Antenna was designed by Kent Britian, WA5VJB, and full credit (and blame)
belongs to him on this design!
This antenna is ideal for rovers, and is good for a fixed station on a budget. It can be built for around $15-20 (1999 dollars).
The boom material typically is wood, 1/2" by 3/4" sold in home centers as "flat pine molding". 3/4" x 3/4" solid molding is usuable as well. There is little reason why fiberglass tubing wouldn't work as well.
Outdoor varnish, paint or deck stain will work to weatherproof the antenna. Put a dab of RTV over the coax connection after verifying the SWR of the antenna.
Elements can be secured as WA5VJB suggests, with epoxy or RTV, or alternatively as I do: I file a small groove around each element very close to where it protrudes out of the 1/2" wooden boom (on each side), and force on "push-nuts" (also called "speed-nuts") on each side of the element for a positive hold.
On the center conductor, solder a small brass washer or nut onto the "J" shaped side of the element before mounting, and clip the "push-nut" to the other side upon mounting on the boom.
I usually also wind a small loop of the RG-58 coax into a small RF choke under the feedpoint to act as a balun. WA5VJB states that this step is unnecessary, but I'm a purist...
Element Lengths and Spacings in Inches:
144 MHz. This antenna is peaked for 144.2 MHz but performance
is still good at 146.52 (emergency use only!) Driven element dimensions
are L = 38.5" and H = 1.0" Elements are 1/8" diameter.
|144 MHz||Reflector||Driven||Director 1||Director 2||Director 3||Director 4|
222 MHz. This antenna is peaked for 222.1 MHz but performance
bearly changes at 223.5 MHz. Driven element dimensions are L = 24.5" and
H = 1.0" Elements are 3/16" diameter.
|222 MHz||Reflector||Driven||Director 1||Director 2||Director 3||Director 4|
432 MHz. This antenna is peaked for 432.1 MHz. At this frequency,
this antenna is getting very practical and easy to build. Driven element
dimensions are L = 13.0" and H = 3/8" Elements are 1/8" diameter.
|432 MHz||Reflector||Driven||Dir 1||Dir 2||Dir 3||Dir 4||Dir 5||Dir 6||Dir 7||Dir 8||Dir 9|
902/903 MHz. This was the first antenna I built using the antenna to control the driven element impedance. The 2 1/2' length has proven practical, so I haven't built any other versions. Driven element dimensions are L = 5.7" and H = 1/2" Elements are 1/8" diameter.
|902/903 MHz||Reflector||Driven||Director 1||Director 2||Director 3||Director 4||Director 5||Director 6||Director 7||Director 8|
* See diagram above for details. 9.10" Total length.
UPDATE: My antenna was measured at the CSVHF Society 2000 Meeting in Winnipeg, Manitoba, Canada by Kent Britian himself. It made a pretty good account of itself, and actually would have won an award if they actually would have had some for antennas this year!!
Here is a picture of the constructed antenna, with a close up of Kent's handwriting (fuzzy but readable-- cheap webcam photo): The measured gain was 12.6 dBd, not bad for a $10 antenna constructed in about an hour.
1296 MHz. This antenna is the veteran of several "Grid Peditions"
but I have yet to actually measure the gain. Dimensions must be followed
with great care. The driven element is small enough to allow 0.141 semi-rigid
coax to be used instead of RG-58. Silicon Bronze welding rod was used for
the elements but any material can be used. Driven element dimensions are
L = 4.0" and H = 1/2" Elements are 1/8" diameter.
|1296 MHz||Reflector||Driven||Dir 1||Dir 2||Dir 3||Dir 4||Dir 5||Dir 6||Dir 7||Dir 8|