[CQ-Contest] 10/15 interaction

Georgens, Tom Tom.Georgens at netapp.com
Thu Nov 6 16:01:02 EST 2014


I am not sure what stubs you have on the feedlines but I had a similar issue at my station.

I have a 20 meter monobander about 6 feet above a 15 meter monobander.  When I transmit on 15, I was overloading the receiver on 20 despite having bandpass filters in both lines.  The higher frequency signal getting returned on the lower frequency antenna is a common problem

What fixed it was an open stub on the 20 meter feedline to trap the 15 meter signal.  I think the math was a 1/2 wave on 20 and 3/4 on 15.  This worked great.  A shorted version, full wave on 10 and 3/4 on 15 should do the same thing for you.

Good luck

73, Tom W2SC 8P5A

-----Original Message-----
From: CQ-Contest [mailto:cq-contest-bounces at contesting.com] On Behalf Of Randall K Martin
Sent: Thursday, November 6, 2014 10:34 AM
To: cq-contest at contesting.com
Subject: [CQ-Contest] 10/15 interaction


Thanks for all the quick responses. Here is a summary of what I've heard so far.

1) I am already using coax stubs on both the 10M and 15M feedlines, and I believe these are working. I do not have a 15M reject stub on the 10M feed, so this is a good suggestion and I will try it.

2) Kelly VE4XT had a good suggestion to add a choke balun on the 10M yagi in addition to the standard KLM balun that is already in place to see if this will help. The 10M feedline runs down through the plane of the 15M yagi. WX is nice here and I can easily try this.

3) There may be less interaction when the yagis are 90 degrees from each other, but in almost all situations, I am pointing them in the same direction. Also, my goal is to eliminate the HI RFI problem from happening in any scenario.

4) Getting rid of the K-3's is not something I would consider.

5) The antennas are both 6 element KLM big stickers, both with standard KLM feed baluns of that era.

73 Randy K0EU

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