On 3/14/2018 5:13 PM, Mike Lavelle K6ML wrote:
In WSJT-X, the sound card sample rate is always 48000 Hz and 16 bits,
regardless of the mode (JT4, JT9, ISCAT, JT65, FT8, etc) selected?
Correct.
The protocol descriptions mention 11025 and 12000 sample rates for
various modes, so I can assume that the sample rates are converted
within WSJT-X?
Resampling or "downsampling" is done many times in the chain of DSP
steps leading up to the actual decoder. These steps (which may overlap
somewhat, depending on the mode) include signal detection,
synchronization, and demodulation. Downsampling eventually ends at the
mode's symbol (or keying) rate. For WSJT slow modes these rates are
1.46 to 6.25 Hz, see Table 4 here:
http://www.physics.princeton.edu/pulsar/K1JT/wsjtx-doc/wsjtx-main-1.9.0-rc2.html#PROTOCOLS
The protocol descriptions mention 11025 and 12000 Hz because these rates
help to define exactly how the codecs are designed. They are convenient
rates at which to describe the modes, but not requirements.
-- 73, Joe, K1JT
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________
wsjt-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/wsjt-devel
