N4KG comments inserted below.
On Tue, 24 Apr 2001 09:04:02 +0000 Dave Hachadorian <email@example.com>
> The 40-2CD works well aligned with a nearby tribander. Mine is
> only 6 feet above the tribander. The loading coils in the 40-2CD
> elements move the third harmonic resonance to about 18 Mhz. In fact,
> the 40-2CD makes a very good 17 meter antenna, with a deep null off
> the sides, and swr ~ 2.
Do you see 6 lobes on 17M on your 40-2CD when you rotate it?
If so, then it is acting as 3/2 WL current fed Long Wire.
If you only see 2 lobes (broadside to the DE), then it is
acting as an isolated (as opposed to trapped) DIPOLE.
de Tom N4KG
> The only thing you need to worry about on the 40-2CD, and probably
> any close-spaced beam, is the random length of feedline dangling
> off the driven element of the 40, while the tribander is being used.
> This feedline can shift the resonance of the 40 driven element into
> the higher ham bands. A good way to test for this effect is to
> repeatedly short, then open, the 40 meter feedline, while observing
> swr on the tribander to see if it changes. If it does change,
> experimentally change the length of the 40 feedline.
AGREE. de N4KG
> Dave Hachadorian, K6LL
> Yuma, AZ
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