A communications system comprising: a high-power signal cable coupled to a signal amplifier, the high-power signal cable to convey a transmission signal produced by the signal amplifier; a radio frequency circuit (215, 216, 205, 210, 211) coupled to the high-power signal cable, the radio frequency circuit configured to transmit and receive signals, the radio frequency circuit comprising: a plurality of antennas (210, 211), a passive network having a plurality of output ports and a plurality of input ports, each output port coupled to an antenna of the plurality of antennas, the passive network configured to provide a signal at an input port to an output port, and a plurality of switches (215, 216) coupled to the high-power signal cable, each switch coupled to an input port in the plurality of input ports, the plurality of switches to selectively couple the transmission signal conveyed by the high-power signal cable to the plurality of input ports based on a control signal; and the communications system further comprising: a control unit coupled to the plurality of switches, the control unit configured to produce the control signal based on a specified coupling of the high-power signal cable to the plurality of antennas, wherein the plurality of switches selectively couples the transmission signal to a single input port or to all input ports in the plurality of input ports, wherein when the plurality of switches couple the transmission signal to all input ports in the plurality of input ports, the transmission signal is transmitted by all the antennas in the plurality of antennas and has an omnidirectional transmission pattern. a high-power signal cable coupled to a signal amplifier, the high-power signal cable to convey a transmission signal produced by the signal amplifier; a radio frequency circuit (215, 216, 205, 210, 211) coupled to the high-power signal cable, the radio frequency circuit configured to transmit and receive signals, the radio frequency circuit comprising: a plurality of antennas (210, 211), a passive network having a plurality of output ports and a plurality of input ports, each output port coupled to an antenna of the plurality of antennas, the passive network configured to provide a signal at an input port to an output port, and a plurality of switches (215, 216) coupled to the high-power signal cable, each switch coupled to an input port in the plurality of input ports, the plurality of switches to selectively couple the transmission signal conveyed by the high-power signal cable to the plurality of input ports based on a control signal; and the communications system further comprising: a control unit coupled to the plurality of switches, the control unit configured to produce the control signal based on a specified coupling of the high-power signal cable to the plurality of antennas, wherein the plurality of switches selectively couples the transmission signal to a single input port or to all input ports in the plurality of input ports, wherein when the plurality of switches couple the transmission signal to all input ports in the plurality of input ports, the transmission signal is transmitted by all the antennas in the plurality of antennas and has an omnidirectional transmission pattern. a plurality of antennas (210, 211), a passive network having a plurality of output ports and a plurality of input ports, each output port coupled to an antenna of the plurality of antennas, the passive network configured to provide a signal at an input port to an output port, and a plurality of switches (215, 216) coupled to the high-power signal cable, each switch coupled to an input port in the plurality of input ports, the plurality of switches to selectively couple the transmission signal conveyed by the high-power signal cable to the plurality of input ports based on a control signal; and the communications system further comprising: a control unit coupled to the plurality of switches, the control unit configured to produce the control signal based on a specified coupling of the high-power signal cable to the plurality of antennas, wherein the plurality of switches selectively couples the transmission signal to a single input port or to all input ports in the plurality of input ports, wherein when the plurality of switches couple the transmission signal to all input ports in the plurality of input ports, the transmission signal is transmitted by all the antennas in the plurality of antennas and has an omnidirectional transmission pattern. a control unit coupled to the plurality of switches, the control unit configured to produce the control signal based on a specified coupling of the high-power signal cable to the plurality of antennas, wherein the plurality of switches selectively couples the transmission signal to a single input port or to all input ports in the plurality of input ports, wherein when the plurality of switches couple the transmission signal to all input ports in the plurality of input ports, the transmission signal is transmitted by all the antennas in the plurality of antennas and has an omnidirectional transmission pattern.