Transmitter in the VHF band. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transmitters
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L1 - 1 turn, but the inner diameter is 6 cm of wire with a diameter of 0,5 mm (so that there are no harmonics).
L2 - 3..4 turns on a frame with a core with a diameter of 5 mm from the IF filters of conventional scoop receivers, wire 0,5 mm.
Antenna - 40 cm copper, 3 mm in diameter. (you can aluminum tube).
Range 64-108 MHz.
The capacitance between the emitter and the collector achieves the maximum radiation power, then it is also achieved by changing the inductance L2, the frequency is selected by the other.
Oddly enough, but this scheme gives 500 m without problems with the correct antenna tuning.
To be more precise, the L2 and C antennas need to be tuned to resonance. this is an open oscillatory circuit, when it is tuned to the frequency of the transmitter, almost all the power of the generator will be in the antenna. and the range will be about 500 m at 12 V power will be even greater.
Judging by the readings of the device (Fig. 2), one can judge the radiation power.
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