[TowerTalk] Fw: Make a 6M halo antenna- K0FF

[K0FF]

Repost due to multiple requests. Geo
-----Original Message-----
From: K0FF <K0FF@ARRL.NET>
To: Tower Talk (mail list) <towertalk@contesting.com>; VHF reflector
<vhf@w6yx.stanford.edu>
Date: Tuesday, May 23, 2000 11:38 AM
Subject: Make a 6M halo antenna- K0FF


>Here is the parts list and dim. sheet for a 6m Squalo, made from copper
>water pipe. It is more or less omni-directional, and horizontally
polarized.
>It presents a high angle of takeoff when mounted low, and singly (great for
>Es), and can handle 100W.
>It's just a dipole folded around on itself, and supported at the far end
>with a plastic insulator.
>The shape is a closed 28" square, with a mounting bar through the middle.
>This mounting bar is attached to a copper TEE at the drive end, and to a
>PVC TEE at the other end. The PVC TEE acts as support and end-insulator for
>the radiating element. A large (3/4") part is used, and adapted down to fit
>the water pipe, to increase it's insulating qualities, as there is very
high
>voltage at this point. A strip of brass or copper 1/2 by 3" is screwed to
>the outside middle portion of the PVC Tee, through a small center hole, and
>is rotated one way or the other as a resonance tuner(butterfly). A gamma
>match sets the impedance to 50 Ohms, and the butterfly adjusts the center
>frequency.
>A U bolt and saddle through the central tube provides a center mounting
>point. Another approach is to install a copper TEE in the center tube, with
>the open end down. In that open end solder a 1/2" brass rod which has been
>drilled and tapped for 3/8-24.
>Side mounting on a tower can be achieved by using conduit clips to fix it
to
>a horizontal mast.
>
>Material:
>1/2" Cu waterpipe :
>3 ea. 27 inch piece
>4 ea. 12.5 inch piece
>
>3/8 i.d. Cu refrigeration tubing :
>1 ea. 13.5 inch piece (p/o gamma)
>
>Brass plate: 1"x 2-1/2 in (to mount so-239, gamma rod)
>
>4 Cu 90 Degree elbow
>1 3/4 PVC TEE
>1 3/4 to 1/2 PVC reducer
>1 Cu TEE
>
>Glue two of the 12.5" pipe sections into the PVC reducers first, then glue
>the reducers into the opposite sides of the PVC TEE.
>Lay the assembly on a flat surface with the center opening of the TEE
>facing the middle of the antenna. This is where the first 27" piece
>(mounting
>bar) goes in, via a reducer. On the outside edge of the PVC TEE is where
the
>
>butterfly attaches. For mobile or portable use, use 3 s.s. #6 screws
through
>each of the PVC TEE joints for added strength.
>The rest of the antenna solders together to form a square, using the 90
>degree elbows at the corners.
>The brass plate is bent to form an "L" 1-3/4"  tall with a 1/2" lip. A 5/8
>hole is provided 1-1/4 inch from the bend, and an so-239 is attached . Two
>small holes are drilled in the lip and the plate is mounted to the copper
>TEE with #6 s.s. self taping screws. Solder the center conductor of a 11"
>piece of RG8 insides (center wire and plastic dielectric only- remove and
>discard shield and outer covering). Slip the RG8 insides into the 3/8"
>copper tube 10.5", and tap the copper tube to the radiating element 13-1/2"
>from
>the so-239 center, with a copper strap.
>
>The tap on the Gamma sets the impedance presented to the feedline.
>Resonance (center frequency) is adjusted by turning the butterfly.
>
>
>Mount 15 feet or more high, for home use, and wherever you can for mobile.
>An antenna like this can be mounted 3" to 6" above the roof of a vehicle
>using PVC or acrylic spacers with suction cups.
>
>
>Have fun on 6. K0FF
>
>
>


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