Well, I had really hoped to be able to share a success story about detuning
booms, but unfortunately all I can report is a 'result'...
Situation:
KT-36XA at 80 feet, 8 feet above a 40-2CD on a swinging gate mount. Both
antennas can rotate, independently. As I have reported here before, there is a
significant interaction where the SWR on the 40 rises to 2:1 when the boom of
the XA is parallel to the elements of the 40. (i.e. antennas aiming 90 degrees
apart).
Experiment:
As part of a recent rebuild of the XA (let me know if you want details), I
added wires from the boom joint bolts back to the boom/mast plate area. I
tested this with a variable capacitor on the ground, and found that a 200pf
variable would resonate nicely at 7.150. I built the capacitor into a
weatherproof enclosure. The XA has subsequently been reinstalled, and today I
went up the tower to install the capacitor. While at the top, I was able to use
an Autek RF-1 to get a very nice series resonance with the capacitor and the
boom of about 9 ohms minimum (a la W8JI references). I removed the RF-1 and
connected the capacitor in parallel with the boom wires.
Result:
No discernable difference in SWR behavior. I had hoped this would break up the
resonance enough to allow the 40 to think the XA was not there. Obviously I
missed something.
73,
Tony, K1KP
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