LONG LIFE BATTERY-After all the wiring has been checked again
After all the wiring has been checked again
After all the wiring has been checked again, the test work of preparing the circuit can be started.If it is possible to connect this 14 - inch antenna to the FM directional antenna of the receiving stereo radio, the inspection will proceed smoothly.However, even without the directional antenna, the adjustment method of this circuit is very simple.
Put the antenna in the best position and close the switch, then a faint torrential noise can be heard in the earphone, and sometimes FM radio can also be heard.Adjust the variable capacitor CK with a plastic screwdriver until a strong signal is heard.Now use a FM radio produced by the manufacturer to tune it to the same radio station to see what frequency it indicates.Once the two radios receive the same broadcast, they will then slowly tune the frequency of the radios produced by the manufacturer to the low side or the high side of the FM broadcasting section, turning slowly and bit by bit until they receive the broadcast from the other radio station.Next, the self-made radio was tuned to the same broadcasting station, and the frequency was recorded on the self-made radio.When doing this experiment, it is better to use the low frequency end of FM broadcast section.If the home-made radio cannot fall to the low frequency side, the antenna coil can be compressed. Doing so will shift the entire frequency range of the radio to the low frequency band.When the home-made radio just tunes to the low-frequency end of the FM broadcast band, even if the adjustment is completed.The adjusting bolt of the variable capacitor is now rotated in the opposite direction, tuned to the high frequency side in the opposite direction, and tuned to the high frequency 15 as much as possible.Megahertz.If the length of the coil is compressed or lengthened, the tuning range will change accordingly.For example, if the capacitor of the home-made radio is adjusted to the middle of the adjustment range and the received position of a radio station is in the low frequency band of the FM broadcast band, the coil will have to be slightly lengthened to shift the FM band to the high frequency.In a word, your aim is to make the low frequency end of the tuning range of this radio correspond to the low frequency end of the FM band of the broadcasting station.
If the circuit does not work, the polarity of one or several solar cells may be reversed.If there is no sound in the earphone, there must be a wrong connection.At the same time also want to prevent triode or diode connection.In areas where the signal is weak, a tuning range of 88?The 150 MHz RF signal generator connects its output directly to the antenna terminal so that a strong signal can be input to the radio.
After debugging, all the circuits are put in a plastic box.The radio receiver can be tuned with a small variable capacitor, in which case the coil may have to be pressed short or stretched to adjust the inductance.Drill a small hole in the plastic or aluminum housing where the tuning capacitor is installed, and insert a plastic screwdriver into the small hole to make it much easier for the radio to adjust.If a small variable capacitor with a knob is used for tuning, the knob can be used instead of the screwdriver.Since small variable capacitors are sometimes not easy to buy, common size components are selected in this book. In fact, both types of capacitors can work well, while common size capacitors are generally more convenient to adjust.
4 - 22 Amplitude Modulation Radio Powered by Solar Cells
A radio powered by solar cells that can receive FM broadcasts has already been described above.Here is another common way to receive AM broadcasting.Figure EC,
Antenna - copper wire ( more than 10 feet )
CI - 365 PP Variable Capacitance
Diode - Low Impedance Headset
Li - iron oxygen pot rod antenna coil
PCI - Small Rectangular Solar Cells ( Plus MA Output )
Figure 4 - 25 Amplitude Modulation Radio Powered by Solar Cells
4 - 25 denotes such an amplitude modulation broadcasting circuit.It is very similar to FM radio, but because the received frequency range is different, the parameters of the selected coil and capacitor are different, and the circuit has only one level of amplification.This circuit is specially designed for the AM broadcast repeater mentioned above.In practical application, this circuit uses the same power supply as the sound amplifier, so if it is used with the amplitude modulation broadcast sound amplifier, two power supply devices are not needed.As can be seen from fig. 4 - 25, the solar cell connected to the emitter and earphone can also be connected to the solar cell of the microphone.The two circuits can even be mounted on the same circuit board, so the antenna of the AM radio can not be used at this time, but only be connected to the antenna end of the receiver of the loudspeaker.
This kind of device is easy to manufacture and is the same as the method of installing FM receiver above.The picture shows a magnetic antenna, which is easy to buy.This is a bar made of magnet material with insulated wires wound around it.Tuning capacitors are variable capacitors commonly used in broadcast radios, which are also easily available.
As can be seen from fig. t26, the magnetic antenna is mounted on the leftmost side of the circuit board. it uses an antenna
Figs. 4 - 26 are solar cell powered AM radio components fixed with epoxy adhesive.The tuning capacitor is installed beside the coil. If a long-handled variable capacitor is not used, the capacitor should be installed on the edge of the circuit board.The mounting transistor should also be close to the coil.First, install all the above main components.Before installing solar cells, they should be welded and then connected in series according to the connection method shown in fig. 4 - 26. care must be taken not to reverse the lead wires.
The antenna must be properly installed, because the receiving sensitivity and volume of this type of radio are closely related to the antenna.The antenna is made of a soft copper wire, at least 10 feet long, of course the longer the better.If possible, the antenna should be installed vertically ( relative to the ground ).This type of radio has a good reception capacity for local radio stations.A good grounding system can help greatly improve the efficiency of this kind of antenna system.