Quickie-50 Amplifier

Current release version D, and what I currently use with my KX3 to make contacts at 50W CW.  Works FB!

This design is NOT a kit.  I have limited supply of PCB’s that I may sell depending on demand.  They are currently about $15 for a set of bare PCB’s, no components.  I do not forsee enough demand for a kit version of this, so this is very DIY.  The entire design is open source, including both the hardware, software, bill of Materials, etc.  No support is given or implied, I don’t have time to walk people through the building of one of these amplifiers.  If you wish to sell a kit based off this, please do go ahead.  I would ask that you leave my attribution on the PCB’s, unless you do major modifications.  This is my donation to the ham radio community.  The software you will need to open the files is basically just Kicad 4.0 (or 5.0 when it comes out), OpenSCAD, and openoffice/text editors for the BoM / supporting files.

This design is based off a chinese ripoff of a western design (I want to say the original was out of Portugal, but honestly, I don’t know… nor do I really care.  Kudos if it was you, yell at me if you want attribution for the basic IRF530 amplifier).  Here’s a good example of one of the chinese kits:  https://www.ebay.com/itm/DIY-kits-70W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3/282715582606

While these kits state 70W, that’s kinda pushing it, and the IMD will be pretty bad.  But you can get the cores (T1/T2 in my design), FETS (Q2/Q3), and inductor (L1) plus C1/C2 and U1 out of the kit (You can scavenge the 100nF caps as well, but they’re cheap enough, I’d go with the real deal).  I would suggest tossing the silpads they ship with it and the shoulder washers and getting mica insulators and decent shoulder washers as well, the Digikey P/N’s to be included in the next release version BoM.

NOTE:  Don’t put 5W into this design to get 50-70W.  80m:  0.8W input.  40m:  0.7W.  20m:  1.4W, 15m: 2.6W, 10m: 2.6W.  Exceeding the power input will probably blow up your IRF530’s and cost you $2 plus time to repair, maybe the cost of a fuse as well.

It doesn’t come with a heatsink, you get to supply that.  This design basically just takes that kit, adds a minimal amount of protection, some LPF’s, indicators, buttons, MCU, and a tuner.  My version is nice and compact for portable operation.

Known issues (Errata.txt): There are three errors in RevD, that are very minor, only relating to component marking:

The resistor arrays should be either 1k or 2.2k, depending on how bright youwant them. This is R7 and R8 on the LPF board.

The power converter is upside down that supplies 2.5V to the fan

The silkscreen labels for a few of the inductors in the ATU are incorrect. L2 is correctly 6T on a T30-6 core. L4 should be double the number ofturns, 12T/T30-6. L6 is also incorrect, instead of 21T, it should be againdouble, at 24T/T30-6. L1,3,5 and 7 are correctly labeled. You are notrequired to use 24 or 28ga wire. Each implementation can be different. Iwould suggest using the largest wire you can fit through the core to makethe number of require turns in a single layer. In my uBitx_top mod PCB,which uses almost exactly the same schematic/layout, I used 22ga wire forL1-5, and then 28ga wire for L6 and L7 where 24/32T were required. YMMV.

q50_revD.zip is the entire release file, available here.  Please link to my webpage instead of just hosting this file yourself or linking directly to it, in case there are future updates to the firmware or something else.

Youtube videos about this project: