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ANTENTOP- 02- 2004, # 006  

Crystal Sets to Sideband


·       Using the BFO oscillator to match crystals

·       Switch in filters with a rotary switch

·       The IF amplifier

·       The cascode amplifier strip - variable gain with constant Q

·       Automatic Gain Control (AGC) - not a luxury

·       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

·       Bandswitching

·       Receiver power supplies

·       Use a linear regulator, not a switching regulator

 Chapter 14




  • How old can radio technology be and still be used on the air today?
  • Why bother with vacuum tubes?
  • Glowing filaments, colored plasmas & 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




  • It can’t be that hard! Want to bet?
  • 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 tranceivers
  • 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
  • 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 & not the usual low pass
  • Checking out the generator
  • Driving a 50 watt linear amplifier


Chapter 16



  • Defining amplitude modulation
  • Modulating vacuum tube final amplifiers
  • Plate, screen & cathode modulation
  • A "collector modulator"
  • Converting a MOSFET keyer into a modulator
  • Generating AM with an SSB balanced modulator
  • Compensating for non-linearity
  • Compression by accident
  • You probably don't need to build a compressor


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!

Thanks for reading my book.


73's Frank W. Harris, K0IYE

Page 77


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February 10, 2018 21:18

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