How to Build a VHF Radio

Written by thomas edward
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How to Build a VHF Radio
VHF Tracking Radio Plus (radio image by dinostock from Fotolia.com)

Building a VHF radio is convenient from a kit with a printed circuit board (PCB) and detailed plans. Everything is included except a battery and headphones. It is a reliable super-regenerative circuit with one transistor for the receiver function and an integrated circuit (IC) for the audio section. The radio can be used for tracking small FM transmitters in model rocket recovery, tune into the aircraft band and the upper portion of the FM band (107 to 135 MHz).

Skill level:
Moderately Challenging

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Things you need

  • VHF 1 receiver kit ($30)
  • Solder iron or gun
  • Solder flux core electrical
  • Wire cutters
  • Needle-nose pliers
  • Screwdriver set
  • 9-volt battery
  • Non-ferrous tool (alignment type for tuning)
  • Headphones stereo

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Instructions

    Building a Very High Frequency (VHF) Radio

  1. 1

    Lay out the kit parts and match them up with the parts list. Display schematics, pictorials and step-by-step instructions. Before starting the kit, note any defects and return for replacement. Group similar parts together and obtain the missing parts, i.e. a 9-volt battery and stereo headphones. Handmake L2 by following the simple instructions on the second step of the kit instructions and solder into the PCB.

  2. 2

    Group components by class: inductors (Ls are numbered and colour coded), capacitors (Cs are numbered and values marked), resistors (R's are colour coded and variables marked), transistor (Q1 is marked), integrated circuit (IC1 is marked), additional items include the PCB, a stereo jack (J1), battery clip (H1), antenna and screw (T1).

    Follow the step by step assembly onto the PCB. Mark installed parts on pictorial in red pen to indicate completion. Solder from the bottom with small amounts of solder to flow to part and printed circuit. Clip off extra lead wire with wire cutters.

  3. 3

    Mount the completed radio to a small wood block or project box. Connect the 9-volt battery and a hissing noise should be heard in the headset. Adjust or tune the radio with a non-ferrous tool changing C1 and C2. Aircraft transmissions are "line of sight" and you may not always hear the closest signals if they are blocked by a water tower or obstruction. Strong local signals may sound garbled. Try reducing the sensitivity to minimum and place the antenna in a down position to cut signal strength.

    The VHF radio can be used for tracking a radio signal location. Model rockets and aeroplanes can be retrieved in this fashion. A small FM 108 transmitter is located on board the model and emits a beeping signal. The VHF radio is used as a direction finder in locating the lost model.

Tips and warnings

  • The completed parts list is with Mouser Electronics (www.mouser.com). However, parts are common and readily available from most electronic parts supply locations.
  • If the kit fails to work, carefully recheck the wiring diagram and PCB board parts placement. Make sure you do not have any leftover parts. Try replacing the transistor, the IC and the battery along with connections to the battery. If all fails, contact the author/seller, Jerry Baumeister, Box 1084, Jones, OK 73049 for troubleshooting assistance.
  • Avoid cold solder joints. Use a magnifying glass to inspect.
  • Limit solder use to avoid overflow on the PCB.
  • Solder is hot and can burn skin. Avoid direct contact.

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