Bandpass Filter Picture

This Bandpass Filter covers 7 bands. The top filter covers 20, 15, 12, and 10 meters. The bottom filter covers 40, 30, and 20 meters. The Bandpass switch shows 40/30/17 but should read 40/30/20. This mistake will be fixed on future boards.

The board features IR switching with IR emitters and photodiode receivers to increase isolation between the filters.

Reed relays are used here to also increase isolation between the filters. Reed relays are encapsulated in a glass envelopes with an inert gas so that a wetting current is not needed to provide long term service. See Reed Relays, a paper from National Instruments on Reed Relays and the need for Wetting Currents.