You can start your acquaintance with the fascinating world of radio by making simple circuits that will give a good practical experience to a beginner radio amateur. To begin with, you can assemble a detector receiver, its manufacture has long been a good tradition among radio amateurs. It is easy to make and can be made in just a few hours. This requires a minimum and accessible to everyone set of parts and, of course, the desire to work. The first prototype detector receiver is different because it can be modified, does not require PCB design and fabrication, and is easy to set up because all the parts fit on the table.
Let's prepare the parts necessary for the manufacture of the device. The detector receiver consists of a semiconductor point diode (D9, D2), which will be the detector. A set of capacitors with a capacity of up to several thousand picofarads, a ferrite core (7-8 mm in diameter) of the 400HH, 600HH brand and up to 140 mm long. You also need to prepare a wire of the PEV-1, 2 brand (0.15-18 mm) and any high-resistance telephones with a coil resistance of at least1500 ohm. All these radio components can be purchased from a specialized store.
Now let's focus on making a coil for a ferrite rod. To do this, we wind several layers of loose paper on a ferrite rod and glue them together. You should get a dense frame that can be easily removed from the rod. Now we wind three hundred turns of pre-prepared wire and make taps every five turns. The main mistake of those who make their detector receiver for the first time is that every fifty turns the wire is cut off, stripped and tinned. Leave this operation for later, in the process of winding it is enough to make taps and continue to wind the wire. The resulting coil must be glued with paper glue and allowed to dry.
Now let's assemble all the details according to a simple scheme. We connect the extreme tap of the coil and the anode of the diode to the receiving antenna. We connect the other extreme tap to ground and one of the headphone leads. The second output of the headphones is connected to the cathode of the diode. That's it, you have assembled your first radio receiver with your own hands. If all receiver circuits are assembled correctly, it starts working immediately. We adjust the device by changing the number of turns on the coil and select the capacitance of the capacitor, which we connect in parallel with the headphones. With this we achieve the best sound.
This receiver is good at picking up radio transmissions from nearby stations operating on the medium and long wave bands. The next step maybe the manufacture of one-, two-, and more cascade receivers that can receive a much larger number of stations. And in the future, you can make a scanning receiver that automatically finds the station and remembers it. The more complex the circuit of the device, the greater the possibilities in it. But to properly set up such a receiver, you need to have good test instruments in your home laboratory, a high frequency generator, an oscilloscope, etc.
