Modulation Definitions Amplitude Size Frequency Rate of occurrence

Modulation

Definitions • • Amplitude: “Size” Frequency: “Rate of occurrence” Phase: “Position or interval within a cycle” Modulation: “To vary amplitude, frequency, or phase”

“Carrier” Pure Sine Wave (146 MHz, no info) Voltage or Current “Magical” NOT These Time or Distance

HF and VHF Carriers Voltage or Current Slow (HF, 80 m, 3 MHz) Fast (VHF, 2 m, 144 MHz) Time or Distance

Carrier/CW/AM “Carrier” Modulator or speech CW or OOK (BW=150 Hz) AM

AM vs. FM Single Audio Tone BWFM = 5 to 15 KHz

Sidebands AM SSB USB LSB DSB Note break in axis 3 KHz 28 MHz

SSB (BW = 3 KHz) Long Distance or Weak Signal 1. Two Tone Test Waveform 2. Compression Single Tone Test Waveform: “Splatter” Just a pure RF sinewave offset from carrier by audio tone frequency!! 3. This is how SSB speech sounds (tuned, AM detection, untuned) Sound clip: http: //www. hamuniverse. com/ssbinformation. html Photo: http: //users. tpg. com. au/users/ldbutler/Intermodulation. htm

Amateur TV • Analog fast-scan NTSC • Widest BW (6 MHz) • 440 MHz , 75 cm

Modulation Video Demos http: //hamelmer. com/Videos. html

Digital / Data Modes Fldigi Win. Pack FSK PSK Audio IN/OUT USB TNC/Sound Card

Digital / Data Modes • • • 219 to 220 MHz, also others Many different “flavors” “parity bit” extra bit detects errors BER = Bit Error Rate GPS can provide APRS

PSK 31 • Low Data Rate (Keyboard) • continuous whistle with a slight warble Sound files from http: //www. kb 9 ukd. com/digital/

MFSK • Shifts Audio Frequency between a number of different tones • Low data rate 64 bps • Sounds like a crazy bird Sound files from http: //www. kb 9 ukd. com/digital/

Packet • • • “High” Data Rate Checksum Header (Destination Call Sign) Automatic Repeat if error detected How it sounds: Sound files from http: //www. kb 9 ukd. com/digital/

Satellites AO-27 Mode V/U (J) FM Voice Uplink: 145. 8500 MHz FM (2 m) Downlink: 436. 7950 MHz FM (75 cm) SO-50

Satellite Info • 30+ operating satellites, including ISS • Any ham with privileges that allow transmitting on uplink frequency • Use minimum power necessary (as always) • Member contacted ham in England • U/V means UHF uplink, VHF downlink • V/U VHF up, UHF down

Satellite Orbits few hundred miles up Drawing http: //www. gma. org/surfing/sats. html 22, 237 miles up

Doppler Shift • LEO – Low Earth Orbit – Vs. Geostationary • 17, 000 mph! • Start by tuning receive freq HIGH by 15 KHz • End by tuning receive freq LOW by 15 KHz Sound file http: //www. exploratorium. com

Satellite Location • Get Pass Info from satellite tracking program, or • Get Pass Info from web (see screenshot above)

Satellite operation • Show up at correct time! • Steer beam antennas, tune radios for Doppler • Spin Fading due to rotation of satellite and antennas • Very short voice contacts – Callsign and Grid. Square (WA 1 QKT FN 32) • FM Packet commonly used digital mode

Radio Transceiver (and Amplifier)

Transceiver Block Diagram

CW/SSB Receiver Single-conversion superheterodyne receiver for CW/SSB 28 MHz CW/SSB RF signals Product Detector 455 KHz BP filtering for selectivity 500 Hz 455. 5 KHz 28. 455 MHz

FM Receiver (VHF/UHF) 146 MHz FM RF signals RF preamplifier Increases sensitivity Limiter Eliminates Any trace of AM 10. 7 MHz 135. 3 MHz Discriminator FM to Audio 1 KHz

CW Transmitter Oscillator

Other Equipment • Transverter – Transmitter frequency converter – Example: 28 MHz up to 222 MHz • RF Power Amplifier – 5 W up to 25 Watts (see satellite setup)

Antenna Measurements

Feedline and Load

SWR • • Standing Wave Ratio Zload = Zo (Feedline characteristic impedance) ? If Zload = Zline , SWR = 1, else SWR > 1: 1 Due to Reflections from load, and Constructive and Destructive interference “Standing Waves”

Acceptable “SWR”? • 1: 1 is perfect match • 2: 1 is fairly good, but transmitter may start to reduce power output • 4: 1 is poor, may stress parts, some power lost as HEAT in feedline, and transmitter will reduce power output

Antenna Tuner and SWR Meter Measures Impedance Ratio Impedance Transformer

SWR Meter 1. Forward, adjust Sensitivity to “SET” (Transmitting) 2. Reverse, read SWR (Transmitting)

Antenna Tuner Action Note that “SWR Meter”, when used with Antenna Tuner, Doesn’t actually measure SWR on feedline Measures Impedance Ratio Between Zload and design Z = 50 Ohms “SWR =1: 1” means Zload = 50 Ohms Transmitter is Happy, because it can deliver power to antenna system! Low SWR Here “Impedance Transformer” High SWR on feedline is still present and is usually OK

Dummy Load Use to prevent Radiation when Testing Transmitter (instead of using Antenna)

Safety

Handheld Radios (HTs) Generally safe as is –Low Battery Voltage, Enclosed –Low Power gives low RF exposure –Low Power gives low antenna voltage (16 Vrms)

RF Exposure • Non-Ionizing radiation • Hazard is said to be Tissue Heating • Microwaves – eyes most vulnerable

Maximum Permissible Exposure (MPE)

RF Exposure Duty Cycle

Thresholds for RF Evaluation Re-evaluate the station whenever an item of equipment is changed

To Reduce RF exposure: • • • Relocate antennas Reduce Power Change frequency band Change antenna radiation pattern Change antenna heading

Electrical Hazards

Electrical Hazards P=IV=IE 1. High V, Low I 2. Low V, High I 3. High V, High I

Human Body Model

Human Body Model A pair of copper wires was connected to a 120 V wall plug. The extreme danger of this was explained and then a hotdog was used to short-circuit the wires. The hotdog was cooked and then later eaten by a participant. DO NOT TRY THIS AT HOME!

Current in the Body

Shock Protection • 3 -wire cords with safety ground pin • Common ground for all equipment • GFI • Check voltage on large capacitors, discharge if necessary

Lightning

Lightning Protection • Disconnect Antennas • Ground Antennas • Do NOT operate with external antennas during thunderstorms • 8’ ground rods for each tower leg, short and direct connections to tower and each other, no sharp bends • Lightning protectors all to common plate

Fusing • Interrupts circuit in case of overload • Prevents fires • Place in series with AC “hot” conductor

Consequences of Improper Fusing

Large Batteries • • Vent explosive gas Don’t charge or discharge too quickly Can charge 12 V batteries from car Use a fuse!

Antenna Safety • >10’ from power lines • Mount out of reach (rf burns) • Climbing harness, safety glasses, gin pole

Troubleshooting & Repair

RFI Causes Radio Frequency Interference • Fundamental overload – clean, but very strong signals • Harmonics • Spurious Emissions

Curing your neighbor’s RFI • First, make sure your station is operating properly – If TVI – is your own TV receiving interference? • Ideal next step is to identify nature of “aggressor” and “victim” – f, location, etc. • Telephone – acts as radio receiver –add RF filter at telephone • RF filters – Snap-on ferrite chokes; Lowpass, Highpass, Bandpass, &Band-reject filters

If your neighbor’s Part 15 devices interfere with you • Work to identify offending device • Politely inform him that rules require him to stop usage if RFI occurs • Apply fixes at your station if practical

“Distorted or Noisy Audio” • • Off frequency Low batteries Bad location Hold radio “straight up”

“Garbled or Unintellegible Transmissions” • RF Feedback • FM: Over-deviation – talk farther away or, Under-deviation – speak up! • Noise or whine on mobile unit: interference from vehicle’s electrical system

Multimeter or DMM • • Voltage: Voltmeter - connect in parallel Current: Ammeter – connect in series Resistance: Ohmmeter – unpowered target Capacitor with Ohmmeter – reads low, then high

Soldering • • Use Rosin-core solder Use correct size iron and tip Be able to see joint clearly Apply heat to terminal, apply solder to terminal

Soldering tools

Bad Solder Joint (Cold Joint) Photo http: //www. aaroncake. net/

Bad Solder Joint (Cold Joint) Photo: Wikipedia

Broken and Good Joints Photo: Wikipedia