To set up the MF/HF Transceiver for a TELEX call, the operator must?

To establish a TELEX call using an MF/HF transceiver, selecting the appropriate mode is crucial for successful communication. The correct answer highlights that the operator should select F1B mode or J2B mode based on the capabilities of the equipment being used.

F1B mode is a two-frequency shift keying mode that is specifically designed for facsimile communication, which allows for the transmission of text and data. On the other hand, J2B mode is another variant that may be supported by some equipment for direct teletypewriter communication.

Choosing between these modes depends on the equipment's specifications and what it supports, ensuring that the setup aligns with the operational requirements. In a practical scenario, using the right mode is necessary to ensure that the transmission is recognized and processed appropriately by the receiving equipment. Hence, the operator must be familiar with their equipment capabilities to choose correctly between F1B and J2B modes.

Other options do not apply as relevant for TELEX calls. J3E mode is associated with single sideband audio transmission, which is not compatible with the need for text-based communication in a TELEX context. Therefore, understanding the equipment's operational mode options ensures effective communication using the MF/HF transceiver.