Table of Contents

CRYSTAL SETS TO SIDEBAND

A Guide to Building an Amateur Radio Station

By Frank W. Harris, KØIYE
© Frank W. Harris 2010, Rev 12
(Note: This document is in PDF format. If schematics and drawings appear
to have insufficient resolution, increase the display magnification.)

FORWARD

Table of Contents

Chapter 1

THE FASCINATION OF RADIO

  • Exploring the shortwave bands
  • Growing up in the Morse code era
  • The joy of building it yourself
  • A brief history of radio communication

Henry, Maxwell, Hertz, Tesla, and Marconi.
Fessenden, Edison, Flemming, DeForest and Armstrong
The sinking of the RMS Republic and the birth of ham radio

  • Ham radio in the last 80 years
  • Becoming a radio amateur

Chapter 2

HOMEBUILDING AMATEUR RADIO EQUIPMENT

  • What qualifies as homebuilding?
  • When homebrewing is not appropriate
  • Barriers to modern homebuilding –

Time, frequency stability, and lead inductance

  • Basic electrical knowledge

Magnets and static electricity
Voltage, current, resistance, energy, and power
(Illustrated with drawings of water and mechanical analogies)
Conductors, Insulators, and semiconductors
Capacitors, inductors, transformers, and alternators
Home power distribution, transformers at low and high frequencies

Chapter 3

SETTING UP AN ELECTRONICS WORKSHOP

  • R&D as recreation
  • How to build radios (or anything else) in your basement

Persistence, read books, keep a notebook, and work in small increments2.

  • Minimum tools needed

The ARRL Amateur Radio Handbook
Soldering irons and small tools
Drills & thread taps
Wood carving gouges for making PC boards
>50 MHz Oscilloscope
Frequency counter
Quality multimeter
Lab power supply
Calculator
Lab notebook
Collection of electronic junk
Parts catalogs
Capacitance meter
Test leads and socket boards

  • Nice-to-have tools

RF and audio generators, spice software, and spectrum analyzer

Chapter 4

HERTZIAN WAVES IN THE BASEMENT

  • The nature of radio waves
  • Mechanical and LC electrical oscillators
  • Antenna and transmission line theory
  • Crystal set components

LC tuner
PN junction diode detectors
P-type and N-type semiconductors
Detection of AM signals

  • Homebuilding the parts for a crystal set

The Jamestown diode
The Caribou headphone

  • Revisiting Crystal Sets in 2006

Learning to troubleshoot
Selective tuning

  • Recreating Hertz’s radio equipment

Transmitting and receiving as simply as possible
The 1880 ten-meter communicator

  • Proving that radio waves exist and aren’t just capacitive or magnetic coupling

Demonstrating standing waves to measure frequency

  • Building homebrew transistors

Bipolar transistors, PNP and NPN
Demonstrating power gain
The Boulder Rock Radio3.

Chapter 5

GETTING ON THE AIR

– DECIDING WHAT TO DO FIRST

  • How to earn a license
  • The rules of the homebuilding game – Whatever makes you happy!
  • Picking an HF band

Getting acquainted with the HF ham bands, 160 – 10 meters + 6 meters

  • Instant high quality HF communications
  • VHF/ UHF handheld transceivers
  • Building an antenna

Dipoles, regular and folded
Multi-band dipoles
80 meters when you don’t have room for a dipole
The curtain rod vertical
A multi-band vertical antenna
Lightning protection

Chapter 6

BUILDING A QRP HOMEBREW

  • A single-band, crystal-controlled, QRP module
  • The transmitter mainframe
  • HF construction methods

Making your own PC boards

“Dead Bug” and “Gouged Board” construction
Superglue “Island Boards”

Coax jumpers
Shielded boxes

  • The complete QRP crystal-controlled transmitter
  • Transistor amplifiers and oscillators
  • How an amplifier becomes an oscillator
  • Class A and Class C amplifiers
  • Stabilizing the operating point, bypass caps, and emitter resistors
  • Quartz crystals – the key to frequency stability
  • The 40 meter QRP circuit

Oscillator and buffer

  • Inductors, RF transformers, and impedance matching
  • Tapped toroid inductors

How to wind them (and mistakes you might make)

  • The final amplifier stages for the QRP

Tuned versus broadband – Use both for best results
Bifilar wound, broadband transformers

How to wind them (and how you might screw up)

Ferrite bead RF chokes, expensive RF power transistors, heat sinks, & output connectors

  • Conquering inductors.

Calculating resonance
Calibrating trimmer capacitors
Calculating turns on powdered iron and ferrite toroids
Chebyshev output low pass filters

  • Keying your QRP

MOSFET power transistors

  • A “spot switch” for the QRP

Chapter 7

BUILDING A CODE PRACTICE RECEIVER

  • A simple, direct-conversion receiver

A great first project for a new ham
Excellent sensitivity and good stability
Poor selectivity

  • Adding 700 Hz audio filtering

High pass and low pass filters
Cascaded bandpass filters increase selectivity
Operational amplifiers

  • Building with integrated circuits
  • AM broadcast filter
  • Getting rid of the image

Chapter 8

POWER SUPPLIES

  • Line powered power supplies
    Power supply safety features

Isolation, 3-conductor cords, fuses, switches, ratings

  • Supply performance and regulation

Rectification, ripple, chokes, capacitors, and bleeders
Zeners, linear regulators, switching regulators
A QRP regulated power supply

  • A battery power supply for the radio shack

Solar cell charging, low drop-out regulators
Battery powered shack lighting

Chapter 9

ACCESSORIES FOR THE TRANSMITTER

  • A straight key
  • An electronic bug
  • Building dummy loads
  • “T” type antenna coupler
  • A low pass filter
  • How to stay legal with a homebrew transmitter5.
  • Antenna and power relays
  • Homebrew QSL cards

Chapter 10

VARIABLE FREQUENCY OSCILLATORS

  • Drift is a big deal today
  • Low frequency VFOs drift less than high frequency VFOs
  • JFET transistors
  • The oscillator circuit
  • The buffer, final amplifier, and output filter
  • The 50 secrets of avoiding drift

JFETs, single-side PC boards, cast metal box, multiple NPO caps, small variable caps,
precision voltage regulation, and more

  • Vernier tuning
  • Varactor tuning elements – advantages and disadvantages
  • A precision power supply
  • A voltage doubler power supply for battery use

Square wave generator with a multivibrator
Squaring up the square wave
Charge pump, diode/ capacitor voltage doubler
Schottky diodes for efficiency

  • Temperature compensation methods

Positive coefficient capacitive trimmer compensation

How to adjust the compensator

Thermistor/ varactor temperature compensation

Chapter 11

Building a VFO for the higher bands (PMOs)

  • Old approaches that no longer work

Frequency multiplication
High frequency oscillators

  • Pre-Mix Oscillator method of frequency translation
  • A VFO-controlled QRP module
  • Crystal oscillators are stable, aren’t they?

Crystal oscillator circuits
Butler oscillators and big crystals

  • Mixers, bipolar transistor and dual-gate MOSFET

Optimum drive requirements
Direction of tuning, drift error cancellation

  • Multistage filters and filter/amplifiers
  • The QRP final amplifier stages
  • Spot switches for PMO QRPs6.

Chapter 12

FINAL AMPLIFIERS

  • The basic features of a modern linear power amplifier
  • It looked easier in the Handbook

Linear “noise mode” operation

  • A tuned 50 watt class B amplifier

Ferrite balun transformers

  • An untuned, sort-of-linear, class B, amplifier

Keying the 50 watt transmitter

  • A linear Class AB amplifier, this time for sure

Single Sideband (SSB) needs a linear
Biasing without thermal runaway
Clamp diodes prevent runaway
Mechanical construction

Chapter 13

BUILDING A HOMEBREW HF RECEIVER

  • Building a receiver – an unusual adventure
  • What’s a reasonable goal?
  • An “adequate performance” HF communication receiver
  • Does it have to be so complicated?
  • Planning your receiver

Direct conversion versus superhetrodyne
Why not single conversion?
Start with a single-band, single-conversion superhetrodyne
How do modern digital receivers do it?

  • Receiver construction – build with shielded modules connected by thin coax.
  • The 80 meter preselector

Reception on 80 meter and 160 meters is aided by a tuned transmatch

  • The Variable Frequency Oscillator
  • Mixer magic

Mixers will give you lots of static – and howls and squeals
A practical homebrew mixer made from discrete parts – it’s harder than it looks
Dual gate MOSFET mixers
Not all MOSFETS work equally well
A JFET alternative mixer

  • Crystal ladder filters – essential for CW

All 9.000 MHz crystals aren’t equal
Using the BFO oscillator to match crystals
Switch in filters with a rotary switch

  • The IF amplifier

Lessons learned from a dual-gate IF amplifier
The cascode amplifier strip – variable gain with constant Q

  • Automatic Gain Control (AGC) – not a luxury7.
  • The product detector

Nearly anything works at least a little

  • The AF amplifier – a vital part of the signal dynamic range

Protecting your ears from strong signals
How Hi-Fi should it be?
Driving a speaker

  • HF converters for the other ham bands

Crystal oscillators
Band switching

  • Receiver power supplies

Use a linear regulator, not a switching regulator

Chapter 14

OLD-TECH VACUUM TUBE RADIO

  • How old can radio technology be and still be used on the air today?
  • Why bother with vacuum tubes?

– Glowing filaments, colored plasmas, and Jules Verne glass envelopes

  • Power supplies for tubes

High voltage power supply safety

  • The old-tech QRP transmitter

Vacuum tube amplifiers
The three roles of the triode filament
RF sinewave oscillator
Quartz crystals
Triode and pentode oscillators

  • Old-tech voltage regulation – big, crude, expensive, but beautiful
  • The travails of triode tubes

The oscillator and buffer
The final amplifier – triodes chirp

  • The transmitter power supply

An inadequate supply from a 1935 radio
A good power supply made from cheap, modern, boring parts
How to check out junk power transformers
A complex but adequate supply made from ancient parts

  • It works! No one suspects it’s old and it’s a success on today’s 40 meter band
  • An old-tech receiver

A super regenerative receiver made from ancient tubes
The power supply
Super-regen on the modern hambands

Lots of fun, but not up to modern QRM & QRPs – back to the drawing board!

Chapter 15

THE NOBEL PRIZE FOR SIDEBAND

  • It can’t be that hard! Want to bet?8.
  • The sideband generator – how it works

The 9 MHz oscillator / amplifier
The audio amplifier
The balanced modulator
Building your own crystal ladder filter
Decoupling the power supply leads
Getting rid of RF feedback – RF filtering for all inputs

  • Tuning and testing
  • Using the generator for AM modulation and CW
  • Moving the 9 MHz SSB signal to a hamband

Move the SSB only once!

  • No wonder most ham rigs are transceivers
  • Moving the 9 MHz signal to the difficult HF hambands

Move the VFO first, then mix it with the SSB 9 MHz.
Pick your oscillator and VFO frequencies carefully
Hearing your own VFO in the receiver
The hardest band – 17 meters
40 meters and 12 meters
Covering the widest band – 10 meters

  • A linear sideband QRP, VFO-tuned module

All stages must be linear and low distortion
All gain stages should be broadband to prevent oscillation
Sometimes high pass filter output is needed and not the usual low pass
Checking out the generator

  • Driving a 50 watt linear amplifier

Chapter 16

ANCIENT MODULATION & OTHER TOPICS

  • Defining amplitude modulation
  • AM modulation for vacuum tube final amplifiers

Plate, screen, & cathode modulation

  • A “collector modulator”
  • Converting a MOSFET keyer into an AM modulator
  • Generating AM with an SSB balanced modulator

Compensating for non-linearity

  • Compression by accident

You probably don’t need to build a voice compressor

  • Ham TV – The old way.

Fun with an ancient flying spot scanner TV camera.

  • Getting on 60 meter sideband – lots of work, little reward
  • PIC programming and class D audio amplifiers
  • In conclusion,

Homebrew ham radio is never complete – when it works perfectly and does all the latest
stuff, the hobby is over. Not likely. Long live homebuilding!