A Quick and Simple 2 Meter Ground Plane
Project! (With a handy calculator you can
download!)
If you are just getting experience in building antennas or you
are an old pro, here is a simple and fun project! This antenna is
perfect for those hams living in the primary coverage area of the repeater
for 2 meter use. This antenna is nothing more than the old standby
"Droopy Groundplane" and can be used on any band where it's physical size
does not pose a problem. Remember that the vertical radiator is 1/4
wavelength long at your operating frequency.
It has no gain but
makes an excellent small antenna that can be mounted just about anywhere
and with a little planning, can be used mobile on a short mast from the
bumper!! Adding a small attachment loop at the tip of the radiator will
enable it to be suspended from above for inside use.
Build it! (See drawing
below)
The vertical
element and radials can be made of #12 copper wire or welding rods, coat
hanger, etc. The vertical radiator (A) should be soldered to the center
connector of the SO239. The four base radials (B & C) and (D & E) can be
soldered or bolted to the SO239 mounting holes using 4-40 hardware.
The four base radials then should be bent
downward to a 45 degree angle.
The antenna can be
mounted by clamping the PL259 to a mast or even passing the coax through a
3/4 ID PVC pipe and compression clamping the PL259. Either way let your
creativity work for you. If you plan on mounting it outside, apply
RTV or sealant around the center pin and PL259, and
TAPE
WELL, to
keep water out of the coax.
Make each radial a 1/4 wave of your desired xmit frequency.
Sometimes it helps to add a little extra length to the radials and
radiator. This will give you some adjusting room when you adjust the
SWR. (If adjustment is needed, clip all radials equally about 1/8 inch
at a time while checking SWR, USING LOW POWER). Center the lowest swr
on your transmit operating frequency.
Example
Calculation: Freq (mhz)
146 A
(inches) 19 5/16 (Note "A"
length is to the SO-239 insulator but not
critical) B THRU E (INCHES) 20
3/16 LENGTHS FROM FORMULA ( 234/FREQ MHZ) + 5 %
LONGER FOR RADIALS
TRY ONE ON 440 or other
bands USING SAME FORMULA AND CONSTRUCTION TECHNIQUES! ENJOY AND EXPERIMENT! DON'T TRY IT ON 75 METERS
MOBILE......IT' A LITTLE LONG FOR MOST BRIDGES, OVERPASSES, POWER LINES
ETC!!!!
Download the calculator to design
your 1/4 wave ground plane, plus a bonus!
This calculator not only designs a ground plane but also an
Inverted V and a dipole! Courtesy of and designed
by N2IMF Joseph R
Mielko
Screen shot below of calculator - Non
working. You can download the program below or here.
