Could you cut or lenghten a 2 meter ham (144 to 148 Mhz) broadcast antenna to make it broadcast FM (88 to 108 Mhz)?
If so is there an equation for this?
2006-08-11 04:52:01 · 3 answers · asked by Anonymous in Consumer Electronics ➔ Other - Electronics
A quarter wave ham antenna at 146 MHz is about 1/2 of a meter. A quarter wave FM antenna at 98 MHz is about 3/4 of a meter. The 2 meter ham band is only 2 MHz wide and one antenna will cover that. The FM band is 20 MHz wide, so you need to know what frequency you want and adjust the length accordingly.
There is another problem, however. FM antennas (as well as television antennas) are 75 ohm impedance and ham antennas are 50 ohm impedance. You can't just use one for the other and have the best performance.
2006-08-11 06:59:02 · answer #1 · answered by Anonymous · 0⤊ 1⤋
Yes.....I forget the exact formula but it is derived from the speed of light times the duration of one cycle (1/f).The most common antennas are 1/4 wave but half wave or full wave is best especially for amateur frequencies. Remember that f=1/t
f is frequency
t is time
When calculating watch your units very carefully and you will end with an answer in inches or whatever unit of length you are using.
2006-08-11 13:36:52 · answer #2 · answered by Mike M 4 · 0⤊ 0⤋
If it is a whip antenna then you can increase its length so that its resonant frequency falls within the f.m. broadcast band.
(Amateur bands are not referred to as "broadcast.")
You can find antenna design information on the net.
However, if your antenna has a loading coil the extra length will have to be determined by trial and error.
2006-08-11 12:58:06 · answer #3 · answered by dmb06851 7 · 0⤊ 0⤋