Sunday, January 30, 2022

A 500 Watt HF Power Amplifier: Part1 - Overview

 I am building a 500 watt linear amplifier.  This is my first big ham radio hardware project.  The Stationmaster software that I use to run my station is a reasonably large software project and it is getting bigger.  You can find the details here.

I am using two sources for the design and building of this amplifier.  My primary source is Jeff Anderson (K6JCA) and his excellent blog and guidance.  The second source is the Micro Semi App Note 1819 that Jeff references and all the references in the app note.  I have also spent time Googling for things that I don't know, which is a lot.

What I am doing here is based on Jeff Anderson's work.  It will be hard to follow my work without knowing his which you can find here.

I am using Jeff's specifications and protection scheme.  At some point I will copy them for the sake of completeness, but for now, they can be referenced in his blog.  

I am taking a simulation approach to the design to complement Jeff's experimental approach and I hope to be able to duplicate his results in the simulator.  I started by using Mac Spice but it did not do a great job of simulating transformers and transmission lines.  Jeff, K6JCA, recommended LT Spice which has worked well for the most part.

Below is the block diagram of the design as it stands today.  I put the the supervisory circuits with the power sub-assembly and used a different layout than the Micro Semi board.  I will discuss the layout details in the power sub-assembly section.  I was hoping to package the directional coupler and the low pass filter together but I did not find a way to fit that combination in a 3U high 19" enclosure.  They are packaged separately.  I am planning to control the low pass filter band selection with the band switch of my Ten Tec Omni D radio.  So the chances of selecting the wrong band and filter combination is eliminated (minimized?).  I have dropped the directional coupler between the power sub assembly and low pass filters.    

A 500 Watt HF Power Amplifier: Part 1 - Overview

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