Quote:
Originally Posted by Winnipesaukee
I thought as long as an antenna had a certain amount of resistance (I think most VHF antennas are 50 ohms), it would not damage anything.
..And it would operate efficiently if the length of the antenna "matched" the length of the wave?
Airwaves? Where are you???
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The correct term here is impedance, not resistance. A huge difference when disscussing AC components versus DC.
In order to be a match (show the correct impedance of 50 ohms) the antenna's "electrical" length must match that of the output of the radio. That output is determined by frequency. (that is why you usually see antennas rated as 1/4 wave, 1/2 wave or full wave in design)
A CB antenna is electrically matched to show 50 ohms when it's length matches a certain fraction of the wavelength of 27 mhz. A VHF marine antenna therefore shows a 50 ohm impedance in the 156 mhz range.
Connecting a VHF radio to a cb antenna will cause no harm while it's receiving, although receive range will be greatly diminished. When you transmit however the impedance mismatch will cause much of the RF energy to be reflected back into the final output stage of the transmitter, While most modern transmitters have protection that will shunt this or decrease output power, continual usage will most likely result in damage.