How do I make a mini walkie-talkie? - The walkie-talkie, a portable two-way radio, consists of three blocks, namely receiver, transmitter and modulator (amplifier). The former is a super regenerative receiver (Figure 1). Using this circuit, gains of more than 10000 times can be achieved. The output voltage is over 20 mV. In the receiving state, the signal from the receiver is fed to the AF amplifier.
The DC-coupled amplifier (Figure 2) has an amplification factor of 500 . When using a 150 L> speaker in the final stage, you get about 70 mW output power, which is also suitable for playing a walkie-talkie enough. During transmission, the loudspeaker is at the input of the amplifier, so it works as a microphone. Because of the high amplification of the circuit, which
now works as a modulator, a sufficient degree of modulation is obtained when speaking from a normal distance to the microphone (loudspeaker). The output signal is now sent to the transmitter.
The transmitter (Figure 3) is a quartz-controlled oscillator with an oscillating frequency of 27.125 MHz. The quartz ensures an extremely constant frequency.
The LF signal is superimposed on the HF carrier frequency via the collector.
If there are no obstacles to the If the carrier frequency is between the interlocutors, you get a range of about 1 kilometre. In residential areas, this is a few hundred meters.
During assembly, the receiver and amplifier can be placed in one housing. It is important to ensure that there is a short distance between the two; shielding
by means of a copper plate is to be provided.
An antenna with a length of 70 cm should be used for a compact design and good matching. We expressly point out that for the operation of the transmitter,
no matter how small, a permit must be obtained from the Federal Post Office.
The DC-coupled amplifier (Figure 2) has an amplification factor of 500 . When using a 150 L> speaker in the final stage, you get about 70 mW output power, which is also suitable for playing a walkie-talkie enough. During transmission, the loudspeaker is at the input of the amplifier, so it works as a microphone. Because of the high amplification of the circuit, which
now works as a modulator, a sufficient degree of modulation is obtained when speaking from a normal distance to the microphone (loudspeaker). The output signal is now sent to the transmitter.
The transmitter (Figure 3) is a quartz-controlled oscillator with an oscillating frequency of 27.125 MHz. The quartz ensures an extremely constant frequency.
The LF signal is superimposed on the HF carrier frequency via the collector.
If there are no obstacles to the If the carrier frequency is between the interlocutors, you get a range of about 1 kilometre. In residential areas, this is a few hundred meters.
During assembly, the receiver and amplifier can be placed in one housing. It is important to ensure that there is a short distance between the two; shielding
by means of a copper plate is to be provided.
An antenna with a length of 70 cm should be used for a compact design and good matching. We expressly point out that for the operation of the transmitter,
no matter how small, a permit must be obtained from the Federal Post Office.
Reference : https://archive.org/details/elektor197101v005/mode/2up?view=theater
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