[TowerTalk] Cage Vertical

[WA3GIN]

...Just completed a cage vertical for 40m.  Used 1/2" PVC tubing
configured into a hoola hoop about 2ft in dia.  Used six wires equally
spaced around the hoop.  Used Ham Rope to suspend the hoop from a tall
branch.  At the base of the cage vertical I use another hoop same
material and diameter and bring all the wires together.  The top of the
cage is held in place with a counter weight so the tree limb can move
and not snap the wires, etc.

The bottom of the cage is connected to an insulator and tided off to a
ground rod.  The ground rod is the connection point for 48 1/4 wave
radials.
A impendence matching coil (cut to match the low impedance of the
vertical is made from #12 gauge solid copper wire and connected between
the cage vertical feed-point and ground. I resonanted the cage with an
MFJ 259.

I started with just 4 radials, the antenna provided a perfect 52 ohm
match (not good).  As I added radials the impedance went down down down
and settled around 29 ohms. With the matching coil in place the antenna
is about 2mhz wide. The entire ham band is flat 1:1

I expect similar results can be obtained with 1" PVC pipe used for
bringing well water to the house. Making the cage a bit larger to ensure
the wires do not contact the tower.

Good Luck,
Dave
Wa3gin


-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Barrie Smith
Sent: Sunday, July 17, 2005 7:28 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Cage Vertical

Since I'm planing to shunt feed a 70' tower before this coming fall, I'd
be 
very interested in discovering good information on the cage-vertical.

I've done several Google searches and have come up with very little in
the 
way of details.

Any help?

73, Barrie, W7ALW 
_______________________________________________

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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