Transmitter Theory

Question File Number 19



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The Fundamentals of Transmitters

The basics of radio transmitters have been treated in Transmitter Block Diagrams TX Blocks.

The characteristics of the various modulation methods are covered in Signals.

The Power Rating of a SSB linear amplifier

A power amplifier for SSB operation is required to be linear. This means that the waveform of the output signal must be a replica of the input waveform in all ways except amplitude - the output must be an amplified version of the input! The maximum power output before severe distortion takes place is the limit of successful linear amplifier operation.

The power output at the maximum level is the usual rating given for a linear amplifier. This is known as the Peak Envelope Power, PEP.

The PEP is by definition, the average power output during one RF cycle at the crest of the modulating envelope. Definition

The PEP rating and measurement are also sometimes used for amplifiers for other modes.

The RF output power from an amplifier is less than the total DC input power and signal input power to the amplifier. The difference is energy loss and appears as heat. Cooling facilities - fans etc. - are sometimes found on solid-state power amplifiers for protection from over-heating.



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Compiled Sun Nov 28 2010 at 8:41:44pm


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