[TowerTalk] parasitic 4-square for 40 meters

[G.E. Tucker]

Yes, the 1/2 wave dipole sloper array was described in an older (70s/80s)
ARRL antenna book, I believe.

I happened to find a web site by a W4 on the Internet that described using
this idea to make a 2 element fixed delta loop (40M) beam using trees for
support. An Ameritron switch (RCS-8V) switchs both coax shield and center,
to open the 1/8 wave coax feed going to the box to make that element appear
longer, as a director, so you can have 2 beam directions.

I tried this idea but used dipoles instead, to make a 2-element wire yagi
supported from trees. I first did one for 40M and then one for 30M. The 40M
one is only up about 45 feet or so, but the performance is about the same
for Europe as a 40M four square I have (Array Solutions phasing
unit/controller) beaming in that direction (60 1/4 wave radials under each
vertical).

Particularly for someone who has taller trees around to support them, I
would suggest maybe two of these 40M 2 element wire Yagis, as that would
give 4 switchable directions, and not having to worry about radials,
phasing, etc. Or just put one up quickly to see how it works, and go from
there.

73, George W5VU (Massachusetts)


----- Original Message ----- 
From: "W0UN -- John Brosnahan" <shr at swtexas.net>
To: <towertalk at contesting.com>
Sent: Monday, February 21, 2005 1:54 AM
Subject: Re: [TowerTalk] parasitic 4-square for 40 meters


There was the 1/2 wave dipole sloper array that drove any
one element and terminated the others in long enough
coax so that the open end reflected enough inductive
reactance to the other elements to make them all
reflectors.  I believe it was published for 40M and I built
one for 20M to test it and it was OK, but my 2 element
quad at the same height that I added later was much better.

These were dipoles rather than vertical monopoles, but I am
sure the concept would work if you optimized the spacing and
tuning for parasitic elements.  But you still needed to switch both
the center AND shield so that parasitic reactance on the common
shields would not have a detrimental effect on the tuning.  So the
Ameritron switch would not work since you needed DPST relays
to do the job.

I think this antenna was in the older ARRL antenna handbooks
or possibly in an early ARRL Antenna Compendium.  Seems like
I built mine in the mid-1970s -- so that is the right era to look
for the published version.  I have never seen a monopole version
though.

--John   W0UN


At 12:42 AM 2/21/2005, Jan Erik Holm wrote:
>What is a "parasitic 4 square"?
>As far as I know there is no "parasitic" with a
>4 square since it´s a driven array.
>Did I miss something new??
>
>73 SM2EKM
>----------------------------------
>
>Ron Feutz wrote:
> >>TT'ers
> >>
> >>I have everything I need for a parasitic 40 meter 4-square but can't
find
> >>design info.
> >>
> >>I want to try this antenna as my marginal cost will be zero.  I have 4
33'
> >>verticals, an Ameritron RSC 8-V switch and plenty of radial wire and
coax
> >>on hand.
> >>
> >>Any info on design and tuning will be appreciated.  I believe the design
> >>has 3 "reflectors" that use the inductive reactance of the open feedline
to
> >>make them "reflectors,"  right.  How long should the feedlines be?  I
can
> >>tune with the MFJ 259B.
> >>
> >>Any models out there to tell me what to expect?
> >>
> >>Archive and google search turned up nothing.
> >>
> >>73,
> >>
> >>Ron KK9K
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk


_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.

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