[TangerineSDR] Setting up DE for selected bands and sample rate

John Gibbons jcg66 at case.edu
Sat Apr 18 18:03:15 EDT 2020

Getting the estimator is easy - you know what it's supposed to be.
In our case we're 1 KHz off the beacon frequency, so it will ALWAYS be

John N8OBJ

John C. Gibbons
Director - Sears Undergraduate Design Laboratory
Dept. of Electrical Engineering and Computer Science
Case Western Reserve University
10900 Euclid Ave, Glennan 314
Cleveland, Ohio  44106-7071
Phone (216) 368-2816 <216-368-2816> FAX (216) 368-6888 <216-368-6888>
E-mail: jcg66 at case.edu

On Sat, Apr 18, 2020 at 3:25 PM Tom McDermott via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> Hi Nathaniel -
> Responding to question 1: the requirements for the DE putting out 8
> channels sampled at 10 Hertz are similar to 8 channels
> sampled at higher rates. The very low sample rate requires the FPGA low
> pass filters have many more taps, but I think
> that's small-ish compared to other FPGA things.
> Responding to #2 (from the original post) The algorithm in the paper would
> probably be implemented in the Local Host as software.
> I'm not sure it would be easy nor useful to figure out how to compute that
> in FPGA as opposed to in CPU.   But at 10 Hz sample rate,
> that computation is likely feasible in CPU. There will be the initial
> collection of samples to get the estimator started, then it can update
> frequently (i.e. 1 second rate).
> I can't comment on question 3.
> -- Tom, N5EG
> On Sat, Apr 18, 2020 at 3:37 AM Dr. Nathaniel A. Frissell Ph.D. <
> nathaniel.frissell at scranton.edu> wrote:
>> Hi Bill and Tom,
>> 1. If we run the DE in the 8 channel mode for doing these measurements,
>> do we think that will max out the data engine to prevent it from doing
>> anything else?
>> 3a. I agree that we probably do not want to emulate a sound card. I would
>> like to see a program like FLDigi be able to accepts files or buffers. It
>> would be good not only for the PSWS, but al also for doing post-processing
>> of data in general.
>> 3b. We need the ability to collect both the raw spectrum and the derived
>> frequency estimate. Exactly how to interpret and use these things is still
>> an active area of research. Steve WA5FRF is actively working on this and is
>> probably the best person to work with on this right now.
>> Maybe David Kazdan can comment to address Tom’s question on needing 100
>> seconds of measurements.
>> 73 de Nathaniel W2NAF
>>>> Dr. Nathaniel A. Frissell, Ph.D., W2NAF
>> HamSCI Lead
>> Assistant Professor
>> Department of Physics and Electrical Engineering
>> University of Scranton
>> (973) 787-4506
>> On Apr 17, 2020, at 1:41 PM, Tom McDermott via TangerineSDR <
>> tangerinesdr at lists.tapr.org> wrote:
>> Hi Bill - thanks for the link to the paper.   I don't have access to the
>> references in the paper, particularly
>> [1], [2], [3], and [4], so I am missing the details of the critical first
>> step.  My reading of the paper indicates that
>> the initial estimate of the frequency is needed, and that initial
>> estimate has to distinguish between adjacent
>> spectral bins, those being +/-fs/N apart. (Section 2.1, step 1.)
>> So perhaps I'm reading this wrong, but it still seems like one needs 1000
>> samples to separate
>> out the desired bin, assuming 10 Hz sample rate and 10 milliHz
>> resolution, that is 100 seconds.
>> [ The DFT doesn't need a power-of-two sample size, it can just be a
>> convenient number. ]
>> -- Tom, N5EG
>> On Fri, Apr 17, 2020 at 8:52 AM Engelke, Bill via TangerineSDR <
>> tangerinesdr at lists.tapr.org> wrote:
>>> In yesterday’s HamSCI research telco
>>> <https://scranton.zoom.us/rec/play/tMd4JO39-j43H4WQ5gSDC_AtW9S_ffmsgHcd-KJZy0uzUiIAZlPwMuQSYbeIYiPAWTSPSeb1nkzcpCCR?startTime=1587063159000&_x_zm_rtaid=NMAJy4E0RWahMdU1UXtvsg.1587138515458.823452708c432bc18700b9c14edfeb54&_x_zm_rhtaid=286>,
>>> we discussed several ideas on how to accomplish several goals with the
>>> TangerineSDR; a summary is below for your review and comment.
>>>    1. We currently think that the Data Engine (DE) will have the
>>>    capacity to simultaneously collect up to 8 channels of data for observing
>>>    Doppler shift in carrier frequencies, i.e., WWV at 2.5, 5, 10, 15, 20 MHz
>>>    plus CHU at 3.33, 7.335 and 14.670 MHz.  We think we can do this by
>>>    observing excursions of up to +/- 1 Hz from the carrier frequency with a *precision
>>>    of 0.01 Hz, with measurements taken every second *(see next point).
>>>    2. In earlier discussions on this board, it has been stated that
>>>    this kind of precision (10 milliHz) would require a 102.4 second sample
>>>    time; this assumes the processing is linear. CWRU is using a non-linear
>>>    method in the low-cost approach to extract a frequency estimate, which uses
>>>    fldigi to achieve the 10 milliHz resolution once per second, and it was
>>>    discussed that TangerineSDR could be set up to do this as well. (Reference
>>>    here:
>>>    http://citeseerx.ist.psu.edu/viewdoc/download?doi=
>>>    )
>>>    3. I won’t try to explain the method mentioned above, as it is at
>>>    the very limits of my understanding; however, a couple of observations…
>>>       1. The CWRU low-cost system uses fldigi to implement the
>>>       frequency estimator, and in looking at fldigi I see that it requires sound
>>>       card input. In the case of the TangerineSDR, we will have buffers of IQ
>>>       data. I don’t think I want to use some sort of kludge to take the buffers
>>>       and somehow emulate a sound card (do I?) – another option might be to
>>>       implement the frequency estimator algorithm in the Small Board Computer
>>>       (SBC) of the TangerineSDR. If we could/should do this, I would ask for a
>>>       volunteer to code it; I fear that if I try to do it, it would take far too
>>>       long for me to get up the learning curve. The code (C++) for the algorithm
>>>       as used in fldigi is online (included with hundreds of other routines; see
>>>       http://www.w1hkj.com/files/fldigi/ ). A third option might be to
>>>       persuade the fldigi team to support buffer or file input.
>>>       2. As I understand, the frequency estimator outputs a single
>>>       value: the strongest signal in the band. A downside of this is that there
>>>       seems to be a lot of other possible information in the data (Steve Cerwin
>>>       has shown data he has collected showing Doppler effects but with multiple
>>>       structures including various modes in both time and frequency domain). We
>>>       need some guidance from the science community: what data do we really need
>>>       to do the desired science?? Maybe we need to implement/support both raw
>>>       data collection & frequency estimation at the same time(?)
>>>       3. In yesterday’s call, we discussed that we should be able to
>>>       specify an 8 ksps sample rate and a center frequency, and get the desired
>>>       10 milliHz resolution – frankly, I am still fuzzy on the details of this,
>>>       so I wish someone (David Kazdan? Kristina?) would chime in and explain, for
>>>       the record, how this works.
>>>    4. Channel configuration settings for the DE:
>>>       1. The DE will be able to tell the SBC what data rates it
>>>       supports. We are working with 2-byte command codes; in general, a command
>>>       ending in “?” is a query, i.e., send the DE the command “S?” and it answers
>>>       “AK” , a simple health check.  Send the DE the command “R?” – it will
>>>       respond with a table such as the following:
>>>               1  2000    2  4000    3  8000    4  16000     etc. – where
>>> each entry is 2 integers: an index and a sample rate (Hz). To put a channel
>>> into data rate of 8000 sps, we put 3 into the channel setting.
>>> Please comment!                   -73- Bill, AB4EJ
>>> --
>>> TangerineSDR mailing list
>>> TangerineSDR at lists.tapr.org
>>> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>> --
>> TangerineSDR mailing list
>> TangerineSDR at lists.tapr.org
>> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20200418/db05a05a/attachment.html>

More information about the TangerineSDR mailing list