Who makes the 131 foot crankup tower that's capable of supporting multiple big
antennas like those two? I'd like to have one, too...
>From: Dan Hearn <email@example.com>
>Sent: Mar 12, 2008 12:06 PM
>To: T talk <firstname.lastname@example.org>
>Subject: [TowerTalk] 30m/40m Yagi Ideas?
>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
> 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
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