Amateur radio is one of the most exciting things to do. When a radio receiver, assembled from a pile of disparate parts, suddenly comes to life, its creator experiences genuine joy. And given that the design of the receiver can be complicated and improved almost endlessly, there will be a lot of reasons for joy.
Instructions
Step 1
To assemble the radio, find its schematic diagram or follow exactly the description below. The simplest is the assembly of the detector receiver, which does not even require batteries, so it is better to start with it. It is powered by currents induced in an external antenna. Pre-make the antenna, you will need a coil of wire in varnish insulation with a diameter of about 0.5 mm.
Step 2
To make an antenna, stretch the wire ten times between two hammered nails, suitable hooks, etc., located 7-10 meters from each other. Then remove the wires from one of the nails, clamp them into the drill and twist the antenna cord. It will need to be pulled between porcelain insulators on the street - for example, on the roof of a house, between the roof and a tree, etc. And from the rope to enter into the house a reduction wire, through which radio waves will enter the input of the receiver. If you live in an apartment, the antenna can be placed around the perimeter of the window or pulled over the ceiling.
Step 3
In addition to the antenna, you need a ground connection. In an apartment, they can serve as a heating radiator pipe - clean it with a file and screw on the wire. In a private house, good grounding can be done by soldering a wire to an old bucket and burying the bucket in the ground. Pour a bucket of water into the hole before burying the bucket. The ground and antenna wires should fit neatly to the location where you will mount the radio.
Step 4
To mount the detector receiver, you will need a piece of ferrite rod about 7-8 cm long and about a centimeter thick, you can take it from an old factory radio or purchase it at a radio store. A paper frame is wound around the core with glue - so that the core can move in it with some effort.
Step 5
Wind about 80 turns of wire with a diameter of 0.2 - 0.3 mm on the frame with the inserted rod. Secure the ends of the wire with electrical tape. You have received an inductor, it will be used to tune a station in the mid-wave range. For longer wavelengths, the coil should contain approximately 300 turns of wire (a longer rod will be needed).
Step 6
In parallel with the coil, connect a capacitor with a capacity of 120-150 pF (picofarad). Connect one terminal of the coil to ground and from it, let it go to high-impedance headphones (TON-2 and the like with a resistance of at least 1600 Ohm). The second output of the coil is connected to the antenna and from it goes to the anode of the point diode. The diode cathode is connected to the second headphone output. Connect a capacitor with a capacity of 2200 to 6800 pF in parallel to the telephone connector.
Step 7
The detector receiver is ready! Put on your headphones and start slowly moving the ferrite bar inside the coil. The parameters of the oscillatory circuit, consisting of a coil and a capacitor connected in parallel to it, will change in this case. As soon as the frequency of the loop matches the frequency of the radio station, you will hear the radio transmission in the headphones.
Step 8
For experiments, the receiver can be literally mounted on the knee. But it's better to get used to doing everything neatly and reliably right away. The base for the receiver can be a piece of cardboard: pierce the holes for the leads of the parts, solder them from the bottom with a mounting wire.
Step 9
The fixed capacitor in the oscillating circuit can be replaced with a variable capacitor, then you can tune in the station by rotating the capacitor knob. Over time, you can add a simple one or two transistor amplifier to the receiver, which will greatly increase the volume of the sound. But to power such a receiver, you will need a battery.
