Abstract: A multiplexer circuit adapted to receive signals comprises two filter circuits. The first filter circuit presents a high impedance to signals outside a first frequency range and the second circuit presents a high impedance to signals outside a second frequency range. Isolation matching circuits enable transmission and reception of one of the signals in the first or second frequency ranges without degradation or interference with the other range. An embodiment allows transmission and reception of satellite Orbcomm frequencies over a standard AM/FM antenna without effect on the AM/FM signal.

Abstract: An AM/FM/WB/CB/cellular telephone antenna includes a first frequency self-resonant circuit at a position above the lower end of the antenna such that the electrical length of the lower section of the antenna is equivalent to one-quarter wavelength for a frequency in the FM frequency range and a second frequency self-resonant circuit disposed below the first frequency self-resonant circuit. The first self-resonant circuit presents a high impedance in the FM frequency band and the second self-resonant circuit presents a high impedance in the cellular frequency range. The entire length of the antenna is equivalent to one-quarter wavelength in a frequency in the CB frequency band. The antenna wire is wound around a fiberglass core, and the FM self-resonant circuit is formed by a tightly wound, coiled section of the wire together with a thin-walled brass tube extending over the core in the area of the tightly wound section.