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Nick: Olli  Info
Age: 32
Location: Helsinki

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VHF transmitter CW/AM

Author: Olli
Used time: 10 min
Cost: 0 units of money
Categories: Electronics

I read this article, I had to test the introduced technique by my self in practice:

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Well not really on the broadcast band but I can hear the third harmonic on 96 MHz with my receiver ;)

"o make the signal audible in a cheap AM radio, the computer turns the power to the oscillator on and off 1,000 times per second while sending the dots and dashes of the code, and leaves it off in between the dots or dashes. This modulates the radio signal at a frequency your ears can hear. In AM Low Tone the audio frequency is 500 times per second.

In the CW mode (CW stands for Continuous Wave), the computer does not modulate the radio signal. It just turns on the oscillator long enough for the dot or dash to be sent. In this case, the receiver does the work of converting the signal into an audible tone your ears can hear, by using a circuit called a beat frequency oscillator. Your short-wave radio may have a switch labelled BFO, or SSB, or CW that allows this circuit to operate."


Without any amplifier I was able to have a range of five meters in AM with quite short antennas on the transmitter and radio receiver.

"By replacing the 1 megahertz oscillator with a 28.322 megahertz oscillator, and connecting the transmitter to a large amateur radio antenna (10 meter beam), I was able to send signals from California to Texas."


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