2 meter activity and displaying the RF
> spectrum in a window, and is working on demodulating the signals
> now.  This
> is a neat board, not cutting-edge regarding performance (12-bit A/D I
> think), but a great way to learn FPGA SDR software.
> Is anybody else in AMRAD-land interested in working on SDR software?  Care
> to join us?
> Terry
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