> From: Terry Conboy <n6ry@arrl.net>
> Subject: Re: [Antennaware] HF Colinear Dipoles
> Date: 2019 August 27, at 6:44:24 PM MST
> To: Karin Johnson <karinann@tampabay.rr.com>
>
> The info in Ch 11 of ON4UN's book is almost all about verticals, so won't be
> of much help.
>
> I've attached four EZNEC models of a two element collinear dipole array for
> 20m.
>
> Two are just dipoles with separate current sources, one in phase, the other
> 180 degrees out of phase. This lets you see what the patterns are without
> worrying about the feed system. You can look at the feed Z of each antenna
> to see what you have to drive.
>
> The other two models have coax feed systems. When in-phase the two elements
> each have about a 100 ohm Z, so you can use two half-wavelength (or multiples
> of 1/2 wl) feedlines and just parallel them at the common point. They can be
> any impedance, but the losses and bandwidth will be best with 75 ohm lines.
>
> When out of phase, the elements each have about a 50 ohm Z, so you can use
> 3/4 wavelength 75 ohm lines to transform the impedance to 100 ohms so the two
> can be paralleled for a 50 ohm feed at the common point. (There are many
> other feed arrangements possible, too.)
>
> If you want to switch the patterns in the real world, you'll have to figure
> out how to switch the cable lengths and invert the phase.
>
> Let me know if this is what you're looking for.
>
> 73, Terry N6RY
>
> On Sun, Aug 25, 2019 at 1:57 PM Karin Johnson <karinann@tampabay.rr.com
> <mailto:karinann@tampabay.rr.com>> wrote:
> Hello Group:
>
> I would like to have a discussion off list about designing a 20 Meter
> Colinear dipole array.
>
> Right now I am trying some simulations in EZNEC and am referencing the Low
> Band DXing
>
> Book by ON4UN with regard to the Phasing of the two or multiple antennas.
>
> I'm having a bit of difficulty in replicating some the work ON4UN and the
> volume authors
>
> Did on the understanding of the Array Chapter number 11.
>
>
>
> Anyone who has tried building collinear antennas at HF?? I know that Tom
> W8JI has
>
> Done this on a massive scale and that is not what I am trying to accomplish
> here.
>
> Just two simple collinear dipoles fed either in phase or out of phase.
>
> The EZNEC simulations seem to blow up when the phasing and matching networks
> are
>
> Applied to the two antennas.
>
>
>
> Regards,
>
> Karin Anne Johnson K3UU
>
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