Editors
note: This antenna project and article was originally posted on the
UKSMG Web Site, (The UK 6 Meter Group), in Metric measurements and
is presented here for your enjoyment in U.S measurements. Full credit
goes to the author of the article, MIKE, G3JVL. Only minor editing changes were
made for clarity of measurements ( Metric conversion to feet and
inches) and
wording......N4UJW ___________________________________________________
The G3JVL 6 Meter ground plane vertical is a compact antenna
that is ideal for portable operations. If needed, it can be disassembled
into a very small bundle no longer than the longest
element.
Although a little engineering work is required, it is well
within the abilities of the home workshop and all you newly licensed
amateurs or 6 Meter buffs!
The vertical itself is constructed out
of four overlapping sections of aluminum tube whose sizes are given in the
diagram below. The four tubes are meant to telescope, so wall thickness
should be chosen to achieve this. In practice, 16swg might be OK but
18swg will easily fit. The lengths can be held in place by three
stainless steel self-tapping screws or hose clamps.
The vertical is
bottom-loaded with a coil wound on an insulated form (nylon or similar
material - it is not too critical at 50MHz). - the form is about 5 inches
long with the top 3/4 inch turned so it can be inserted into the bottom
section of the vertical. The loading coil consists of ten turns of 16swg
diameter coated or insulated copper wire with one end connected to the
bottom section of the vertical with a machine screw and the other end
connected to the ground plate. An adjustable tap at 5-turns is connected
to the input PL-259 socket. Tap can be soldered or permanently attached in
place after VSRW adjustment is
final.
Base Details
Below:
The construction of the 6m vertical
antenna The four ground plane elements
are Constructed from 49.2 inch long, (3/8") diameter aluminum tube.
These are mounted to the base plate by the use of eight stainless steel
machine screws. This arrangement allows easy disassembly if
needed.
The vertical itself is supported by a piece of 14 inch by 2
inch aluminum plate about 1/8 to 3/16 inch thick bent into a 90 degree
angle on each end forming a... |______|... shape as viewed from the side
and layed down. The bottom section of the vertical is insulated by a
turned piece of nylon or similar tubing. If you do not have access to a
lathe, any other insulating arrangement should suffice so long as it is
robust and can withstand wind loading on the mount.
The overall
length of the vertical is about 13 feet 6 inches including the loading
coil. The top section should be adjusted to set the center frequency.
If the VSWR at resonance is not close to 1:1 then alter the position of
the tap on the loading coil (remember, changing this will alter the
resonance of the antenna!).
Once completed give the whole assembly
several coats of varnish to keep out the weather.
