CENTER OF FREQUENCY CUTTING CHART

1/4 WAVE AMATEUR RADIO

50.500MHz     55.60" RADIATOR     58.38" RADIALS

52.500MHz     53.49" RADIATOR     56.16" RADIALS

146.00MHz     19.23" RADIATOR     20.19" RADIALS

222.00MHz     12.65" RADIATOR     13.28" RADIALS

427.00MHz       6.58" RADIATOR       6.90" RADIALS

432.00MHz       6.50" RADIATOR       6.83" RADIALS

437.00MHz       6.43" RADIATOR       6.75" RADIALS

442.00MHz      6.35" RADIATOR        6.67" RADIALS

447.00MHz      6.28" RADIATOR        6.60" RADIALS

One of the simplest antennas you can build is a quarter wave ground plane. It is small in size and is inexpensive. The only part you will need to buy is a SO-239 panel mount connector. You can use an old wire clothes hanger for the radiator and radials. You will need to use your soldering iron or gun to attach the radiator to the center post of the SO-239. File any paint or coating from the radiator wire before soldering it. If you can find a short copper tube to help secure the radiator to the SO-239, your antenna will stand up to high winds.

The radials may be soldered or attached with screws. Screws are the easier method if you take the time to over lap them. The radials should be bent to an angle of 45 degrees for 52 ohm base impedance. If the radials are perpendicular to the radiator, the base impedance is approx. 36 ohms. Radials parallel to the radiator have an impedance of approx 75 ohms.

Apply a small amount of sealant around the center pin to prevent water from entering the connector. Attach your coax to the bottom of the SO-239, then use a  hose clamp to attach the SO-239 to your pipe or tower mount.

A good friend Jim N5VGQ asked me to also mention that you can make a small loop in the top of the radiator and tie a string and hang it from the wall using only 2 radials for a bad weather antenna.