C.A.L.F. the Configurable-Audio-Limiter-Filter
club project kit
a really fine development by John Clements, KC90N. ( KC9ON.com )

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*** download-> CALF article published in QRP-Quarterly ( PDF )

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This is John Clements' "CALF" in Action with my HW8. December 27, 2014 .
Designed with a Preamp,
an Active-Limiter ( instant action ) with 3 LED indicators,
up to six stages of Switch Selectable MFB filtering,
and a user-controlled LM386 Audio chip. .

Option for direct Soldering of Filter components which allows a standard kit-out-of-the-box project.
Components are 1% and CenterFreq is within 15 Hz of true, right out of the box !

Below view is the layout of the Front Panel of the Cw Audio Limiter Filter project kit by John Clements, KC90N

$KC9ON_CALF-FRONT-med-{}.jpg$

Below view is with Socketed attachment of Filter components by which John allows for experimentation.

$KC9ON_CALF-LEFT-sockets_med-{}.jpg$

Below is a view during assembly, my wife's fingers,
inserting custom components into a socket which is then inserted onto the PCB of the CALF.
This is the my method of customizing the PassBand Shape.
Possible to have 2 or 4 or 6 filter stages.
Convert to Low-Pass or extreme high "Q" !
Experimenters paradise ! and guaranteed to function !

Option for direct Soldering of Filter components which allows a standard kit-out-of-the-box project.
Components are 1% and CenterFreq is within 15 Hz of true, right out of the box !

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These are the latest pics from the KC9ON site, also presenting the "CALF BARN" enclosure !

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CALF article published in QRP-Quarterly ( PDF )

CALF Original Schematic here:

Original Calf Spice Bode here : (matches my O'scope measurements )

Original CALF Transient plot here : ( observe the dark-orange trace for sharpest filter stage)

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"Ultimate" circuit built onto the KC9ON CALF PCB project.

Examine the AFV project for details about this circuit, as CALF is an early version of the AFV circuit.

* Magnitude Plot shows depth of Dual-Notches which surround the Central-PassBand Peak.
* Notch are -54 dB down !!!
* BandWidth @ -3dB = 80 Hz, BandWidth @ -54dB = 385 Hz.
* SideBands expand at 6 Hz per -dB attenuation.
* This is as Brick-Wall as any DSP when signal is finally driven through an audio-speaker to listen.

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C.A.L.F. the Configurable-Audio-Limiter-Filter club project kit a really fine development by John Clements, KC90N. ( KC9ON.com )

Option for direct Soldering of Filter components which allows a standard kit-out-of-the-box project.Components are 1% and CenterFreq is within 15 Hz of true, right out of the box !

C.A.L.F. the Configurable-Audio-Limiter-Filter
club project kit
a really fine development by John Clements, KC90N. ( KC9ON.com )

Option for direct Soldering of Filter components which allows a standard kit-out-of-the-box project.
Components are 1% and CenterFreq is within 15 Hz of true, right out of the box !