PX3 Possible Bug - Refresh Rate Slow Depending on KX3 Digital Mode Selected

[ve3ibw]

Received a PX3 for Christmas.  Have been very happy with the unit.

However, I noticed what appears to be an inconsistency.  What I have
observed is that at certain spans (e.g., 2, 5, and 10), the PX3 refresh
rate appears to slow down depending on the KX3 digital mode selected (e.g.,
AFSK A, Data A, PSK D, FSK D).  Yet, the PX3 refresh rate is always 80ms
when I check for each span/mode combination.   PX3 Text display, waterfall,
and spectrum scope all enabled with MKR A on.  KX3 is set to 14.070Mhz,
AGC-F, VOX, FL2.

What I mean by slow is of course anecdotal; it is my perception, not
measured.  At say a span (PX3) of 2 and data mode of PSK D (KX3), the
waterfall and spectrum scope appear to be refreshing at a rate I expect
based on first impressions with the PX3 out-of-the-box.  But, if I change
the KX3 data mode to DATA A, the PX3 refresh rate appears to slow down
considerably.  The same slow down occurs when I change to AFSK A.  But,
when I move to FSK D or PSK D, the PX3 rate appears to return to a more
normal speed.

However, this pattern changes when I switch the PX3's span to 5.  Now, KX3
PSK D and FSK D data modes seem to have slower PX3 refresh rates than DATA
A and AFSK A.  Finally, moving the span to 10, I observe the opposite, but
not as pronounced; more like the pattern when the span was 2.

At a span of 20 and above, I don't notice the difference between the PX3
refresh rates at different KX3 data modes.

I have firmware:
KX3 - 2.27 / 1.30
PX3 - 1.16

regards,
Brian
VE3IBW
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[Paul Saffren N6HZ]

Hi Brian,

The slower refresh rate at narrower spans is normal.  The reason is that at these narrower spans (below 24 KHz) we effectively down sample the I/Q stream.  Down sampling requires the PX3 to acquire many more samples for each screen which directly affects the refresh rate.  

The sampling rate is tied to the SPAN, and the SPAN setting is stored per MODE.  Verify that as you change digital modes, the span stays the same.   My guess is that the span set for USB is different than LSB and this becomes the issue as FSK uses USB and PSK uses LSB.

Kind regards,

Paul