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CW-VOX CW-VOX

CW-VOX

Kitted and Offered For Sale By
The Four State QRP Group

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The Four State QRP Group is proud to introduce the CW VOX, based on a project by Kevin Loughin ( KB9RLW ) to make CW more accessible and convenient. This device is a unique blend of technology and creativity that allows keying by voice! It's designed for Morse Code operators who may be afflicted with limitations that make traditional keying methods challenging - or for the operator who wants to try something new and fun!

Concept and Design:

The CWvox is a unique solution that leverages the ability of Morse Code operators to vocalize Morse Code using "da" for dashes and "dit" for dots. This practice isn't just a novelty; it's a skill that, when done correctly, mirrors the proper length ratio of dashes and dots in Morse Code.
The result is a design that can operate as a stand-alone interface to your CW rig. The kit contains a built-in condenser microphone, or it can be used with a microphone headset for added convenience. Its low current draw lets it be operated either from an internal 9v battery, or an external 9 to 12 volt source, not included. The CW VOX has two controls, a power switch, and an audio level setting. An LED is set to flash during keying, so you can easily set the audio level to the proper gain. An additional jack is provided so that you can connect to the headphone output of your rig to pass receiver audio through to a microphone headset, if that is the operator preference.

Theory of Operation:

Audio enters the CW VOX through either the built-in condenser microphone or an optional microphone headset, and is amplified through a variable gain op amp U2 to set the audio level, and then band pass filtered to pass the 300 to 1000 Hz frequencies of vocal vowel sounds. From there, it is full-wave rectified in a saturated voltage follower Q2, and then a peak detector Q3 gives us a signal proportional to the amplitude of the speech input. The comparator U3.1 compares the detected speech level to a threshold, and drives the keying mosfets Q4 and Q5 when speech energy is detected. Hysteresis is provided to this comparator to reduce the sensitivity to background noise or other artifacts. Finally, startup-delay circuit U3.2 disables the keying circuit for 100ms on powerup to prevent erroneous keying.

Specifications and Design Features
Input:	Internal condenser microphone OR 3.5mm, 4-conductor microphone headset (the type sold in dollar stores works well.)
Output:	Open Drain MOSFET keying < 400 mA through 3.5mm jack

Documentation

Assembly Manual, with Schematic,
Parts List, and Photos

Bill Of Materials

Schematic

Posted with permission
Electronics 2000's Capacitor Identification Page
Electronics 2000's Resistor Code Graphic Calculator

Ordering Information:

• The cost of this kit is $ 40.00
with a shipping cost of $ 9.00

• DX Buyers, check HamRadioLand for availability.

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

• If paying by check or money order (US $ only)
please make it out to "Four State QRP Group" in the
amount of $49.00 for each kit purchased,
and mail to:

Four State QRP Group
Johnny Matlock ACØBQ
379 23rd Road
Lebo, Ks 66856

The CW-VOX is carefully kitted and shipped by Kevin Gilot, NZ1I
Please direct shipping, kit, and part related questions to Kevin Gilot

All proceeds are applied toward funding OzarkCon.
Thank you for supporting The Four State QRP Group.

The files and images on this site unless otherwise noted are copyright by
the Four State QRP Group and may not be published or used without permission.