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A Quick and Simple 2 Meter Ground Plane
Project!
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!!!!
Thousands
of Electronic Parts here!


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