Grid Driven Tetrode Linear RF Amplifier building using the 4cx250

I enjoy building and operating RF Amplifiers. The 4CX250 is one great tube to use in your amplifier projects. Many popular HF Amplifiers feature grid driven tetrodes. This paper shows circuit information I've referenced many times through the years. It's mostly a way to show you a method of stable drive application and bias through a tuned input. Since the bias and screen power supplies are often magic to the new builder, I've also included the simple and solid circuits I like.

*Note. This is an "older technology" circuit diagram. I no longer use resistors or capacitors paralleled with the current generation of silicon diodes. I would also consider adding a shunt voltage regulator to the screen supply, which would improve the amplifiers linearity.

Proper cautions apply when working around RF and High Voltage please. The circuit features a single 4cx250 circuit with band swtiched tuned inputs for the original 80-10 bands. Often found at bargain prices, the 4cx250 tetrode is "a real bang for the buck". This is a zip file package which contains the circuit diagram in gif and Adobe PDF file formats.


We/I get a lot of Email from visitors who drop into these file down load description pages via a web search "engine" (like Google). Vistors are not able to locate the file download icon for that specific description page. There is a simple way to find the file download icons on the main sonic web page...

First and best: Use the menu icon just below to the main sonic page.

Second: Back space out the page your now looking at in your browser location line. As an example, using the description page. Remove the last portion of the web location with the keyboard back space key to read then press your Enter Key to reload the main sonic page "just in front" which would probably has the inforamation you're looking for. This works on most of the current browsers at most web sites.

Third: You can always contact me using the Email Icon below. I'll try to get a back to you asap with a practical answer.

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