5. Principle of Operation
The internal FM exciter found inside FM transmitter enclosures accepts analog, digital or MPX audio
signals and modulates them onto an FM carrier. The analog signal can be either mono or stereo (both
included as standard), while the digital inputs are accepted on AES3, S/PDIF optical (Toslink), or S/PDIF
coaxial inputs. Also included on the Interface circuit board are amplifier stages to increase the modulated
level from a few dBm up to approximately 1 Watt.
The RF power amplifier stages are designed to take a modulated FM carrier from the Exciter/Interface
board and amplify the carrier to the specified power level. The power amplifier feeds the antenna through
an inline wattmeter and transmission line. For broadcast and over-the-air amplifier systems, the pattern
of the antenna then dictates the range and coverage area.
The amplification is accomplished by one or many amplifier pallets internal to the power amplifier system.
If there is more than one amplifier pallet stage, then the first pallet acts as a driver feeding Intermediate
Power Amplifiers (IPAs) and/or final stage pallets. If multiple final pallets are required, then a splitter and
combiner are also required before and after the final stages.
Technalogix manufactures FM amplifiers and transmission systems suitable for 87.5 to 108.0 MHz.
Custom frequencies are available upon request if you require carriers outside this range, including audio
for VHF applications and other unique requirements.
The RF amplifiers utilize readily available RF components wherever possible, thus enhancing the
serviceability of the equipment. The amplifier modules are stable for high reliability and long service life
and feature ultra linear amplification and RF output filtering.
The Block Diagram is included in this manual to illustrate the specific component flow of the RF amplifier
system and to provide specific configuration and model information.
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