Building your own one-tube short wave radio receiver is a worthwhile first radio project for those with a basic understanding of radio electronics. Amateur extra class operator David Schmarder points out on his Make a Radio website that modifications to specifications and components will allow you to customise your radio. You can construct an enclosure for permanent use. Once you understand the basic parts of a simple one-tube receiver, you will have the basis in radio theory to move on to creating a two-tube or integrated circuit receiver with little difficulty.
- Skill level:
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Things you need
- Soldering iron and solder
- Small wire cutters
- Small wire stripper or pocket knife
- Small needle-nose pliers
- Hand drill and 1/16-inch bit
- Roll of black electrician's tape
- 6- by 9-inch solderless electronics breadboard or 6- by 9-inch wood block and small wood screws
- 5 9-volt batteries with connectors
- 1.5 volt D-cell battery with connector
- 1T4 amplifier tube with base
- 3-inch length of 2-inch outside diameter cardboard or plastic tube
- 10 feet of uninsulated No. 23 solid copper "coil" wire
- 10 feet of insulated No. 22 solid copper "hookup" wire
- 1K Ohm resistor
- 1M Ohm resistor
- 50K Ohm potentiometer
- 22 picofarad variable (tuning) capacitor
- 20 picofarad variable (trimmer) capacitor
- 27 picofarad capacitor
- 100 picofarad capacitor
- 2 .001 microfarad capacitors
- 2.5 Millihenry RF choke
- 2 Double pole single throw switches
- Small speaker or headphones
Lay out your materials in a well-lighted and ventilated area away from small children and pets.
Place the five 9-volt batteries together side-by side with the positive and negative terminals aligned. Wrap them with electrician's tape to form a bundle.
Connect the 9-volt battery connector wires in electrical series twisting the wires together results in an output voltage of 45 volts when attached to the batteries.
Solder the twisted connections and wrap them with electrical tape for insulation.
Drill two 1/16-inch holes near one end of the 2-inch tube. Feed the uninsulated No. 23 copper wire in through one hole and out through the other, tying a knot to hold it.
Wind 14 turns of uninsulated No. 23 copper coil wire around the 2-inch tube to create the primary coil. Repeat Step 1 to secure the end of the winding.
Wind four turns of No. 23 copper wire one-half inch below the first coil to create the tickler coil, using the same process as was used to wind the primary coil.
Position all components on a breadboard or wood block. The physical layout is unimportant but components should be positioned to allow for simple and direct wiring paths.
Mark the positions of all components, measure the distances for the wire connections, and cut the appropriate lengths of insulated No. 22 hookup wire.
Strip one-quarter inch of insulation from each end of the hookup wires and flow a small amount of solder onto each bare end to create a clean electrical connection.
Install and wire the components from the centre of the layout outward, starting with the components you have positioned in the centre of the breadboard or wood block. Use the schematic diagram in Reference 1 to identify connection points.
Connect the wires between the components by bending or twisting then. Solder the joints as needed.
Place both battery switches in the open (off) position and install the 9-volt battery pack and D-cell battery.
Install the 1T4 tube carefully into the socket base.
Tips and warnings
- Soldering irons operate at about 204 degrees C and solder can give off noxious fumes.
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