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 SIMPLE 2 METER GROUND PLANE PROJECT
Posted byadminshc on Friday, April 20 @ 13:04:29 MYT
Contributed by adminshc
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
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.
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 transmitting 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
UPDATE
Here is an example of a novel way to mount the ground plane on a length
of PVC!
Suggested by Malcolm, KC0YNR:
I built the QUICK AND SIMPLE
2 METER GROUND PLANE PROJECT out of #12 copper wire and an SO239.
I drilled a hole in a 1" PVC cap large enough to fit an SO239 socket
into, and used 1" PVC pipe, 12ft long total to mount it on. Screwing the PL259 on from the bottom of the PVC cap held the SO239
in place nicely. (Also see drawing below)
Works like a champ. With a little trimming I got SWR at 1:1 on the entire 2M band. No gain but got good reports, and I'm hitting the repeater 5miles away at 5 watts with a good signal. Next version will
be a little more sturdy. 2 of the groundplane wires broke off and I still
got good signal to the repeater.
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