Using a 7400 we have a short-wave transmitter from 4 to 9 MHz, shown in the figure. The coil consists of 9 + 9 turns of 0.3 mm and thick wire (28 AWG, for example) in a 6 to 8 mm tube. The trimmer tunes the signal, which, due to the characteristics of the integrated, produces rectangular waves that are rich in harmonics. Capacitors must be ceramic, and the antenna can be a stretched piece of wire. A transistorized amplification step allows greater power to be obtained for this transmitter.
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