-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!
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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
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