K1: KAT1 -- cannot reach 5.0W output when adjusting R1 after calibrating power

[KB3OKS - Mark]

Has anyone run into this problem when finishing up their KAT1 ATU? I
was unable to find similar descriptions here.

I built the RF probe in order to calibrate power with the KAT1 and
have verified that the probe matches the schematic described in the K1
manual. Following the steps in the KAT1 manual, I set the ATU menu
entry to CLP (calibrate power) and then exit the menu, set output
power to 5.0 watts, set the K1 to use its lowest band (40m in my
case), and check that R1 and R2 are set to 60% of their travel (about
1 o'clock).

RF probe tip taps the center conductor of my 50 ohm dummy load, and
the negative is clipped to the dummy load's chassis.

After entering tune mode, I'm able to reduce power with WPM - (it
starts out reading about 24 VDC) until I reach about 14.0 VDC on my
DMM as described in the manual.

[The problem:]
The power out display on the K1 is now showing about 1.0. Adjusting R1
even all the way to its max will only display 3.8 at the point where
R1 is maxed out. I'm unable to reach 5.0. If I then exit tune mode and
check my power out setting in the OUT menu setting, it's down around
1.0, plus or minus a few tenths.

Has anyone else experienced anything similar? I've re-read everything
but can't seem to find a missing link.

Thanks very much and 73,

Mark / KB3OKS
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[KB3OKS - Mark]

I believe I solved my KAT1 power calibration this morning, so this is a follow up post just in case anyone else ever runs into this problem and searches this forum.

The solution was actually in re-checking my setting for the voltage null in trimmer cap C9 in the step prior to power calibration. On the advice of a friend of mine, I first decided to go way back to re-peaking the receive and transmit of the K1-4 filter board (minus the KAT1 tuner) just to make sure I wasn't selling myself short there. Things were still good, but I took my time with those steps anyway just to make absolutely sure that the settings of all the trimmer caps on the filter board were in their optimum positions. If nothing else maybe I improved things just slightly from where they were.

Back at the KAT1 testing, I was still getting the same result with the RF probe and setting of R1 -- turning R1 to its maximum travel was still only showing about 3.8 watts out. So I backed up a step and re-checked the setting of C9 for the voltage null. I felt good about it the first time I'd gone through that step, but who knows ... maybe I didn't have as good a connection as I thought with my probes at TP1 and the ground jumper.

In any case, power calibration this time around gave much better results. I only had to turn R1 to about the 2 o'clock position (only a little farther than it was already turned according to the instructions) to achieve 5.0 watts on the display. At its maximum, it was displaying about 8.5 watts! That also matched up with my friend's description of his KAT1 testing.

So now I'm off to check the KAT1 with a real antenna. SWR with my dummy load (clocking in at 49.5 Ohms) shows 1.0r ... so far so good.

Good luck to everyone else with their respective builds and testing in the meantime. Looking forward to hearing and QSOing with all of you down the log.

73,

Mark / KB3OKS

KB3OKS - Mark wrote

[The problem:]
The power out display on the K1 is now showing about 1.0. Adjusting R1
even all the way to its max will only display 3.8 at the point where
R1 is maxed out. I'm unable to reach 5.0. If I then exit tune mode and
check my power out setting in the OUT menu setting, it's down around
1.0, plus or minus a few tenths.