[Elecraft] K144XV on digital modes - disappearing power

[Gary Hembree]

This problem has nothing to do with setting the proper ALC level.  Both KB7Q and I have observed this behavior after carefully setting up our K3s for WSJT-X operation with the K144XV.  KB7Q found if he ran JT65 in USB mode the power setting behavior of the K144XV was normal but if he ran in DATA A mode it was anomalous.  I have had the exact same problem while running MSK144 in DATA A mode.  Both of us observed the same “cure” as Kjeld: slight movement of the power control restored normal power output.  Neither of us had this problem while running SSB or CW.  The two K3 transceivers we made these observations on were SN 7xx and SN 4611, which are widely spaced in date of production and board revision levels.  When KB7Q upgraded to a K3S, using the same K144XV module, the anomalous power setting behavior in DATA A mode did not occur.

I have a very strong suspicion that this problem is related to the new firmware that is shared by both the K3 and K3S.  It works correctly in the latter case but not the former.  Unfortunately I cannot revert to a pre-K3S firmware version.

73
Gary, N7IR


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Kjeld,

Are you driving the audio up to 4 bars on the ALC meter with the 5th bar 
flashing?  This is the "zero ALC" point for the K3, KX3 and KX2 
transceivers.

Without sufficient audio  The K3 will "power hunt", and that may be what 
is happening.

Refer to the article on my website www.w3fpr.com.  Scroll the left 
column down to the lat article and click on that link.

73,
Don W3FPR

On 2/25/2018 5:28 AM, Kjeld Holm wrote:
Dear Elecrafters,
For a year or so I have had an internal K144XV transverter for 144 MHz in my
K3. I have not been using it very much - just a few FM QSOs. I have not seen
any problems.
Now I have just started using K144XV on digital modes - especially FT8 (42%
TX and 58% RX).
I started out selecting 10W output. After 4 minutes the output suddenly felt
to a few mill watt.
Starting out with 5W or even 2W produced exactly the same result. 
But without regard to the starting point I could get normal output again
just by changing the output a little bit. It did not matter whether I
increased or decreased my power a bit.  
I did not hear any fans starting up and I could not feel any heating at any
sides of the K3. 
Can anyone explain what is going on - what I am doing wrong - what I can do
to keep the output stable? 
Vy 73 de OZ1CCM, Kjeld