Pete, adding the second C3 is a great idea...even better if it rotates.
Your spacing is a little close for 20, even with the short boom of the C3,
but will still be better than only the single yagi. I wouldnt worry about
the spacing on 10 at all. If anything you might want to add a yagi below
the 69 footer. As is, I think you'll find that most of the time the single
yagi at 69 feet will outperform the top one most of the time once the flux
starts climbing.
I'd recommend using a broadband transformer switching scheme such as the
WX0B Stackmatch for any situation involving mixing and matching of
multiband antennas.
73, Ty K3MM
To: Towertalk@contesting.com
cc: (bcc: Tyler G Stewart/BENN/CEC)
Subject: Re: [TowerTalk] Stacked tri-banders vs. Single mono-banders
I've been toying with adding a second C-3 at 69 feet to my current one at
97 feet. The 2-stack appears from modeling to be pretty decent for 20 and
15, but leave a lot to be desired on 10, given the over-wide spacing. Do
the assembled antenna wizards have any opinions on the idea of adding a 3
or 4-element 10-meter yagi halfway between the two tribanders? If I
understand things correctly, I would need to have odd 1/4 wave multiples of
feedline from the common feed point (UNUN box, presumably) to ensure that
all 3 antennas would get equal current on 10, despite their dissimilarity.
I'd also try to make the 3 driven elements line up with each other, more or
less, to mibnimize phasing errors from that source. On 15 and 20, the
10-meter antenna would be effectively disconnected, of course, but with the
two C-3s my hope is that feedpoint currents will be similar even if I can't
follow the 1/4 wave rule for them. Right/wrong?
Any opinions, caveats, things to avoid?
73, Pete Smith N4ZR
n4zr@contesting.com
"That's WEST Virginia. Thanks and 73"
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