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How to Use Relays at VHF Frequencies

Relays perform switching functions quickly from remote locations. Two wires connected to the coil of the relay operate an electromagnet that pulls contacts together for a multitude of purposes. For VHF signals that travel best over coaxial cable, a coaxial relay will keep the connections shielded within a metal case. You can buy a coaxial relay with BNC, F, N, VHF or other types of connections to suit your needs. Coils can operate with AC or DC control circuits. You need considerable technical experience to select and connect coaxial relays for your application, and possibly the ability to solder.

Things You'll Need

Coaxial relay
Connectors to suit the application
Coaxial cable
Wire
Electronic technician hand tools
Soldering equipment

Instructions

- 1
  Select a coaxial relay suitable for your application. Consider coaxial connections, power of the signal in watts or amps, voltage and current ratings of the coil and environmental conditions. Also consider physical dimensions and mounting, such as held in place by hardware or soldered to a circuit board. Several options are available.
- 2
  Install the relay in a suitable location to reach the signalcables to be switched and the control wiring. For outdoor operation, consider a weatherproof housing.
- 3
  Connect the signal to be switched to the common (C) terminal or the relay. Connect the two optional switch cables to the normally open (NO) and normally closed (NC) terminals on the relay. When the relay is idle, the connection goes from the C to the NC terminals. When energized, the signal goes to the NO terminal.
- 4
  Connect two wires from the control circuit to the coil terminals of the relay. You can use one wire and ground in many applications. Apply control voltage to the coil and check to see that your signal switches as desired.

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