Building a DIY 137 MHz Band Pass Filter
Over on YouTube Adam 9A4QV has uploaded a video showing how to build a DIY bandpass filter for 137 MHz. This can help improve the reception of NOAA and Meteor M weather satellites, by blocking strong out of band signals. Adams design is a 132 MHz – 142 MHz Butterworth bandpass filter which gives about 35 dB attenuation outside of the pass band. He’s also posted a write up documenting the filter design on his website.
Lucas Teske recently went ahead and built the 137 MHz filter suggested by Adam. Lucas didn’t have the correct capacitor values so he ended up cascading several in series. His results showed that the filter did improve his reception significantly.
DIY 137 MHz BPF
Hello, how do you design such a circuit for another frequency?
Using 10pcs 10pF capacitors in series to create 1pF is difficult to get. Instead of that you can twist 2 insulated pcs of 2cm standard wire where you will create the wanted capacitance. You can tune such a capacitor by trimming the length of wire or twisting more turns of wire, depending your needs.
Yeah I know, I just wanted to give a shot. But it actually worked pretty well. I still need to do a higher quality filter for my receivings. At least now I can use a LNA4ALL without being saturated by FM Stations or UHF signals.