[AMRadio] antenna tuners


Gary Schafer garyschafer at comcast.net
Thu Apr 20 22:12:15 EDT 2006


This is another tidbit to keep in mind for those that still may think that
an antenna has to be resonant to give 1:1 swr. 

A dipole antenna rarely is 50 ohms at resonance. It is very dependent on
height above ground as to what impedance it presents at the feed point. It
can range anywhere from below 30 ohms to above 70 ohms.

So if you cut your antenna so that you have 1:1 swr at the transmitter end
of the coax, the antenna is probably not tuned to resonance! You have
detuned the antenna to change its impedance that the coax sees. 

Only rarely does a resonant antenna turn out to be 50 ohms.

73
Gary  K4FMX





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