NEScaf Audio Filter

This is a very capable and user friendly switched capacitor audio filter. It is a kit offering from the New England QRP club, and is very reasonably priced at $35.

This from their web site: The NEScaf is a switched capacitive audio filter based on the MF100 chip. 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.

I built mine stock and in an LMB Crown Royal Series enclosure, with blue top and gray bottom, Mouser number 537-CR-332. These enclosures are very attractive, a little pricey, but more than worth the little extra to house a fine project.

My version is powered from a wallwart power supply with a 12 volt regulator added to the circuit, see the picture at the right. This fine little scaf filter is a valuable addition to the shack for use with rigs with little or no filtering. It more than lives up to the reputation of scaf filters

Revised 27 November 2012 ... WAĜITP
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