Random Wire Antenna

A "Random Wire" antenna is an end-fed antenna that is operated against ground or an artificial ground system - much like a vertical antenna. The "Random Wire" must normally be coupled to the transmitter by an ATU (except if it happens to be in resonance on some amateur band).

A popular length is 7m. This does not provide excessive impedances for the ATU to tune out for bands between 80 and 10m.

Jack Clarke VE3EED adds that for optimum performance, "random length" antennas should not be multiples of half wavelengths in the intended bands. The following table reproduced with permission from his website details half wave lengths that should be avoided.

Further calculations by Jack led him to produce the following list of "preferred" list of antenna lengths, to avoid half wavelengths and their multiples (measurements in feet):

29 35.5  41  58  71  84  107  119  148  203  347  407  423