Compared to the GPIO filters discussed in another article in this issue, Mini-Circuits’ 1415-1425 MHz cavity filters are at a significantly higher price point (around $700 at the time of publication of this article), and are designed with professional requirements in mind.
They have resonant structures with very high Q and provide ultra-narrowband filtering, ideal for high-selectivity applications. They also have an ultra-low insertion loss compared to cheaper filters such as those from Nooelec and GPIO. They come in a solid casing, and can be used for transmission as well as reception. Connections are via N-type connectors, rather than SMA connectors, which fits in with the generally more robust construction of the device. There is a very sharp cut-off out-of-band, and the bandwidth 1415-1425 MHz provides more room to accommodate Doppler shift during hydrogen observations in the Milky Way than the even narrower bandwidth of the WT Microwave Cavity Band Pass Filter WT-A11654-Q04, selecting only 2MHz either side of target frequency of 1420MHz (1418-1422MHz).
Manufacturer details: Mini-Circuits®: www.minicircuits.com P.O. Box 350166, Brooklyn, NY 11235-0003 (718) 934-4500 sales@minicircuits.comCavity