Homebrew 3CX3000A7 Amplifier

Note: I have many images of the build in progress- It will take some time for me to get this page into shape=

I had been looking for a rugged HF linear amplifier with plenty of headroom. I had a Yeasu 2100F, Heathkit Warrior, and Henry 2K3. I just wasn’t getting the dynamic range out of these amps. Here’s my build along the way. It’s still not complete but is on the air. I ordered a complete set of control and instrumentation boards from WD7S- all the boards are now completed, hope finish the amp in a month or two.

I started with a prototype. It was built inside an old HP server. I realized I didn’t need the sides as much as a plenum underneath. This is a working amp- the odd blue form is a welding rod container wrapped with 6 ga wire. It’s my first filament choke.

Protype Running

After some success with a prototype I bought some stock- 60′ of 1 1/4″ angle iron, a 4′ x 8′ sheet of 16 ga sheet metal and one of aluminum.

Raw Steel

It took far longer to fabricate the frame than I had figured on.

Amplifier Frame

Here it is with skins.

3CX3000 HF Amplifier

First layout RF deck-

RF Deck 3XC3000

Second layout RF deck- stacked cap give more room for the magnetic fields crated by the roller inductors.

3CX3000 Amp

Filament choke

Filament Choke 3CX3000

Using the amplifier’s frame to bend the aluminum plenum

Bending Plenum


Plenum Fitting

Plate choke is off the shelf similar to Ameritron’s

Plate Choke with Eimac 3CX3000

Tube socket is from a Continental 317C.  I’ve relieved the sides to increase air flow

Grounding Grid

Building the Pi input board from WD7S.  The enameled wire is not included-  I stripped some from transformers

Pi Input Board

Input Pi finished and mounted under 3CX3000A7.  It’s an ideal location- air cooled and connected with only the capacitor’s leads

Input Pi WD7S

3CX3000 center tapped filament transformer from a Continental 317C.  It was designed for this tube- though an A1 as an audio modulator.

Filament Choke

A working amp

Able to Run