[CW] NEScaf switched capacitive audio filter

[w9oj at indy.rr.com]

The NEScaf is a switched capacitive audio filter. It is designed to be simple to build and use.

It is more flexible than previous filters for QRP rigs. It has two panel-mounted controls — a single center-detent potentiometer that sets the center frequency of the filter’s bandpass (default value settable between ~415Hz and ~1kHz), and a dual-ganged potentiometer that provides a continuously variable bandwidth control (from ~60Hz to ~1500Hz). This ability to smoothly vary the bandwidth is very useful.

The NEScaf is designed to be driven with a phones or speaker level signal. No hacking into your rig — just connect it to the headphone or speaker output of the radio. This makes it usable with several radios. The board is small enough, at about 2 inches square, to build inside many radios however, if you so choose.


http://www.newenglandqrp.org/wordpress/nescaf-a-switched-capacitor-audio-filter/



73 de Mike W9OJ