80 meter bandpass filter

After putting up my efhw antenna, I wanted to test a few other bands. I’ve never done much with 80 meters, so I figured I’d give it a try with a raspberry pi WSPR transmitter.

To do that, I needed a filter for 80 meters to suppress the harmonics from the square wave from the raspberry pi.

I found a good video by ZL2CTM showing his experiments with an 80 meter bandpass filter.

The schematic is below.

I built up the filter and tested it with my nano vna.

You can see a pretty good dropoff after 4MHz.

I fired up the raspberry pi at 10mW and was surprised to get a few spots even though it was storming out.