Phil:
I have a K8UR configuration 4 square on 80 mtrs which hangs off the 120' guy
ring on my rotating tower. Based on my own experience, I'm suspicious of
your SWR readings. The antenna simply cannot be that flat over a 100 KHz
bandwidth.
Also, when I was building mine I was anticipating an upward shift in
resonance due to the mutual coupling of the four antennas. On the K8UR
configuration, this does not happen. . . so you don't want to follow the
general rule of thumb of starting out with antennas that are low in
frequency. I cut my dipoles by the formula for 3.490 thinking the array
would shift upward by 5% or so. I installed the first one and it was
resonant at 3.490 per the formula. I added the other three. . . the
resonant frequency of the array didn't change (measuring resonance as the
minimum power dumped to the dummy load). I'm getting 2-3 watts into the
dummy load with about 90 watts delivered to the Comtek box. . . but
certainly not over a 100 kHz window. I'd have to say something else is
influencing your readings.
73 and good lowband DX this season to all. . . Dave
W0FLS
-----Original Message-----
From: Phil Clements <philk5pc@tyler.net>
To: towertalk@contesting.com <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Monday, September 27, 1999 12:50 PM
Subject: [TowerTalk] Tuning the K8UR-Style 4-Square
>
>On page 11-79 of ON4UN's 1999 book, Mike, K4PI
>uses vacuum relays to switch about 6 feet of wire on
>each of his 4 dipoles at the ground level to QSY his
>K8UR-style 4-square from the SSB DX window to the
>CW DX window on 80m.
>
>Since my version was resonant when installed at 3622 khz,
>I cut 5 feet off the bottom end of each dipole to QSY the
>array to 3770 khz. My "window of resonance" on this array
>is 100 khz. IOW, the power to the dummy load on the Comtek
>box is zero from 3713 to 3813 khz.
>
>All this sounds really good, but could this be good VSWR for
>all the wrong reasons? I now no longer have 4 symetrical dipoles,
>but 4 off-center-fed dipoles. What has this done to the pattern
>and or the Comtek box? Has anyone run any modeling on a
>situation similiar to this one? Please share any of your experiences.
>
>(((73)))
>Phil, K5PC
>
>
>
>
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>
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