On 01/01/2018 10:10, Peter Connors wrote:
I first installed WSJT (first 10 then 9.7) I read the user manual and
got ready to calibrate the audio feed.
I started with the same 48kHz 16-bit input I had been using for WSJT-X
and was intrigued to notice that, with the Rate in and Rate out still
set at 1, the 'lower left' numbers varied between only 1.0001 and
0.9999. At the next moonrise it was decoding and displaying well and
remains so.
Have I entered a chronosynclastic infundibulum?
Pete G4PLZ
Hi Pete,
WSJT requests 44100 Hz audio streams whereas WSJT-X requests 48000 Hz
audio streams. Both will work with the sound card default sample rate
set to either but not having the default set at the same as the
application's requested rate will cause the operating system to
re-sample the streams to achieve he desired rates. Such re-sampling is
not optimal as the two rates are not related by an integral factor. If
you mainly use WSJT I recommend setting the sound card default rate to
44100 Hz 16-bit and if you mainly use WSJT-X set the sound card default
sample rate to 48000 16-bit. Setting a higher rates that are related by
integral factors with the desired rate (e.g. 96000 Hz or 192000 Hz when
a 48000 Hz stream is required) will not degrade the audio quality but it
gains nothing either. Similarly selecting 24-bit samples loses nothing
but gains nothing either as the lower 8-bits of each sample will be
discarded when a 16-bit stream is requested.
Small random variations in the measured sample rate are probably due to
varying software latencies rather than sound card sample clock jitter or
error and can be ignored, OTOH consistently greater than or less than
unity indicates a clock accuracy issue that you can correct for in WSJT.
73
Bill
G4WJS.
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