Electronic filters are circuits which remove unwanted frequency components from the signal to enhance wanted ones. The hairpin topology is a microstrip band-pass filter for the gigahertz band (UHF). They can be very useful with SDR to improve the reception. This video features a Javascript generator for these. It also shows their design and my results.
Original article: http://charleslabs.fr/en/project-Hairpin+filter+design
CC-BY Charles Grassin
Made with open-source software: Kdenlive, Audacity, Inkscape on Ubuntu.