Experimental Transmitter (MIN490E)

   We describe the assembly of a dipole transmitter without coils in a contact array of 170 points using the 4093. With it we can learn how a high frequency oscillator produces radio signals or electromagnetic waves that can be picked up by a common AM radio.

  Oscillating at a frequency of a few tens of kilohertz, the 4093 produces a signal with a rectangular waveform, that is, a signal that varies very rapidly from high to low. This makes this signal, in addition to the original frequency, called fundamental, also produce signals of multiple frequencies, called harmonics.

   These frequencies correspond to double, triple, quadruple, etc. of the fundamental frequency reach the average waveband used in radio. Thus, if we apply the signal of this oscillator in a small antenna it radiates these signals in the form of electromagnetic waves and they can be picked up in a common radon out of season.

   The transmitter is very weak and has no fixed frequency, so the range is only a few tens of centimeters.

 Assembly

    In figure 1 we have the complete diagram of this experimental micro-transmitter with the 4093.

  Figure 1 - Diagram of the micro-transmitter

The appearance of the assembly on the 170-point protoboard is shown in figure 2.

Figure 2 - Mounting on the terminal bridge | Clique na imagem para ampliar |

When assembling, it is important to observe the position of the integrated circuit and to dock it, do it very carefully so that all the pins are aligned with the holes. When we press the integrated circuit all the pins must fit effortlessly.

      The antenna consists of a piece of wire about 15 to 25 cm long.

  Checking the Operation

   Take a transistorized radian that has the average waveband (AM) and tune to a point where there is no transmitted station. You will only hear a background noise that corresponds to the atmospheric noises and the radio circuit itself.

   Approaching the antenna radon of the transmitter you should pick up your signal in the form of a whistle.

Material list

CI-1 - 4093 - integrated circuit

R2 - 1 k ohm - resistor - brown, black, red

C1 - 22 nF - polyester capacitor

B1 - 6 V - 4 batteries

Several:

Protoboard, support of batteries, wires, etc.