05604506 is referenced by 41 patents and cites 19 patents.

A dual frequency vertical antenna for radiating a first and a second airwave signal in response to a first and a second conducted signal, the first airwave signal having a first frequency and the second airwave signal having a second frequency lower than one-half the first frequency. The antenna includes a horizontal base member and a vertical mast, including a coaxially disposed rod, projecting upward from the base member to a masthead. For feeding the conducted signals, a lower mast extension projecting downward from the base member and a tuning sleeve projecting either upward or downward from the base member are tuned to 1/4 wavelength at the first frequency and a single coaxial cable is connected between the base member and a feedpoint on the rod. The first airwave signal radiates from a dipole formed of an 1/4 wavelength upper rod extension extending upward from the masthead and a concentric 1/4 wavelength upper sleeve external to the mast projecting downward from the masthead. The mast is 1/4 wavelength at the second frequency for radiating the second airwave signal from a dipole formed of the mast and the base member.

Title
Dual frequency vertical antenna
Application Number
8/354617
Publication Number
5604506
Application Date
December 13, 1994
Publication Date
February 18, 1997
Inventor
Eric B Rodal
Cupertino
CA, US
Agent
David R Gildea
Assignee
Trimble Navigation
CA, US
IPC
H01Q 9/40
View Original Source