Wednesday, September 28, 2011

80/75 Meter 4-Square Array

80/75 Meter 4-Square Array

The SWR from 3.5 to 3.9 is below 1.5:1
The F/R of the array is 20dB average and with some signals even better.
The radial system consists of 90 1/4 wave long wires attached to the base of each vertical.
Close-up picture of the support post and base of the vertical.
Each vertical is mounted on a 6 inch square by 12 foot long pressure treated post.
The posts were buried 4 feet in the ground.

The verticals are 65' tall. 40 feet of 4" and 25 feet of 3" aluminum irrigation tubing. The joint overlap is 1'.
I have replaced the UV resistant bale twine (guy ropes) with 3/16" (770lb. tensile strength) UV resistant Dacron rope.

Support Post Detail
Each support post is 6" x 6" x 12' pressure treated. 4' of the post is in the ground..
The vertical is insulated from the post by PVC electrical conduit.
The support arms are made from 1/2" thick Plexiglass (Acrylic) sheet.

Joint Construction Detail
I used a 1 foot overlap at the joint between the 4" and 3" tubing.
3-1/2" Sch. 40 Aluminum conduit (pipe) has to be machined to fit inside the 4" irrigation tubing. 3" Sch. 40 aluminum conduit (pipe) is used to transition from the 3-1/2" conduit to the 3" irrigation tubing. No machining required on this sleeve.


Check out these pictures of a thunderstorm that was a bit too close for comfort. Fortunately the cell didn't move directly over the array. It sure came close though.

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