[TangerineSDR] Frequencies for FT8 & WSPR

[Dave Larsen]

Bill --

another option is Rob Robinetts system with kiwisdr and rpi 3

Here he describes it at DCC 2019

https://www.youtube.com/watch?v=nHVN8oUUtlE

Rob has checked into tangerinesdr net several times and talks at Hamsci

Dave KV0S



On Wed, Nov 25, 2020 at 10:50 AM Engelke, Bill via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> Hello All:
>
>
>
> A week ago in the TangerineSDR telco, we touched on an issue regarding
> frequencies for FT8 and WSPR. I’m interested to know what folks think about
> what should be done here.
>
>
>
> The question is this:  when setting the Data Engine (i.e., the radio part)
> to a frequency for FT8 or WSPR reception, we have used the term “center
> frequency,” thus suggesting we might set the DE to the center of the
> respective sub-band (see table below). Perhaps that is compatible with IQ
> sampling, where we recognize the frequency of the signal by the phase
> difference between I and Q; so signals below the center would have a
> negative phase shift (“negative frequency”), signals above a positive shift.
>
>
>
> I have a question:
>
>
>
>    - The decoders for both WSPR and FT8 assume the receiver is set to a
>    dial frequency (per the WSPR and FT8 band plans) and receiver is in USB.
>    This produces a baseband signal (that can be collected by a sound card) in
>    the audio range. I am fuzzy on the correct way to convert this signal – do
>    we set the DE’s frequency to the dial frequency and assume that the decoder
>    will ignore everything in the negative frequency area, or do we set the
>    DE’s frequency to the center of the sub-band?
>    - Just as a note, Scotty and Martin, who are planning to do the FPGA
>    programming, voiced some concerns about whether the DE could actually be
>    set to the required frequency (be it “dial frequency” or “center of the
>    sub-band”), due to open questions about the clock’s output (?) – I am fuzzy
>    about the details here, but as recall, the way we left it was that Scotty &
>    Martin are going to have a look at the Pavel Demin FPGA code to see how he
>    accomplished it (which may answer the question above). What I do know is
>    that the Raspberry Pi does not have the capacity to accept a wide-band data
>    feed( (i.e., encompassing all FT8 & WSPR frequencies) and doing the
>    filtering to slice out the sub-bands for the decoder; that would take a
>    high-end desktop.
>
>
>
> If anyone has any thoughts, please post. Below is the table of frequencies:
>
>
>
> *Frequencies for FT8*
>
>
>
> (4000 samples/sec)
>
>
>
>
>
> Dial Freq. in MHz
>
> in Hz
>
> lowest signal
>
> center
>
> top of band
>
> 1.84
>
> 1840000
>
> 1840200
>
> 1841500
>
> 1843000
>
> 3.573
>
> 3573000
>
> 3573200
>
> 3574500
>
> 3576000
>
> 7.074
>
> 7074000
>
> 7074200
>
> 7075500
>
> 7077000
>
> 10.136
>
> 10136000
>
> 10136200
>
> 10137500
>
> 10139000
>
> 10.074
>
> 10074000
>
> 10074200
>
> 10075500
>
> 10077000
>
> 18.1
>
> 18100000
>
> 18100200
>
> 18101500
>
> 18103000
>
> 21.074
>
> 21074000
>
> 21074200
>
> 21075500
>
> 21077000
>
> 24.915
>
> 24915000
>
> 24915200
>
> 24916500
>
> 24918000
>
> 28.074
>
> 28074000
>
> 28074200
>
> 28075500
>
> 28077000
>
> 50.313
>
> 50313000
>
> 50313200
>
> 50314500
>
> 50316000
>
> 50.323
>
> 50323000
>
> 50323200
>
> 50324500
>
> 50326000
>
>
>
>
>
>
>
>
>
>
>
> *Frequencies for WSPR*
>
>
>
> (375 samples/sec)
>
>
>
>
>
> Dial Freq. in MHz
>
> in Hz
>
>
>
> center
>
>
>
> 0.136
>
> 136000
>
>
>
> 137500
>
>
>
> 0.474
>
> 474000
>
>
>
> 475500
>
>
>
> 1.8366
>
> 1836600
>
>
>
> 1838100
>
>
>
> 3.5686
>
> 3568600
>
>
>
> 3570100
>
>
>
> 7.0386
>
> 7038600
>
>
>
> 7040100
>
>
>
> 10.1387
>
> 10138700
>
>
>
> 10140200
>
>
>
> 14.0956
>
> 14095600
>
>
>
> 14097100
>
>
>
> 18.1046
>
> 18104600
>
>
>
> 18106100
>
>
>
> 21.0946
>
> 21094600
>
>
>
> 21096100
>
>
>
> 24.9246
>
> 24924600
>
>
>
> 24926100
>
>
>
> 28.1246
>
> 28124600
>
>
>
> 28126100
>
>
>
> 50.239
>
> 50239000
>
>
>
> 50240500
>
>
>
>
>
>
>
> -73- Bill , AB4EJ
> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>


-- 
KV0S - Dave Larsen
Columbia, MO, USA
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