SPECIAL CIRCUITS

During certain communications operations, you may be required to activate and operate special circuits. Some of the most common special circuits are discussed next.

UHF AUTOCAT/SATCAT/MIDDLEMAN RELAY CIRCUITS

Shipboard HERO conditions and emission control (EMCON) restrictions often prohibit transmission of RF below 30 MHz.

To provide an uninterrupted flow of essential communications without violating HERO and EMCON restrictions, AUTOCAT, SATCAT, and MIDDLEMAN were developed. With these techniques, the range of tactical UHF circuits (voice or teleprinter) can be extended by relay of AM UHF transmissions via HF or satellite. AUTOCAT accomplishes this using a ship; whereas SATCAT uses an airborne platform for automatically relaying UHF transmissions. MIDDLEMAN requires an operator to copy the messages with subsequent manual retransmission.

The three techniques just discussed use three different types of circuit for reception and relay of UHF transmissions. These circuits are as follows:

A voice circuit where some units send and receive on one frequency, and other units send and receive on any other frequency;

A voice circuit where all units transmit on one frequency and receive on another frequency; and

A RATT circuit where all units transmit on one frequency and receive on another frequency.

FLEET FLASH NET

The Fleet Flash Net (FFN) is composed of senior operational staffs and other designated subscribers. The purpose of the FFN is to distribute high-precedence or highly sensitive traffic among subscribers. A receipt on the net constitutes firm delivery, and the message need not be retransmitted over other circuits to receipting stations. The FFN is explained in more detail in Mission Communications, NTP 11.

ANTENNA SYSTEMS

Operation of communication equipment over the entire range of the RF spectrum requires many types of atennnas. You will need to know the basic type of antennas available to you operationally, their characteristics, and their uses, Very often, you, the operator, can mean the difference between efficient and inefficient communications. You will have a choice of many antennas and must select the one most suitable for the task at hand. Your operational training will acquaint you with the knowledge necessary to properly use the antennas at your disposal, However, your operational training WILL NOT acquaint you with the WHY of antennas, in other words, basic antenna theory. The following topics are intended to familiarize you with basic antenna terminology, definitions, and characteristics.