Transmit / Receive switching

Transmit / Receive switching

• Most frequently, an amateur uses the same antenna to transmit and receive on a given band. The transceiver generally provides a single antenna connector on its back panel. An internal system connects the antenna to the receiver or transmitter.
• In a typical contact on a single frequency, each party talks one at a time, while the other listens.
• While you are in receive mode:
  • The antenna must be connected to the receiver section of the transceiver.
  • The transmitter remains on standby.
• When you switch to transmit mode:
  • The antenna must be connected to the transmitter section of the transceiver.
  • The receiver is deactivated.
    • [ To avoid the wailing that audio feedback (new tab or window) would produce. ]
    • [ To protect the sensitive receiver from the comparatively very strong signal about to be transmitted. ]

• In a transceiver, a switching system must:
  • Connect the antenna to the active unit.
  • Disable the unit not being used.
• An electromechanical relay (new tab or window) can perform these functions:
  • When switched on, an electromagnet (a coil) exerts a pulling force to move electrical contacts.
  • [ For an analogy, the relay is to electricity what the railroad switch (new tab or window) is to the railway industry. ]

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The following application illustrates how power is applied to one section or the other, while also switching the antenna to the correct unit.

Transmit/Receive switching

Press a button to alternate
between transmit and receive …

Transmit Receive Power off

[ Whether the transmitter and receiver are separate or combined within the same cabinet, the concept of transmit/receive switching must be implemented. ]

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