K3 High SWR

[Larry P. Greenberg]

My K3 (modified to K3s) is giving me a problem for the first time in ten
years.  I first noticed it driving the KPA1500 erratically. It would go from
a few hundred watts to excessive power and faulted out.  In order to narrow
down the problem, I disconnected the K3 from the KPA1500 and put a dummy
load on the K3.  Under 12 watts, the K3 worked well.  Over 12 watts, the K3
showed high SWR increasing as the power went up.  The cooling fans turned on
indicating something was getting warm.  I put the dummy load on Antenna 1
and Antenna 2, selected them and got the same results.  I then did a
Transmitter Gain Calibration which failed the 50 watt, high power
calibration but passed the 5 watt calibration.  

 

I called Elecraft Technical Support but they are short handed due to
numerous people being out with the flu.  I wonder if anybody has any ideas.
I'm thinking it's a sticking relay or a PIN diode possibly after the finals.


 

Larry, WA9MAG

 

 

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

[DL9HDA]

Hello, I have exactly the same problem.

I never noticed this because I only ever run my KPA500 at 400W in CW. For this only 12-15 W are necessary.
But during a test without PA then the error was noticed.
Above 12W the SWR increases with increasing output power. The real output power is much higher than it should be.

What is the solution?


73, Holger DL9HDA