DIY Radio 2019

River City ARCS DIY Radio Builders

Bob Mix KF6ABC's 2019 DIYRadio Builders' Group for River City ARCS Club Members

During his April 2019 meeting presentation, homebrewer Bob Mix, KF6ABC shared a glimpse into the joy that he helped many experience in the Bay Area Radio Builders' Club.  Bob led club members in a beginners' DIYRadio group to learn and share the joy and adventure of building eight simple electronics and radio circuits.  

Online discussion group
Facebook group

April 2019 KF6ABC Hands-On Circuits Presentation

Course Description

The notes below describe the start off of this special interest group of RCARCS. I welcome any and all ideas. The first 5 circuits will be assembled on a prototyping board reusing parts. The Pipsqueak and Pixie can be soldered into permanent radios, at least that's what I intend to do. Please comment. I always welcome criticism and am eager to hear better ideas.

Audio circuits are simpler than radio frequency circuits and results are in the range of human hearing. The first 2 circuits will be audio oscillators. The first one will be based on an IC and can be used as a code practice oscillator. The 2nd one will instead use a transistor. Builders will hear results or else silence will denote a bad component or a failure in assembly. The free Zeitnitz Soundcard Scope will be demonstrated generating audio signals. The free LTSpice software will be used to simulate circuits. Simulated output signals will be compared to actual signals displayed on a digital storage oscilloscope and a frequency counter.

Builders will supply earphones, a 9-volt battery and wire (#24 solid?). Participants will receive all the other needed components and a prototyping board.


In any project, it's best to start with fundamentals. Personally, I seem to clarify my thinking when I get back to basics. From a better foundation, I can then with confidence build a stronger mental structure. Knowledge is good for its own sake, but the purpose of this group is to put it into practice building working radios. Those who attend meetings should not be intimidated and we should welcome observers who keep their hands off circuits.


  1. Raise all members to the same knowledge and skill level
  2. Build radios and use them to QSO each other
  3. Learn how radios work
  4. Learn to use the best tools available

The goal of this sub-club is to get all builders to know how to build radios from circuit diagrams and understand how radios work after knowledge flows through the hands up to the brain. Theory is just theoretical until it is put into practice. This course involves assembling 8 circuits, 6 on a prototyping board and 2 (a transceiver and a shortwave receiver) soldered for permanent use. Once assembled, each circuit will be subjected to experiments that will demonstrate basic radio building blocks in action. Electronic legos. Radios are built from FOAM, an acronym for Filter, Oscillator, Amplifier and Mixer.

Curumim Transceiver
Circuits (from simplest to most complex)

  1. LM386 square-wave audio oscillator for code practice
  2. Twin-T one-transistor audio oscillator
  3. LM386 amplifier for the Twin-T
  4. BD139 amplifier for the Twin-T
  5. RF Oscillator
  6. PY2OHH Curumim CW Transceiver
  7. Pipsqueak Regen Receiver (pages 12-15)
  8. Pixie 2 CW Transceiver
  9. Arduino Clock (additional cost)

Pipsqueak Receiver

  1. Extech EX330 DMM
  2. Soundcard Scope software
  3. Digital Storage Oscilloscope
  4. Elecraft XG3 RF Signal Source
  5. CountyComm GP5
  6. LTspice Circuit Simulation software

Pixie Transceiver
Basic Skills

  1. Reading schematics
  2. Reading datasheets
  3. Identifying components and their values
  4. Static safety
  5. Understanding the prototyping board
  6. Assembling circuits from schematics
  7. Using a DMM
  8. Operating a scope
  9. Debugging circuits
  10. Soldering
  11. Desoldering
  12. Testing


  1. for most components
  2. for the MB-102 prototyping board
  3. for ham band crystals
  4. for variable capacitors (e.g. 14VCRTRF-10-280P)