[GreenKeys] NYT Feed

[Harold Hallikainen]

Happy new year! Thanks for the comments on the NYT feed (
https://w6iwi.org/rtty/audio/nyt/ ).

I found a typo in setting the number of audio samples per bit for 100 wpm.
That has been corrected, but I'm still not getting great copy out of
fldigi. I connected a logic analyzer to the loop keying output of my DSP
TU and got the attached. The DSP TU also does not print the 100 wpm
correctly, but I suspect there may be an issue in the software uart. I had
not tested it at this speed.

Looking at the attached logic analyzer plot, we see proper decoding of a
string of 0x04 characters (space bar at the beginning of my stream).

Marker X is at the beginning of the first start bit. Marker Y is at the
beginning of D2, so the time from X to Y is 3 bit times (start, D0, D1).
That time is shown as 39.53666 ms. Since this is 3 bit times, 1 bit time
is 13.179 ms. It is ideally 1/75 seconds or 13.333 ms. The plot shows us
running about 1.16% short.

Marker A is at the end of D2. The Y to A time is the duration of D2. It is
13.59649 ms or 1.98% long.

The T (trigger) marker is at the start of the start bit of the first
character. Marker C is at the start bit of the second character. This time
is 100.16313 ms. This is 7.5 bit times (start, 5 data, 1.5 stop), so the
bit time is 100.16313 ms /7.5 = 13.35508 ms or 0.17% long.

These timing errors seem quite small and should allow recovery of the data
(as the logic analyzer did). I have attached the logic analyzer decoded
characters (Baudot) and hand translated a few to ASCII.

It LOOKS like this should work. Does the 100 wpm NYT feed work for others?

THANKS!

Harold
https://w6iwi.org




-- 
Not sent from an iPhone.

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