Today’s Saturday project was to solder up ugly style a 20m RF amplifier that resided on my bench for like six months. It’s been nearly a decade since I did anything ugly or Manhattan style. This project was actually an excuse to design a RF low pass filter and test it with my Rigol spectrum analyzer. The screen shots below show that the first harmonic is suppressed by 26db. Mysteriously, there is a harmonic below the primary frequency. I used a 2N3866 power transistor. This are getting hard to find, but I’ve managed to get a supply from Aliexpress.
Edit 2014-12-25:
I used the low pass filter to test the miniVNA Pro. Here is what the loss response looks like:
