[TowerTalk] parasitic 4-square for 40 meters

[Jim Lux]

I imagine what you're thinking of is a square array of antennas, where you
feed one, and either ground or open the remaining elements.

This would be a bear to compute from first principles, so your best bet is
to get a program that has an optimizer combined with NEC (I use 4nec2...
google and you'll find it).  You can set up a model with the 4 vertical
elements (I think there's already one there), then add the transmission
lines. Use a "SY" symbol card to create a symbol for the transmission line
length.

Then, fire up the optimizer and use the F/R or F/B as your figure of merit
and let it adjust the TL length.

A couple useful tricks.  You're going to want to have a minimum TL length,
so what you really want is two TLs in series.  The first one is the minimum
length, the other one is the one that's optimized (which might go to zero).

There are some interesting switching possibilities...(not all possible with
the RCS-8V, which can ground or open a given "unselected" port, but not
both)

Another approach is to drive a pair, and open/short the other pair.  (Why
not pick up an easy 3dB of gain?)

Another strategy is to drive two diagonal elements (in parallel), short one
and open the other.  With the right lengths, one of the elements will be
"long" and the other "short".

You'll also probably need a tuner, since it's unlikely the impedance will be
a nice 50 ohms.

An hour with 4nec2 will answer all your questions, though.


----- Original Message -----
From: "Jan Erik Holm" <sm2ekm at telia.com>
Cc: <towertalk at contesting.com>
Sent: Sunday, February 20, 2005 10:42 PM
Subject: Re: [TowerTalk] parasitic 4-square for 40 meters


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