[TowerTalk] Make a 6M halo antenna- K0FF

[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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