Ham radio enthusiasts use radio amplifiers to strengthen their broadcast signals. High Frequency (HF) amplifiers operate between the 3MHz and 30MHz frequency bands, in the frequency range reserved for amateur, ham radio. Solid state amplifiers use transistors instead of tubes. The transistor is an integral part of the amplification circuit. It scales up the input signal so that it is strong enough for broadcast. Building your own solid state high frequency amplifier kit gives you scope for customisation.
- Skill level:
- Moderately Challenging
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Things you need
- Chassis enclosure
- Copper heat-spreader plate
- Blank circuit board
- IEC power supply
- Frequency meter
- Relay coils
- Dremel tool
- Standard electric drill
- Drill bit set
- Soldering iron
- Wire cutters
- Phillips screwdriver
- 4-40 gauge screws
Source your parts. Purchase them individually or as part of a project kit. The advantage of the latter is that project kit parts are made to measure and typically come with wiring schematics.
Load the circuit board. Fit the board in your bench clamp so there is at least a 1-inch gap between the base of the board and the work bench. This enables the connector pins to poke through. Load the resistors first, then capacitors, transistors, relay coils, fuses and potentiometers. Push each component into its turret with enough force so that the connector pins slot through the holes and protrude out of the base.
Clean the tip of your soldering iron with a wet sponge and dry it with a cotton cloth. Turn it on and let it heat up.
Remove the board from the bench clamp and place it face up. Gently press each connector pin so that it sits flat against the copper strip on the base of the board. Dip your soldering iron tip in solder and gently press the tip against the connector pin so that it fuses to the copper strip.
Prepare the chassis. Calculate the surface area of the frequency meter, jacks and IEC power supply socket. Plot a mounting hole outline for each on the side of the chassis. Use a dremel tool to cut out mounting holes for the IEC power supply and frequency meter. Use a standard drill bit to bore the holes for the jacks. The size of the jack will determine which drill bit you use.
Cut four pieces of power wire. Strip each piece at the end to expose the metal. Solder one piece to the output terminal of each chassis-mount component.
Load the chassis. Fit the chassis-mounted parts onto the chassis. Slot them into the mounting holes so that the wires are inside.
Screw the copper heat-spreader plate into the base of the chassis. Screw the circuit board onto the copper heat-spreader plate.
Solder the frequency meter wire to the transistor. Solder the IEC power wire to the first positive eyelet on the board. Solder the input jack wire to the first resistor in the signal chain. Solder the output jack wire to the final resistor in the signal chain.
Screw the chassis enclosure onto the chassis base.
Tips and warnings
- Use emery paper to clean the connector pins before soldering. Untidy solder joints can lead to radio interference.
- Always solder in a well-ventilated area.
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