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CW Transmitter

This document describes a multiband continuous wave (CW) transmitter circuit for transmitting Morse code signals in the shortwave band from 5.2 MHz to 15 MHz. The circuit uses a variable frequency oscillator with a coil and gang capacitor tank circuit to generate the carrier wave. Transistors provide the feedback and amplification needed for oscillation and transmission. Winding details for the coil and instructions for building and operating the circuit are provided. The circuit can be powered by a 9V battery and transmits signals that can be received on any shortwave radio receiver.

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213 views2 pages

CW Transmitter

This document describes a multiband continuous wave (CW) transmitter circuit for transmitting Morse code signals in the shortwave band from 5.2 MHz to 15 MHz. The circuit uses a variable frequency oscillator with a coil and gang capacitor tank circuit to generate the carrier wave. Transistors provide the feedback and amplification needed for oscillation and transmission. Winding details for the coil and instructions for building and operating the circuit are provided. The circuit can be powered by a 9V battery and transmits signals that can be received on any shortwave radio receiver.

Uploaded by

chakralabs
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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CIRCUIT IDEAS

MULTIBAND CW TRANSMITTER
REJIMON G. VU2RGQ

SAN

I THE

radio frequency oscillator is at the heart of all radio transmitters and receivers. It generates high-

Fig. 1: Circuit of multiband CW transmitter

frequency oscillations, which are known as carrier waves. Heres a continuouswave (CW) transmitter for transmitting Morse code signals in the shortwave band (see Fig. 1). It is basically a variable frequency oscillator (VFO) whose frequency can be varied from 5.2 MHz to 15 MHz. The signal can be received in the shortwave band by any radio re-

ceiver. The circuit works off a 9V battery. Connect the Morse key (S1) across capacitor C5 as shown in the figure. Attach a telescopic antenna (capable of transmitting over a short distance) at the output terminal. The coil and gang capacitor C2 form the tank circuit. The coil (L) has a total of 60 t u r n s . Winding details are given in Fig. 2. Tappings on the coil allow selection of the required band. The frequency can be varied using C2 (main tuning). On reducing turns of the coil (using selector switch S2), the oscillators frequency increases because frequency is inversely proportional to inductance. Capacitor C1 couples the signal from the tank circuit to the base of transistor T1 (2N2222). Transistor T1 provides

the required positive feedback for oscillation and transistor T2 (BC547) functions as the emitter follower. The output is taken from the emitter of T2.

Fig. 2: Details of the inductor

For stable oscillations, use a polystyrene capacitor as C1. All other capacitors may be ceramic disk type. Enclose the circuit in a metal box for better shielding.

124

ELECTRONICS FOR YOU

JANUARY 2004

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