^ >

^ > 75/120 = 0.625 meters

^

^ Or, to put that in American, L in feet = 468/MHz.

I did use Amurican. Amurica is part of the international community and the

meter is the international standard measurement of length. Besides, it's much

easier to measure 0.625 meters on a bilingual yardstick, or meter stick, then

it is to measure 2.05 feet. It's also easier then doing the additional math

that you suggest.

^ 468/120 = 3.9 feet. This is, of course, the length of the entire dipole.

^ For each leg, you'd use 234/120 = 1.95 feet, or simply divide the 3.9 by 2.

Note that the formula I gave produces the length of each leg. The

relationship is that electromagnetic energy travels at three hundred million

meters per second (300,000,000 m/s) and a megahertz is one million cycles per

second (1,000,000 1/s). To find meters (the length of one cycle) divide

3,000,000 by the frequency in MHz:

300,000,000 m/s

-------------------

120,000,000 1/s

The seconds divide out and 'm/1' becomes just 'm', and the resulting value is

the length of one wave in meters. Note that the 000,000 also divides out so

the math can be abbreviated as 300/120. To find a half or quarter wavelength

it is generally easier to first divide the 300 by two (150) or four (75),

which are easily remembered, then it is to perform the second division on the

resulting value.

To be more precise the resulting value for a quarter wavelength would be

multiplied by the velocity factor of the wire being used, but since these

antennas are normally intended for receiving a wide frequency range such

precision is generally wasted effort.

Frank