THIS PROJECT IS DEPRECATED. DO NOT USE IT WITH ANGELIA/ALEX ARCHITECTURE (could be used as a simple lpf with notch for any other short waves sdr project
Alex RX 7th order lpf with 88-108 rejection notch
This repository contains the High Pass Filter project of the OpenHPSDR Alexiares frontend
Originaly, this filter is located on the RX, HPF board of Alexiares. As the size of this hpf board is limited, it has been decided to put this lpf and the TX/RX relay (RXpath and Pure Signal path) on a specific board.
The filter is a 7th order lpf with 2 notch rejection frequecies centered on the FM broadcast band (88 and 108 MHz). Thus, very strong FM radio station will not be received in the 4th Nyquist zone of the SDR.
A "watertight" rf shielding could be placed around the board or around the filter itself.
The file lpf input.PNG gives a simulation of this filter
Part of this work is protected by the TAPR Open Hardware Licence https://www.tapr.org/ohl.html
Original work by Graham Haddock, KE9H and Phil Harman, VK6APH.
Board's dimensions are undersized to fit the 10x10cm size of all board of the Hermes project under Kicad:
AlexI2C
Alexandrie
Alexiares_Coax_Out
Alexiares_HPF
Alexiares_LPF
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