Table Top 145 MHz Power Amplifier Project

This project was started to enable the author to assist in the teaching of practical implementation of RF techniques for Degree level students . By using the software that the student's use it was possible to use all the practical knowledge gained from 30 years as a Radio Amateur together with the 10 years working in commercial radio manufacture & test .

The project brief was written such that any student doing a B Eng or M Eng Degree could construct each of the modules independantly and test it accordingly. The collection of tested modules could then be assembled into the final Amplifier unit .

Specification for a VHF power amplifier for radio service

• The amplifier is designed to be inserted between a transceiver & aerial to enhance the range of the transceiver . ( Po required 150 Watts < )
• Provision for low noise RF pre amp of equivalent gain in receive path
• The nominal drive level is around 10 - 12 Watts the range of frequencies is 140 - 175 MHz ( must cover 144 - 146 MHz )
• Frequency response to be +/- 0.25 dB across band of operation.
• All modes ( FM / SSB ) must be catered for .
• The unit to be mains powered & capable of unattended operation .
• The amplifier must be capable of running Full power for at least 15 mins on with a 50% duty cycle . All spurious signals to be at least -60dBc both via the O/p cable & leakage from the amplifier .
• Full protection of the unit is required against High VSWR , Over temperature ( with indication of fault conditions ) Micro processor control is permissible ( subject to EMC requirements)
• The unit should be reasonably compact .

The Modules used are as follows :-

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This page last updated 10 July 2008