Four State QRP Group

Four State

Hi-Per Mite

An Active Audio CW Filter
Designed by
David Cripe, NMØS

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Kitted and Offered For Sale By The Four State QRP Group

The HI-PER-MITE is a HIgh-PERformance SMALL audio filter. It is designed to be very versatile, have low parts count, be inexpensive, yet provide outstanding performance. This is a flexible design that can be used as a stand-alone unit driving headphones, earbuds, or speakers, or it can be easily integrated into an existing receiver needing additional CW filtering (see manual for details).

Designed by David Cripe NMØS, it features a 200 cycle bandwidth with NO RINGING! It can be used as an external stand-alone unit with an onboard audio amp for driving a speaker or headphones. It also can be built into a receiver without using the audio amp, or with it if you need an audio stage. This is a very useful accessory for direct conversion or other rigs needing additional selectivity. It removes/reduces signals and noise outside the 200HZ passband, and also power line hum in Direct Conversion receivers. Thus providing comfortable listening while using earbuds, headphones, or a speaker. If you have a direct conversion receiver, you will love this filter.

The HI-PER-MITE is a much improved version of Dave's HI-PER Audio Filter circuit that was published in the May 1994 issue of 73 magazine. If you wish to learn more about the genesis of the HI-PER Mite, and learn about important audio filter design parameters, click on the original 73 article link in the documentation section below.

This low cost kit sacrifices nothing in the way of quality. It features a high quality printed circuit board, low parts count, all through hole parts, and fast and easy building. It is an excellent kit for first time builders, and was chosen as the Buildathon kit for OzarkCon 2012. First time builders please note: This kit is not difficult to build, there are NO SMT parts and the parts are wide spaced on the board making installation easy.

    Specifications and Design Features
    Bandwidth:  200 cycles at the -3 DB bandwith points.
    Center Frequency:  The center frequency in the passband is 700 HZ
    Signal Gain:  0 dB to 50 dB, user selectable
    No Ringing or Buzz:  Nice, smooth audio - care has been taken in the design to eliminate ringing.
    Versatile:  Drives speaker, earbuds, or headphones. Use standalone or install inside rig.
    Audio Power:  500 mW into 8 ohms, from 9v supply
    DC Power:  5 to 13 VDC at less than 15 mA
    NO SMT Parts:  All through hole parts..
    NO Toroids:  There are no toroids to wind, special circuits simulate them.
    PCB:  High Quality, silk screened, two sided 2.2"x1.5" printed circuit board.

    Assembly Manual
    Parts List
    Assembly Manual in Spanish Translation by Jon Iza EA2SN, thank you Jon.
    Parts List in Spanish Translation by Jon Iza EA2SN, thank you Jon.
    Assembly Manual in Portugese Translation by Ed Freitas PS7DX, thank you Ed.
    Part Layout
    Want a different center frequency? Here's How.
    Center frequencies in Spanish Translation by Jon Iza EA2SN, thank you Jon.
    Center frequency Calculator by Paul Jorgenson, KE7HR.
    AA7EE Dave Richard 's incorporation into a DC receiver.  Posted with permission, thanks Dave.
    AA7EE Dave Richard's YouTube video of the Hi-per-Mite in action.  Posted with permission, thanks Dave.
    BX2ABT Hans Fong's You Tube Video Review  posted here with permission.  Thanks Hans.
    75 wpm dit performance by Chuck Vaughn, AAØHW posted here with permission.  Thanks Chuck.
    Audio Bandpass Test by Chuck Vaughn, AAØHW This is an audio file and a must listen,  Thanks Chuck.
    K9PL's Review  in the K9YA Telegraph  (posted here with permission)  Thank you Philip.
    NMØS Original article in 73 Magazine  click to turn the pages.
    Photo Page

    Electronics 2000's Excellent Capacitor Identification Page  Posted with permission.
    Electronics 2000's Excellent Resistor Code Graphic Calculator  Posted with permission.
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If paying by check or money order
(US dollars only) please make it out to "Four State QRP Group" and send to:
Four State QRP Group
Ron Potter AG1P
PO Box 1117
Fernley, NV 89408

Due to high bank processing fees, we can no longer accept Canadian Money Orders.

The Hi-Per-Mite is carefully kitted and shipped by Gene Sylls, KG6EYE
Please direct kit and part related questions to Gene
All proceeds are applied toward funding OzarkCon.   Thank you for supporting The Four State QRP Group.
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