[Antennaware] Fwd: HF Colinear Dipoles

[Terry Conboy]

> From: Terry Conboy <n6ry at arrl.net>
> Subject: Re: [Antennaware] HF Colinear Dipoles
> Date: 2019 August 27, at 6:44:24 PM MST
> To: Karin Johnson <karinann at 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 at tampabay.rr.com <mailto:karinann at 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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