Abstract: The present invention relates to an antenna for use on a motor vehicle, particularly for cellular radio communication. The antenna comprises an elongate conductor applied to the surface of a vehicle window, the length of the antenna elongate conductor being a minor portion of the length of any peripheral side or edge of the vehicle window. A ground plane is provided along the top edge of the vehicle window, and the top end of the conductor antenna is grounded by virtue of its close proximity to the ground plane.

Abstract: The present invention provides within three particular aspects thereof an isolating and matching device operable to enable an electrically heatable window of a motor vehicle to be used as an efficient VHF communications aerial or antenna; wherein isolating and matching circuitry is provided for Series VHF Matching, Shunt VHF Matching and Split Passband Matching of an electrically heatable window heating element to an aerial input impedance of an aerial feeder circuit of a radio frequency receiver or transmit/receive device.

Abstract: The present invention provides within three particular aspects thereof an isolating and matching device operable to enable an electrically heatable window of a motor vehicle to be used as an efficient VHF communications aerial or antenna; wherein isolating and matching circuitry is provided for Series VHF Matching, Shunt VHF Matching and Split Passband Matching of an electrically heatable window heating element to an aerial input impedance of an aerial feeder circuit of a radio frequency receiver or transmit/receive device.

Abstract: The present invention provides within three particular aspects thereof an isolating and matching device operable to enable an electrically heatable window of a motor vehicle to be used as an efficient VHF communications aerial or antenna; wherein isolating and matching circuitry is provided for Series VHF Matching, Shunt VHF Matching and Split Passband Matching of an electrically heatable window heating element to an aerial input impedance of an aerial feeder circuit of a radio frequency receiver or transmit/receive device.

Abstract: The present invention provides diversity reception to effectively compensate for signal reception fading without using separate antenna structures and while using the heating element antenna of an electrically heated window of a motor vehicle. Such is accomplished by providing common (unbalanced) and balanced signal separation configurations and signal selection circuitry between the heating element antenna and the VHF aerial input terminal of a vehicle radio receiver, wherein the signal selection circuitry selectively connects the signal outputs of the common and balanced signal separation configurations to the VHF aerial input in dependence on monitored characteristics of the radio signals produced at these outputs and received by the vehicle radio receiver.

Abstract: The present invention provides within three particular aspects thereof an isolating and matching device operable to enable an electrically heatable window of a motor vehicle to be used as an efficient VHF communications aerial or antenna; wherein isolating and matching circuitry is provided for Series VHF Matching, Shunt VHF Matching and Split Passband Matching of an electrically heatable window heating element to an aerial input impedance of an aerial feeder circuit of a radio frequency receiver or transmit/receiver device.

Abstract: A relay system for relaying hyperbolic navigation signal information received at a mobile. The mobile has a simple relay transmitter and receives signals which are radiated from different navigation transmitters in turn on a single frequency f.sub.rf. The received signals are heterodyned to a single audio frequency f by mixing with a locally-generated or transmitted signal f.sub.o. Phase errors are minimized by transmitting the information as phase changes of the single frequency f signal in a single transmission channel.