Simpler maybe is just drop the ends of the dipole straight down to make it
fit the available space?
I have done it many times and I don't believe there is any sacrifice in
performance.
It does require the total length of wire to be increased a bit.
73
Tom Hellem
K0SN
On Sun, Dec 22, 2024 at 8:09 AM Stan Stockton <wa5rtg@gmail.com> wrote:
> A few months ago I designed and my son built a 2L 40m Yagi using this type
> of design for loaded elements inspired by the W6NL style Moxon since that’s
> what he was going to build. The results are virtually the same in terms of
> gain, pattern, etc., but it is not as unwieldy and reduces the weight out
> on the element that causes it to sag excessively. TBD, but I believe it is
> less likely to interact with a 15m antenna.
>
> I have the need to put up a 40m dipole between a couple of towers here at
> ZF9CW. If the towers were about 20 feet farther apart I would just put up
> a flat dipole but they are a little close spaced for that. The element is
> going to be less than 50 feet long and it will be 50 ohm direct feed as
> opposed to about 75 ohms if it were just a normal dipole.
>
> For those who want to put up a dipole for any band, do not have the room
> for a flat dipole and do not want to either do some impedance matching with
> a 12th wave transformer or live with 1.5-1 SWR at best, here are the
> details of what I am going to find the time to do on 40 meters. I will be
> limited to using the materials on hand. I would rather use #14 wire.
>
> 49 feet total (24-1/2 feet either side of center) of #16 wire fed in the
> center. At 15 feet out from center on either side there will be a 6 foot
> piece of 3/8” aluminum tubing that will be electrically connected in the
> center to the wire which will continue out for another 9-1/2 feet. So there
> will be 3 feet of aluminum tubing either side of center. From the ends of
> the aluminum tubing there will be #16 wires that will connect to the end of
> the wire (24-1/2 feet out). Those two wires should be ever so slightly
> slack so when the dipole is pulled up to its flat position there won’t be
> any significant stress on the ends of the aluminum tubing.
>
> If you just draw this on paper it looks like a dipole that is 20 feet
> shorter than a normal dipole and near the ends you have what looks like an
> arrow.
>
> I have this skewed a little toward the bottom end of the band, but about 4
> inches shorter overall length would give you less than 1.5-1 from 7.0 to
> 7.225.
>
> The gain of this dipole is about 1/4 dB less than a full sized dipole.
> Its bandwidth between 1.5-1 points is about 25 khz less than a full sized
> dipole but only if you do a perfect job of matching your 50 ohm coax to the
> higher impedance of the full sized antenna.
>
> I probably won’t do anything other than write this but if I get inspired I
> might sometime write it up for a magazine. I can see great benefit for
> those with limited space. A flat dipole is so much better than what’s
> commonly referred to as an inverted V.
>
> I’ll be glad to send an EZNEC file to anyone who wants to get a better
> picture of the design. Just send me an email.
>
> 73 and Merry Christmas.
>
> Stan, K5GO/ZF9CW
>
>
>
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