Posted by
Richard Ferch on
Feb 15, 2009; 4:30pm
URL: http://elecraft.85.s1.nabble.com/K3-Beta-firmware-rev-2-80-Improvements-to-AFSK-A-DATA-A-SSB-AM-FM-DVR-tp2305650p2330339.html
It seems as if part of the problem with the power control in DATA A mode may
be that the power calibration appears to be done at an audio frequency which
is sub-optimal for this mode. Ideally, the power calibration would be done
at the point in the filter bandpass where the transmit filter's attenuation
is least. If this were the case, the delivered power would be equal to the
requested power at the optimal frequency, and equal or less at other points
in the filter bandpass. Delivered powers exceeding the requested power would
not happen. Lower output powers would be possible, especially towards the
edges of the bandpass, but this is normal and happens with every radio, not
just the K3.
Performing power calibration at the transmit filter's optimal frequency
might be sub-optimal for CW, though, because of the way the filter bandpass
is adjusted during CW. If this is the case, perhaps there should be separate
power calibrations for CW and for data modes.
As it happens, there is another anomaly in DATA A which has some
similarities to the above, although this may be coincidental. The SPOT
button in other digital modes produces an audio tone at an optimal frequency
(the selected mark tone in AFSK A and FSK D and the transmitted tone in PSK
D), but in DATA A the SPOT button produces a tone at the CW sidetone pitch.
The CW sidetone has nothing to do with DATA A mode, and it is far from the
optimal point in the filter bandpass in DATA A. Just as it would be better
to do power calibration at an optimal audio frequency, it would be better if
the SPOT button produced an optimal tone. Good candidates for an optimal
tone in DATA A would be either the current filter Fc or the default ("NORM")
Fc for DATA A (1500 Hz).
73,
Rich VE3KI
K3 #1595
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