K3 PSK31 threshold/ 10W amp duty cycle.

[lstavenhagen]

HI all,
2 quick questions:

I did a search through the firmware release notes and didn't see anything about the PSK text decode threshold feature being enabled. Still seems non-functional in my K3 (which has the latest FW), so I assume this still isn't implemented?

Second, I couldn't find much about the full power duty-cycle of the K3's 10 power amp. I'm curious if I shouldn't run full blast on data modes, i.e. back off to 5W?

Meanwhile, still trying to find something wrong with mine on my lunch break and so far no success. I went to Best Buy and got their Bill-n-Ted's Excellent USB -> RS-232 adapter with my fingers crossed hoping it used the Prolific chipset. Sure enough it did.  So DL'd the MacOS X drivers and K3 utility off Elecraft's site so now my laptops can talk back and forth to the rig. Next I might try getting it working with CocoaModem.

73,
LS
W5QD

[Julian, G4ILO]

The K3 is rated to withstand 10 minutes at full power key down. Eric confirmed a few months ago in answer to a question by me that applies to the 10W version as well as the 100W version.

lstavenhagen wrote

Second, I couldn't find much about the full power duty-cycle of the K3's 10 power amp. I'm curious if I shouldn't run full blast on data modes, i.e. back off to 5W?

[K1LI]

To change PSK31 text decode threshold, press and hold CWT to enable TEXT DEC and rotate the main VFO knob to change the threshold.

[Richard Ferch]

LS,

With respect to power in PSK, I'd be just as concerned about signal
quality (IMD, splatter) as about the power handling capability of the
finals. PSK is extremely sensitive to IMD.

Instantaneous peak power in PSK can be twice the average power. Even if
the amplifier is within its thermal ratings at full power, if
instantaneous peaks are clipped your transmitted signal will have
increased IMD. Operating below half the rated power should be OK, but
you might want to do some on-air IMD testing before routinely using
powers above half the rated power in PSK.

RTTY is a different story. The main issue in RTTY is not IMD, it is
keying transients. These are visible as peaks in the frequency spectrum
separated by multiples of the 45 baud keying rate. In the limited
testing I have been able to do, I have not noticed any sensitivity of
RTTY keying transients to output power.

What I have seen, however, is that my K3's AFSK signal is cleaner than
the FSK signal - it's not that the FSK signal is bad, just that the AFSK
keying transient peaks are lower. I believe Chen W7AY has made similar
observations.

73,
Rich VE3KI
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