Station Assembly, Practice and Safety

Introduction

Station Equipment — station equipment, power supplies, antennas, transmitters, receivers, and safety

Dummy Load — high-power resistor that dissipates RF energy as heat without radiating
Antenna Switch — selects between antenna, antenna tuner, or dummy load
Antenna Tuner — matches transmitter impedance to antenna impedance for maximum power transfer

Transformer — steps 120 VAC mains voltage up or down to desired level and provides isolation
Rectifier — diode circuit converts AC to pulsating DC in half-wave or full-wave bridge configuration
Filter Capacitor — large electrolytic capacitor smooths pulsating DC into flatter DC
Voltage Regulator — maintains steady 13.8 VDC output regardless of load current changes

Mobile Power — voltage drop, wire gauge, battery fusing, and direct-connection requirements

Yagi-Uda Antenna — reflector, driven element, and director on a boom provide directional gain

FM Transmit Chain — microphone to speech amplifier to modulator to oscillator to frequency multiplier to power amplifier
Deviation — frequency change caused by modulation; over-deviation causes splatter

CW Transmit Chain — oscillator to buffer to keying stage to power amplifier to antenna

AM Transmit Chain — microphone to speech amplifier to modulator to class C power amplifier to antenna

SSB Transmit Chain — microphone to speech amplifier to balanced modulator to SSB filter to linear amplifier to antenna
Microphone Gain — too high causes overmodulation and splatter; speech processor raises average level

AM Superheterodyne Receiver — RF amplifier to mixer to IF amplifier to AM detector to audio amplifier to speaker
Sensitivity and Selectivity — sensitivity renders weak signals; selectivity separates adjacent signals

SSB/CW Receive Chain — product detector and BFO re-insert the suppressed carrier

Chirp — frequency shift when key is pressed; caused by inadequate voltage regulation
Variable Frequency Oscillator (VFO) — tunable across the band without changing crystals
Amplitude Modulation — carrier amplitude varies with the modulating audio
Transmitter Efficiency — DC input power vs RF output power

Emission Bandwidths — CW is narrowest at 100 hertz, then RTTY, SSB, AM, and FM widest at 16 to 20 kilohertz

Electronic Keyer — generates uniformly timed dots and dashes; paddle controls dot and dash generation

Sound Card Interface — converts analog audio to digital data and back; connects computer to radio
Modern Digital Radio — can transmit voice, images, and data because modulation is software-defined
WSJT-X Suite — FT8, FT4, JT65, JT9 — weak-signal digital modes for HF
Winlink — global amateur email system via radio, works when internet is unavailable

Home Station Access — key-operated on/off switch in main power line prevents unauthorized use
High-voltage Power Supplies — interlock switch cuts power when cabinet is opened

Station Grounding — three distinct functions: AC safety, lightning protection, and RF bonding
Fuses — always use the correct rating; never bypass or replace with a higher-value fuse

Lightning Grounding — ground all antenna and rotator cables when station is not in use to direct surge energy to ground

RF Exposure Safety — Safety Code 6 regulates maximum exposure levels; 30 to 300 megahertz is highest risk range

Station Accessories — dummy load, antenna tuner, speech processor, and keyer for testing and optimisation
Power Supply — AC to 13.8 VDC chain; mobile wiring 10 AWG or heavier to limit voltage drop under 0.5 V
Antenna Types — vertical quarter-wave with ground plane, dipole half-wave centre-fed, Yagi with reflector and directors
Transmit Chain Comparison — FM, CW, AM, and SSB transmitter stages and their key differences
Receiver Comparison — FM limiter-discriminator, AM diode detector, SSB/CW product detector with BFO
Bandwidth and Keying — CW narrowest at 100 Hz to FM widest at 20 kHz; electronic keyers for clean Morse
Safety — access control, grounding, correct fuses, and lightning disconnection
RF Exposure — Safety Code 6 guidelines; 30 to 300 megahertz highest risk; eyes especially vulnerable