Re: K3 Beta firmware rev. 2.82

Posted by Julian, G4ILO on Feb 15, 2009; 9:32am
URL: http://elecraft.85.s1.nabble.com/K3-Beta-firmware-rev-2-80-Improvements-to-AFSK-A-DATA-A-SSB-AM-FM-DVR-tp2305650p2329220.html

Joe Planisky wrote

To test this, I used an audio signal generator to input single tones  
of various frequencies into my K3 in both LSB and DATA-A modes.  I set  
the power control for 30W.  Here are my measurements:

AF input freq. Po-DATA-A    Po-LSB
TUNE            25.7         25.2
  200             4.6          6.1
  400            27.0         24.8
  600            34.5         24.8
  800            45.6         24.8
1000            53.1         24.8
1200            47.5         24.8
1400            37.8         24.8
1600            32.3         24.8
1800            30.9         24.8
2000            31.9         24.8
2200            34.3         24.8
2400            37.9         24.8
2600            34.9         24.8
2800            13.9         24.8
3000             nil          nil

So, neglecting the ~25 W vs 30 W error, it's clear that something is  
keeping a tight rein on things in LSB, but is not doing so in DATA-A.  
Presumably, this is the ALC action, which we are told is minimized in  
DATA-A mode.  The data also seem to corroborate your statement that  
the calibration point is 300 Hz from the filter corner.

That amount of variability is alarming. I'm really not happy with it. But to me, that's not a 25W vs 30W error, it's a 30W vs 53W error. Because the output at 1KHz, which is the center frequency I use for PSK31, is 53W when 30W is requested. This is exactly what I am complaining about.

If the power output at 1KHz matched the power level requested then I would be a lot happier, though it is quite disappointing to see that the power would be little more than half that level over most of the range that a Digipan user would operate in.