Well this one has been a long time coming. From the very first amp i built till now has been close on 5 years. Those first amps were rather scary contraptions dead bug on scrap pcb and had more than a few fets explode on me. And after the debacle that the 2×4 amp was, this time around i decided to cut it in half and make sure it is all working right and to have the mechanical aspects of the build right also, so if something does break and lets be honest something always breaks, that its easy to fix. I have not really started to push this yet, but atm with conservative biasing, drive and voltage i am getting a respectable 36 watts out. Its been key down for the last 15mins and other than the heatsink needing to be bigger to dissipate the heat its going well.

Here is the schematic.

Here is the PCB as laid out in my ecad of choice.

So rather than try and go the home made SMD route, i just went old school with the mechanical design. What i did was mount the fets loosely to the heat sink, then i snug them up, bent the legs with the pcb and then tightened them all down. It meant i could slide the PCB on and off the legs really easily until i was ready to solder them on permanently. If i fet dies, it should make replacing it a lot easier.

Setup for testing. I kind of just snuck up on it with voltage and drive. 13.8v and 200mw drive and I was getting about 7 watts out. Slowly and surely i brought the voltage up and the drive as well. In the end i was giving it 1 watt of drive at 24v and was getting 36w out. Its got way more to go, but its nice and stable.

A step in the chain, was about 25w here.

60v peak is 36 watts. Now i need to put some 200v caps in the low pass filter and make that look like a sine wave LOL

PDF of the schematic : irf510-2×2-amp

Gerber files for the pcb : REMOVED found an error when I ran 10A through it.

 

Here is the next part of my home brew CW transmitter. An Arduino and AD9850 are providing the DDS VFO signal. Q1 is a buffer to isolate the AD9850. I am not sure that it is needed, but its there to stop the gain stage from loading it up. Q3 is an amplifier that takes the 400mV P-P DDS signal and amplifies it to 8/9V P-P or there abouts into a 50ohm load. Thats about 200mW, enough drive to supply something like the QRP Labs 10w Linear. My plan is to design an amp to follow on from this that will provide 30 to 50w. More on that to come. Q2 is a PNP switch, pulling the base to ground turns lets power flow to Q3 thus keying the transmitter on and off. Simple but works.

Here is the schematic.

The PCB as laid out in Ecad.

Here is the board as built, if you are not colour blind and can read the colours on R5 you will notice i stuffed up here HAHAHA. Also Q1 silk screen is backwards.

Signal output into 50 ohm load at J2. This jumps up to about 10V P-P into the QRP Labs Linear amp. Not sure why yet.

Schematic PDF: CW-Buffer-Amp

Board Gerber Files: DDS-CW-Buffer-Amp

Ok, I have still been working at building stuff. Here is the latest piece of what will become a CW transmitter. These boards are 7th order Chebychev low pass filters.

This is the PCB as laid out in ecad. 4 boards per PCB and you can get 5 PCB from JLCpcb for $2 so that is 20 low pass filter boards. A life times supply.

My current project is a 40m CW transmitter, here is the LPF sitting on top of the TX/RX switch.

Filter response plotted with the NanoVNA.

If you want to have your own LPF boards made, here are the gerber files:  LPF_Singles