[CQ-Contest] 10/15 interaction - No More

Randall K Martin rkmassoc at comcast.net
Fri Nov 7 16:08:04 EST 2014

I want to thank all of you for your great insight on my problem with the 
10M monobander transmit power getting into the 15M monobander line. It 
turns out that adding a simple reject stub for 10 and 20 meters (shorted 
1/4 wavelength at 7 Mhz, approx 23 feet long) took care of the problem.

I am embarrassed to admit that, prior to fixing the problem, I took 
someones suggestion and measured the RF power coming in on the 15M coax 
at the amp input when transmitting on 10M at 1500W. I found almost 20 
watts! I should have checked to see what power was making it past the 
dunestar 600 at the rig output, but it is a moot point now. In any case 
it is no wonder the K-3 was complaining.

Inserting the stub dropped the power to where there is no perceptible 
reading at the 20W scale on the elecraft meter.

Thanks especially to OH6LI, W2VJN, and K6LL for steering me towards the 
10/20 reject stub.

73 Randy K0EU

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