Example red pitaya .c2 files for ft8?

Steve Haynal

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Oct 24, 2020, 8:20:53 PM10/24/20

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Hi Group,

I'm trying to get the hermes-lite to work with the ft8d .c2 4000Hz decoder used on the red-pitaya. I've recompiled it for x86. I've updated the hermes-lite to generate 4000Hz complex data. I can't get ft8d to decode my data. I'd like to check if there is a problem with my .c2 files. Are there any red-pitaya users on this list who could send me one or two known good .c2 files?

73,

Steve
kf7o

Steve Haynal

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Oct 24, 2020, 10:12:34 PM10/24/20

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Hi Group,

I figured out that Q in the IQ stream needs to be inverted. I see good decodes now with ft8d.

73,

Steve

kf7o

PA3GSB

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Oct 31, 2020, 3:42:03 PM10/31/20

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Hi Steve,

Iam also not seeing decodes.... what do you mean with inverting the Q in the IQ stream?

73 Johan

PA3GSB

Op zondag 25 oktober 2020 om 03:12:34 UTC+1 schreef softerh...@gmail.com:

ron.ni...@gmail.com

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Oct 31, 2020, 4:00:19 PM10/31/20

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Same issue. I low-pass filtered and downsampled some IQ files (that decode with jt9 on my Raspberry Pi 4) to 4k sample rate complex floats. Pavel's ft8d reads them, but then quits without printing out anything. Also tried it with Q negated, same result. I may need a working sample file to compare what I did (wrong) with something that works.

73,

Ron

n6ywu

Steve Haynal

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Oct 31, 2020, 5:49:25 PM10/31/20

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Hi Johan and Ron,

Sorry for the imprecise language. I needed to use the complex conjugate of the complex IQ stream coming from the HL2. The attached Python receiver expects 4000kHz data from the HL2 and you can see the negation of Q at lines 117 and 119. Also, the dial frequency must be offset towards the center of the FT8 bands. See below for the proper frequencies to use:

https://github.com/pavel-demin/red-pitaya-notes/blob/master/projects/sdr_transceiver_ft8/app/write-c2-files.cfg

Pavel pointed me to some example files:

https://github.com/pavel-demin/red-pitaya-notes/issues/985#issuecomment-716115841

73,

Steve

kf7o

rx4000a.py

PA3GSB

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Nov 1, 2020, 5:06:39 AM11/1/20

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Steve,

Tnx.

Still not gettting it to work... iam using the receiver_nco as attached.

How does your cic setup looks like?

73 Johan

PA3GSB

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Nov 1, 2020, 5:08:56 AM11/1/20

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attachment seems to be missing...

cic-4k.zip

PA3GSB

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Nov 1, 2020, 5:45:28 AM11/1/20

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Steve,

Working.

I had to shift the command with 1 bit.

73 Johan

PA3GSB

Op zondag 1 november 2020 om 11:08:56 UTC+1 schreef PA3GSB:

attachment seems to be missing...

PA3GSB

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Nov 1, 2020, 12:10:53 PM11/1/20

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Maybe also nice to see:

connecting to gnuradio using the zmq library ; making a spectrum picture using the 4K cic filters... only a small drooping at the edges.

Still some work ahead to before sharing!

73 Johan

PA3GSB

Op zondag 1 november 2020 om 11:45:28 UTC+1 schreef PA3GSB:

Steve Haynal

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Nov 1, 2020, 5:15:29 PM11/1/20

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Hi Johan,

I added Hermes-Lite2/gateware/rtl/radio_openhpsdr1/receiver_4000.v and variant Hermes-Lite2/gateware/variants/hl2b5up_4000 to github for your reference. I still use the final FIR filters so there are 5 receivers max. I haven't fine tuned the overall gain and I suspect the output levels are a bit low. There is only one fixed rate of 4000Hz supported.

73,

Steve

kf7o

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