CALF the CW Audio Limiter Filter

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Is QRM and QRN getting you down?  Don’t have a cow, get a CALF!

CALF-H-Rear CALF-H-Front CALF-V2-LEFT-M

CALF – the Configurable Audio Limiter Filter – Combines an audio limiter circuit along with up to 6 stages of bandpass filtering to aid in SSB/SWL and CW receiving. Filtering bandwidth ranges from 700Hz to less than 100Hz while the limiter circuit can be used to reduce large static crashes or aid in weak signal reception.

Features:

  • Limiter helps to reduce crashes from QRN or can aid in weak signal reception
  • 6 stages of Op Amp filtering, 5 switch selectable, offering various bandwidths from 700-100Hz on a 700Hz center frequency
  • Built in 1W Audio amplifier drives headphones or a small speaker.
  • Controls mounted on a front panel PCB for ease of use
  • Experimental options:
    • Stages can be split and re-arranged via jumper blocks – Want to put the limiter in the middle of the filter stages? No problem!
    • Optional IC Sockets are included to change and experiment with different R/C values and filter modes – Make Bandpass, Lowpass or Highpass filter stages!

This kit was designed using through hole components and enlarged PCB solder pads for ease of assembly. Included with the kit are several components such as stand-offs, plugs, and jacks to complete the project. Just add your own case!

The story of how CALF was born, links to more pictures, details, audio samples, schematics, assembly manuals, and even drawings for a PCB type enclosure can be found on the CW Reception page.

Read more about CALF in this ARTICLE published in the QRPARCI April 2015 issue of the QRP Quarterly.

CALF-V2-MANUAL – including parts list and schematics

CALF w/ Enclosure

*** ONLY 4 LEFT ***

(with more on the way)

CALF-kit2 CALF-H-Front CALF-E2

Kit $55

Assembled $80


Option



For assembled units choose either:
Fixed - The filter resistors and capacitors are soldered in place
or
Experimental - IC sockets are soldered in place for easy changing of
filter types and values. RC values must be inserted after shipping.

CALF – Kit only (no enclosure)

 CALF-V2-LEFT-M  CALF-V2-right2-M  CALF-kit2

Item: CALF-K   Weight: 8oZ

Kit $36

Assembled $66

(Fixed or Experimental)


Option



For assembled units choose either:
Fixed - The filter resistors and capacitors are soldered in place
or
Experimental - IC sockets are soldered in place for easy changing of
filter types and values. RC values must be inserted after shipping.

 


Corral your CALF!

Keep your CALF from running around with this enclosure.

CALF-E1 CALF-E2

CALF Enclosure

Item: CALF-E  Weight: 8oZ

$24




 


 




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