Motivation & Constraints For The Project

Let me first say that I believe there are lots of great reasons to build a HB amplifier. These are simply mine.

This is a hard one to explain; at least to  people outside of ham radio. For me">

Motivation & Constraints For The Project

Let me first say that I believe there are lots of great reasons to build a HB amplifier. These are simply mine.

This is a hard one to explain; at least to  people outside of ham radio. For me, it was not to save money over a commercial amplifier. It sure isn't to save time! I wanted to have the satisfaction of building and operating a homebrew  amplifier. I wanted to know why every component was in there and how its value was selected. I also wanted to build it with a lot of salvaged parts. I wanted it to look "OK", but rivaling the appearance of commercial equipment would not be a goal for this project. As a matter of fact, to most people it will not be attractive at all! And that's ok. Using "parts on hand" and salvaged parts means buying into it taking more space and a less than optimum packaging arrangement.

Here is the short list of constraints I started with:

  1. A single tube amplifier
  2. Use an Eimac 4-400A Power Tetrode
  3. Use 110 volts for the power supply (instead of 220)
  4. Avoid using a band switch by including a variable inductor in the output network
  5. Have front panel controls for setting the operating point of the amplifier tube
  6. Use a common cathode configuration ( drive the grid of the tube )

But Why?

  1. Simplicity and cost
  2. I already had it!
  3. Didn't want to run a 220 line to the operating position & wasn't running real high power anyway (with this tube)
  4. Good band switches are expensive & thought a variable coil would simplify wiring issues
  5. I wanted a lot of flexibility in how I biased the tube - different classes of operation
  6. I was originally set to build a grounded grid amplifier. The more I looked into it the more I was drawn to a grounded cathode design. Didn't want the amplifier signal to  flow through the driver. And, I didn't like the low gain of the common grid circuits.

Well, there it is. As best I can remember the beginning anyway. Were these good reasons? Well, as they say, "it seemed like the thing to do at the time".       ....  ..