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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

 

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 & 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?
  • 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

ANCIENT MODULATION

 

  • 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

 

 

http://www.antentop.org/

Page 77

 

74 75 76 77

 

 

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August 7, 2016 20:08

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