[TangerineSDR] Just joined and some comments

[John Ackermann N8UR]

Hi, Lyle!  Good to see you here!

Here's a PDF of the presentation Tom mentioned.  It's more a survey than 
any deep analysis.

John
----



On 4/26/19 12:42 PM, Tom McDermott via TangerineSDR wrote:
> Hi Lyle,  welcome to the list !
> 
> I started out asking the same questions about 9 months ago.  Evaluation
> of a few units was disappointing for the project needs, especially Red 
> Pitaya.
> 
> John Ackermann N8UR did an evaluation of about 25-30 units, and put together
> a slide deck.  Perhaps we can persuade him to upload it to the mail list.
> 
> One thing we have found so far on virtually all the available SDR units 
> is very
> poor ADC clock stability. Even with externally GPSDO referenced clocks.
> We are trying to time stamp the samples within +/- 50 nanosecond accuracy,
> which a modern GPSDO should be able to achieve.  What we have seen on
> the SDRs looked at is the ADC clock drifting way more than that even 
> when locked to
> a high accuracy oscillator. This is due to several causes, one is the 
> use of phase
> locked loops in deriving ADC clock from reference clock. The FPGA based 
> loops
> so far have worked remarkably poorly.
> 
> We also need to calibrate amplitude, and whilst an easier problem, it's not
> built into the receivers looked at.
> 
> I would still hope it would be possible to use off-the-shelf hardware, 
> but nothing
> suitable has shown up via UPS so far.
> 
> -- Tom, N5EG
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> On Fri, Apr 26, 2019 at 9:07 AM Lyle Johnson via TangerineSDR 
> <tangerinesdr at lists.tapr.org <mailto:tangerinesdr at lists.tapr.org>> wrote:
> 
>     Hello Scotty, Dan and Tom!
> 
>     Still digesting the preliminary document.  I see lots of IO...
> 
>     I also see references to PSWS which seems to be Personal Science Work
>     Station.  Not sure what this is intended to be.
> 
>     I also recall some interest in a "space weather station" but have been
>     out of the loop for too long.
> 
>     The TangerineSDR Data Engine seems to be a general purpose FPGA
>     development board with lots of specialized IO.
> 
>     I am unclear as to what specific problems this project is attempting to
>     solve, or what peripheral board(s) might be needed to solve the problem
>     set that is driving this development.  Are such boards already existing
>     (hence the large set of various standard IO interfaces) or do many/most
>     of them still need to be designed -- and if so how does that play
>     out in
>     the overall scheme of things?
> 
>     TAPR's early history with general purpose solutions not aimed at
>     solving
>     a particular (perceived) need in the community in general meant a
>     lot of
>     development effort by one to five individuals to create something that
>     was only adopted by a few tens (METCON comes to mind).
> 
>     Does a board like the Red Pitaya - especially if it were to have a
>     TAPR-sourced "IO expander" - already solve many or most of the problems
>     that this board attempts to solve?  Or the new Red Pitaya-SDR with
>     bigger FPGA, better ADC, 50-ohm front end, lower noise floor, etc
>     but at
>     $500 (fast 16 bit ADCs and 14-bit DACs) instead of $200 (10-bit fast
>     ADCs/DACs) or $300 (fast 14-bit ADCs/DACs), solve the problem(s)?
> 
>     -Lyle KK7P
> 
> 
>     -- 
>     TangerineSDR mailing list
>     TangerineSDR at lists.tapr.org <mailto:TangerineSDR at lists.tapr.org>
>     http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
> 
> 
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