A conventional detector receiver sounds very quiet. It is possible to increase the sound volume in the headphones, and at the same time, sometimes the number of received stations, by making a simple amplifier. It will also help in some cases to do without a complex and dangerous outdoor antenna.
Instructions
Step 1
Take just about any low-power Junctional Junction Transistor. Connect its emitter to the common wire, and the collector through headphones connected in series and a switch in the off position - to a power source with a voltage of several volts. If the transistor has an n-p-n structure, there must be a negative pole of the power supply on the common wire, if p-n-p is positive.
Step 2
Make sure your detector receiver is built to meet safety requirements. If an outdoor antenna is used, check if the grounding is correct and if there is a lightning switch. Remember to use it correctly.
Step 3
Instead of headphones (they are now connected to the amplifier), connect a 10 kΩ resistor to the detector receiver as a load. Connect the common wires of the receiver and amplifier together.
Step 4
From the junction of the detector diode and resistor, apply a signal to the base of the transistor through a capacitor with a capacity of about 0.1 μF.
Step 5
Turn on the switch. You will hear a hoarse but loud sound. Try connecting a resistor of several hundred kilohms between the collector and the base, while not soldering it. Try using resistors with less and less resistance until the wheezing disappears.
Step 6
Turn off the power, solder the resistor you chose, then turn on the power again and start using the receiver.
Step 7
If desired, replace the headphones with more comfortable low-impedance ones by re-selecting the resistor.
Step 8
If you do not already have a detector receiver, after building one, immediately make an amplifier as well. Instead of an outdoor antenna, you can use an indoor antenna, which can be built quickly and does not require a lightning switch and grounding.
Step 9
To build a multi-stage amplifier, connect a resistor with the same resistance as the headphones had to the previous stage instead of headphones, then from the point where the resistor is connected to the collector of the transistor through a capacitor with a capacity of 0.1 μF, apply a signal to the base of the transistor of the next stage. The amplifier's sensitivity will increase. To avoid self-excitation, it is not recommended to install more than three stages in the amplifier.
