Oops! Somehow my message got sent before I was done with it!
I would also encourage you to get familiar with NEC2 in some form (if
you are a windows person 4NEC2 is an easy way to get started, and if you
are a Mac or Linux person, there are other GUIs to use with NEC2).
Modeling is easier than doing it in the real world, though perhaps not
as much fun.
Anyway, I think your project should be an interesting one.
On Wed, 2008-03-12 at 12:06 -0700, Dan Hearn wrote:
> I am in the process of building a 2 element 2 band yagi for 30/40m. It will
> use some 20m elements, which I have, extended to full size on 30m. The
> elements will be coil loaded for 40m and the coils will be shorted with vac
> relays, which I have a good supply of, on 30m. Matching will be done using a
> 50/25 ohm balun/xfmr as available from DX engineering. My thought is to use
> coils at the center of each element but I realize the 40m efficiency would
> probably be greater if the coils were further out on the elements, probably
> at the junction between the 17 ft tips and the center tubing section.
> I plan to mount this antenna on the 2 7/8 mast above my 6 el 20m yagi.
> Spacing will probably be 10-12 ft. Height will probably be 142 ft on my 131
> ft crankup.
> I would appreciate any comments on this proposed design. I realize that a
> lot of my questions can be answered by modeling the design but I have no
> experience in that area. I am using the Taper program to come up with the
> element lengths and would rather spend my time building the antenna and
> putting it up, Hi. I will ultimately ask for help in determining the
> inductance values for element loading.
> 1. Would putting the coils out on the elements vs. at the center improve the
> gain enough to be worth the extra effort?
> 2. What would be a good compromize element spacing on the boom?
> 3. What do you think of using the 2:1 xfmr for matching? Seems to work for
> 4. Is there any place I can buy large type 31 ferrite cores, as used in
> K9YC's great balun designs on his web page, in small quanties? I might wind
> the 2:1 balun xfmr myself.
> Thanks, Dan, N5AR
> TowerTalk mailing list
Rob Frohne <email@example.com>
Walla Walla University
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