Radio and Signals Fundamentals

Radio and Signals Fundamentals
Chapter 2 Radio and Signals Fundamentals

Radio and Signal Fundamentals Radio Signals and Waves
Signals travel back and forth between radios carrying voices, data and Morse code. Radio waves that travel at the speed of light. Radio waves start as an electrical signal in an antenna that constantly changes direction. The rate of change determines the signal’s frequency. The radio wave travels away from the antenna into space, vibrating or oscillating at the same frequency as the electrical signal. 4/19/2017 2010 Technician - Chapter 2

As the radio wave passes other antennas, it creates replicas of the original electrical signal. A radio converts the signal back into a voice, digital data or even Morse code. The process of turning the transmitter output signal into radio waves that leave the antenna is called “radiation” or “radiating”. The radio wave travels away from the antenna into space, vibrating or oscillating at the same frequency as the electrical signal. 4/19/2017 2010 Technician - Chapter 2

All radio equipment is designed to generate or manipulate radio signals. No matter how you communicate by ham radio --- with voice, Morse code or computer --- those resulting radio signals are usually referred to as just signals. 4/19/2017 2010 Technician - Chapter 2

Prefix Symbol Multiplication Factor Tera T 1010 1,000,000,000,000.0 Giga G 109 1,000,000,000.0 (One billion) Mega M 106 1,000,000.0 (One million) Kilo k 103 1,000.0 (One thousand) Hecto h 102 100 Deca (Basic unit) da 101 10.0 Deci d 10-1 0.1 Centi c 10-2 0.01 (One hundredth) Milli m 10-3 0.001 (One thousandth) Micro u 10-6 (One millionth) Nano n 10-9 (One billionth) Pico p 10-12 (One trillionth) 4/19/2017 2010 Technician - Chapter 2

As frequency increases, it becomes easier to use units of--- kilohertz (1kHz = 1,000 Hz) megahertz (1 MHz = 1,000 kHz or 1,000,000 Hz) and gigahertz (1 GHz = 1,000 MHz or 1,000,000,000 Hz) 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System 1.5 amperes = How many Milliamperes? 1,500 milliamperes 1.5 x 1,000 = 1,500 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System 1,500,000 hertz can be specified in what other ways? 1,500 kilohertz or 1.5 Megahertz 1,500,000 divided by 1,000 = 1500 kHz 1,500,000 divided by 1,000,000 = 1.5 MHz 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System How many volts equal a kilovolt? 1,000 volts Kilo = volt x 1,000 = a kilovolt 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System How many volts equal a microvolt? A millionth of a volt Micro = 1,000, volt ÷ 1,000,000 = a millionth of a volt 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System 500 milliwatts is equal to what? 0.5 Watts or one-half watt milli equals one thousandth 500 milliwatts ÷ 1000 = 0.5 watts 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System If an ammeter calibrated in amperes is used to measure a 3000-milliampere circuit what would be the reading? 3 amperes Milli = 1000 3000 mA ÷ 1000 = 3 amperes or “amps” or 0.003 A x 1000 = 3 amps 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System 3.525 MHz = How many kilohertz? 3525 kilohertz Kilo = 1000 3.525 x 1000 = 3525 kHz 4/19/2017 2010 Technician - Chapter 2

Metric conversions within the Metric System How many microfarads equal 1,000,000 picofarads? 1 microfarad A microfarad = one millionth of a farad 1,000,000 picofarads ÷ 1,000,000 = 1 microfarad 4/19/2017 2010 Technician - Chapter 2

As the signal oscillates, each back-and-forth sequence is called a cycle. The number of cycles per second is the signal’s frequency and is represented by the lower case “f”. The unit of measure for frequency is hertz, which is abbreviated as “Hz”. One cycle per second is one hertz or 1 Hz. 1 Second 4 Hertz or 4 Hz 4/19/2017 2010 Technician - Chapter 2

The strength or amplitude of a radio signal oscillates like a sine wave. One Cycle + time - One Wavelength 4/19/2017 2010 Technician - Chapter 2 One Second

The period of the cycle (represented by “T”) is its duration. The reciprocal of the period, 1/T, is the signal’s frequency, “f”. A harmonic is a signal with a frequency that is some integer multiple (2,3,4 and so on) of a fundamental frequency. 7.006 MHz = fundamental frequency MHz = second harmonic MHz = third harmonic MHz = fourth harmonic There is no “First Harmonic” 4/19/2017 2010 Technician - Chapter 2

Harmonic are used to shift signal frequencies and create new signals by radio designers. These unwanted signals can also cause problems such as interference and can potentially result in signals being transmitted outside the amateur frequency bands as “spurious emissions”. 4/19/2017 2010 Technician - Chapter 2

Every cycle of the signal has the same basic shape: Rising and falling and returning to where it started. Position within a cycle is called “phase”. Phase is used to compare how sine wave signals are aligned in time. Phase is measured in degrees and there are 360 degrees in one cycle of a sine wave. 4/19/2017 2010 Technician - Chapter 2

Two sine waves with a phase difference of 180 degrees so that one wave is increasing while the other is decreasing, they are “out of phase”. Waves with no phase difference (e.g., increasing and decreasing at the same time) are “in phase”. 4/19/2017 2010 Technician - Chapter 2

James Clerk Maxwell predicted the existence of radio waves in 1864. Heinrich Hertz was the first to send and receive radio waves in 1886. 4/19/2017 2010 Technician - Chapter 2

Signals below 20 kHz produce sound waves that humans can hear when connected to a speaker or headset. We call them audio frequency or AF signals. Signals whose frequency is greater than 20,000 Hz or 20 kHz are called radio frequency or RF signals. The range of frequencies of RF signals is called the radio spectrum. It starts at 20 kHz and goes through several hundred GHz or a thousand million times higher. 4/19/2017 2010 Technician - Chapter 2

For convenience, the radio spectrum is divided into ranges of frequencies that have similar characteristics. Frequencies above 1 GHz are generally considered to be microwaves. Microwave ov ens operate at 2.4 GHz Hams primarily use frequencies in the Middle Frequency (MF) through Ultra High Frequency (UHF) and microwave ranges. 4/19/2017 2010 Technician - Chapter 2

RF Spectrum Ranges Range Name Abbreviation Frequency Range Very Low Frequency VLF 3 kHz-30 kHz Low Frequency LF 30 kHz – 300 kHz Medium Frequency MF 300 kHz – 3 MHz High Frequency HF 3 MHz – 30 MHz Very High Frequency VHF 30 MHz – 300 MHz Ultra High Frequency UHF 300 MHz – 3 GHz Super High Frequency SHF 3 GHz – 30 GHz Extremely High Frequency EHF 30 GHz – 300 GHz 4/19/2017 2010 Technician - Chapter 2

Specific ranges of frequencies in which signals are used for a common purpose or share similar characteristics are called “bands”. The AM broadcast band covers kHz The FM broadcast band covers MHZ Frequency bands used by radio amateurs are called “amateur bands” or “ham bands”. 4/19/2017 2010 Technician - Chapter 2

FM Mobile Phones VHF TV UHF TV AM Shortwave VLF LF MF HF VHF UHF SHF EHF 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 300 GHz audio radio Some amateur portions of the RF spectrum Low Frequencies Long Wavelengths High Frequencies Short Wavelengths 4/19/2017 2010 Technician - Chapter 2

The “wavelength” of a signal is the distance that it travels in during one complete cycle. It is represented by the Greek letter lambda: All radio waves travel at the speed of light which is represented by a lower-case “c”. The speed of light in space and air is 300 million meters per second or 3 x 108 meters per second. 4/19/2017 2010 Technician - Chapter 2

Radio waves are often referred to by their wavelength or frequency because the two are related by the speed of light. You can determine the wavelength or frequency using these formulas: Wavelength = speed of light divided by frequency Frequency = speed of light divided by wavelength 4/19/2017 2010 Technician - Chapter 2

There are two important relationships between frequency and wavelength: As frequency increases, wavelength decreases As wavelength increases, frequency decreases It is very common to refer to frequencies in the amateur bands by their wavelength as well as their frequency. “I’ll call you on 2 meters. Let’s try MHz” 4/19/2017 2010 Technician - Chapter 2

“I’ll call you on 2 meters. Let’s try MHz” In the example above, the frequency band is referred to as “2 meters” because that is approximately how long the radio waves are in that band. (in meters) = 300 f in MHz 300 f (in MHz) = (in meters) 4/19/2017 2010 Technician - Chapter 2

“I’ll call you on 2 meters. Let’s try MHz” Determine the approximate wavelength: = 2.04 meters 300 MHz Determine the approximate frequency: 300 = 150 MHz 2 meters 4/19/2017 2010 Technician - Chapter 2

Determine the approximate wavelength: 300 MHz = meters Determine the approximate frequency: 300 = 15.0 MHz 20 meters 4/19/2017 2010 Technician - Chapter 2

Radio and Signal Fundamentals
Modulation Understanding the basic concept of modulation is very important to understanding the various techniques that radio amateurs use to communicate. A simple radio signal in and of itself isn’t very useful and doesn’t do much communicating. Information must be added or contained in the radio signal. The simplest radio signal at one frequency whose strength never changes is called a “continuous wave” which we abbreviate as “CW”. 4/19/2017 2010 Technician - Chapter 2

Modulation Adding information to a signal by modifying in some manner is called “modulation” Recovering information from a signal is called “demodulation”. The simplest type of modulation is a continuous wave that is turned on and off in a specified and distinct pattern such as Morse code. Morse code radio signals are often referred to as “CW” for that reason. 4/19/2017 2010 Technician - Chapter 2

Modulation If we add speech to the radio signal, the result is a “phone” or “voice” mode signal. If data is added to the radio signal, the result is a “data mode” or “digital” mode signal. Analog modes carry information that can be understood directly by a human such as speech or Morse code. Digital or data modes carry information as data characters between two computers. Software in the computers converts the information into a readable form as text or pictures. 4/19/2017 2010 Technician - Chapter 2

Modulation Three characteristics of a signal can be modulated: It’s amplitude or strength It’s frequency It’s phase All three types of modulation are used in ham radio. 4/19/2017 2010 Technician - Chapter 2

Modulation You’re probably familiar with two types of modulation: Amplitude modulation or “AM” Frequency modulation or “FM” You probably never gave it any thought about it but are familiar with these to modulations from you car radio or home stereo system. Hams use variations of AM and FM plus many more types of modulation. 4/19/2017 2010 Technician - Chapter 2

Modulation Amplitude Modulation Turning an unmodulated signal on and off can produce Morse code characters. Adding speech to an unmodulated signal will cause it’s amplitude or strength to vary. The information is contained in the “envelope” of the resulting signal. 4/19/2017 2010 Technician - Chapter 2

Modulation The receiver recovers your voice by following the signal’s amplitude variations. This process of recovering speech or music in an AM signal is called “detection” and can be performed by very simple circuits. AM is used because it is simple to transmit and receive. 4/19/2017 2010 Technician - Chapter 2

Modulation An AM signal is composed of a carrier and two sidebands. The total power of an AM signal is divided between the carrier and two sidebands. The carrier is a continuous wave whose amplitude does not change and does not contain any information. 4/19/2017 2010 Technician - Chapter 2

Modulation The “upper sideband” or “USB” is higher in frequency than the carrier tone. The “lower sideband” or “LSB” is lower in frequency than the carrier. 4/19/2017 2010 Technician - Chapter 2

Modulation If the AM signal had a carrier of 800 KHz modulated by a single steady tone of 600 Hz, it would result in two sidebands each of whose width would be 600 Hz each. Both sidebands contain the information needed to reproduce the tone used to modulate the signal. 800 kHz 799.4 kHz 800.6 kHz 600 Hz 600 Hz 4/19/2017 2010 Technician - Chapter 2

Modulation The addition of sidebands during the process of modulation causes the resulting modulated signal to be spread over a range of frequencies called the signal’s “bandwidth”. Each signal has some bandwidth. A simple CW signal requires a bandwidth of up to 150 Hz. 600 Hz 600 Hz 1200 Hz bandwidth 4/19/2017 2010 Technician - Chapter 2

Modulation Single-Sideband (SSB) AM signals are inefficient from the standpoint of power. The carrier doesn’t contain information yet it takes up most of the signal power. Each sideband contains an exact copy of the modulated signal. A single-sideband signal is an AM signal with the carrier and one sideband removed so that all of the signal’s power is devoted to the remaining sideband. 4/19/2017 2010 Technician - Chapter 2

Modulation An AM signal with the carrier and one sideband removed by electronic circuitry is called a single sideband (SSB) signal. 4/19/2017 2010 Technician - Chapter 2

Modulation The upper sideband (USB) is used on VHF and UHF. Both USB and LSB are used on the MF and HF bands SSB signals require more complex equipment but the improved performance is worth it. SSB signals have a superior range because all of the power is concentrated in a single sideband. The SSB’s bandwidth is less than 3 kHz 4/19/2017 2010 Technician - Chapter 2

Modulation Frequency & Phase Modulation Modes that vary the frequency of a signal to add speech or data information are called frequency modulated or FM signals. Each cycle of the unmodulated carrier is the same. The signal of a frequency modulated carrier increases and decreases as the amplitude of the signal changes. 4/19/2017 2010 Technician - Chapter 2

Modulation The frequency of an FM signal varies with the amplitude (strength) of the modulating signal. The amount of variation is called “carrier deviation” or just “deviation”. Speaking louder into the microphone of an FM transmitter increases deviation. As deviation increases, so does the signal’s bandwidth. Excessive deviation can cause interference to nearby signals. 4/19/2017 2010 Technician - Chapter 2

Modulation Your radio displays only the carrier frequency. You must remember to leave room the signal’s sidebands. You do not want to transmit out of the amateur bands or outside of you frequency privileges. That’s illegal. If your FM voice signal is 15kHz wide, that means the sideband is the center frequency plus 7.5 kHz. Frequency. Give yourself a 10 kHz margin to be safe. 4/19/2017 2010 Technician - Chapter 2

Modulation Phase Modulation Phase modulation or PM is similar to FM. Phase modulation varies the phase instead of the frequency. These two techniques result in signals that are approximately the same. Receivers demodulate the FM and PM signals with the same circuit. 4/19/2017 2010 Technician - Chapter 2

Modulation Phase Modulation Most hams refer to either FM or PM signals as FM FM signals have one carrier and many sidebands that add together in a 5-15 kHz bandwidth. The amplitude of a FM signal does not change 4/19/2017 2010 Technician - Chapter 2

Modulation What are the different types of modulation and signals available? How do you choose one over the other? What are the strengths and weaknesses of each What makes on better than another? 4/19/2017 2010 Technician - Chapter 2

Modulation Fortunately, there has been a lot of experimenting since ham radio began – it’s sorta what we do. Why use FM for VHF and UHF voice if these signals occupy more bandwidth than SSB? The information in an FM signal is carried as variations in the signal’s frequency. Atmospheric and electrical noises are meaningless to an FM signal. The limiter circuit in an FM receiver strips away the noises so they are not heard in the receiver’s output. 4/19/2017 2010 Technician - Chapter 2

Modulation Unfortunately, the AM signals are subject to all the noise while the FM signals are static-free. For short-range and regional communications, the lower noise of FM signals clearly outweigh any considerations about bandwidth. FM can also be used for data signals, such as those for “packet radio” on VHF and UHF. 4/19/2017 2010 Technician - Chapter 2

Modulation Even though FM may proved a better quality signal, SSB is often used where signals are weaker and where the spectrum will not support a large number of FM users. Signals on the HF bands below 30 MHz are almost exclusively SSB or CW. SSB signals use much less bandwidth than FM or digital signals. 4/19/2017 2010 Technician - Chapter 2

Radio and Signal Fundamentals Typical Signal Bandwidths
Modulation Typical Signal Bandwidths Type of Signal Typical Bandwidth AM amateur voice 6 KHz Amateur television 6 MHz Commercial television 6-7.5 MHz SSB voice 2-3 kHz SSB digital 500 to 3,000 Hz (0.5 to 3 kHz) CW Hz (0.1 to 0.3 kHz) FM amateur voice 5-15 kHz Commercial FM 150 kHz 4/19/2017 2010 Technician - Chapter 2

Radio and Signal Fundamentals CW ops rule. Phone ops drool.
Modulation Because the signal’s power is concentrated into a narrow bandwidth, it is possible to communicate over much longer distances and in poorer conditions compared to FM or AM, particularly on the VHF and UHF bands. That’s why the VHF and UHF “Dxers” and contest operators use SSB. For even better range, extremely narrow CW signals are the easiest for a human operator to send and receive, especially in noisy or fading conditions. CW ops rule. Phone ops drool. 4/19/2017 2010 Technician - Chapter 2

Modulation Upper sideband or lower sideband – which to use? It doesn’t matter as long as both stations are using the same sideband. Otherwise it won’t work. Ham radio operators and manufacturers have agreed upon a standard: Above 10 MHz – USB is used including all of the VHF and UHF bands. Below 10 MHz – LSB is used EXCEPT on the 60m band where you are REQUIRED to use USB. 4/19/2017 2010 Technician - Chapter 2

Radio and Signal Fundamentals Radio Equipment Basics
The basic elements of a radio station Transmitter (Xmtr) – Generates/converts sounds into a signal that carries speech, Morse code or data information. Receiver (Rcvr) – Recovers/converts speech, Morse code or data information. 4/19/2017 2010 Technician - Chapter 2

Three basic elements of a radio station 3. Antenna (Ant) – Turns radio signals into energy that travels through space as a radio wave. The antenna also captures radio waves and turns them into signals for the receiver to work with. A feed line connects the antenna to the transmitter or the receiver. 4/19/2017 2010 Technician - Chapter 2

Most amateur equipment combine the transmitter and receiver into a single piece of equipment called a transceiver (XCVR). This is normally what hams mean when they refer to something as a radio or “rig”. A transceiver shares a single antenna between the transmitter and receiver by using a transmit-receive (TR) switch. 4/19/2017 2010 Technician - Chapter 2

4/19/2017 2010 Technician - Chapter 2

Antenna The operator would have to switch the antenna back and forth between transmitting and receiving. Feed Line (Coax) Transmitter Antenna T/R Switch Receiver Power Supply AC Outlet 4/19/2017 2010 Technician - Chapter 2

Antenna 1 Antenna 2 Power Supply Feed Line (Coax) AC Outlet Transceiver Receiver Transmitter Antenna Switch (Internal/external) Antenna Tuner 4/19/2017 2010 Technician - Chapter 2

Antenna Feed Line 450 Ohm “ladder Line” Antenna Tuner SWR/Power Meters Speaker Receiver Transmitter Morse Code Key 4/19/2017 2010 Technician - Chapter 2

A repeater is a station that transmits a received signal simultaneously on another frequency or channel. Repeaters provide local and regional communications between low-power mobile and portable stations. The job of the repeater is to provide a strong, low-noise signal that everyone can hear and understand well, especially during emergencies. 4/19/2017 2010 Technician - Chapter 2

A repeater consists of a receiver and transmitter connected together so that the received signal is retransmitted on a different channel or even multiple channels. Because a repeater receives and transmits at the same time, it uses a duplexer instead of a transmit-receive switch. The duplexer allows the strong signal from the transmitter and the weaker signals being received to share a single antenna. 4/19/2017 2010 Technician - Chapter 2

A simple repeater Receiver Transmitter Duplexer Received signal in Transmitted signal out Speech from received signal 4/19/2017 2010 Technician - Chapter 2

Input Freq MHz Output Freq MHz Offset + 600 kHz 50-60 miles Listen on MHz Transmit on MHz 4/19/2017 2010 Technician - Chapter 2

Accessories 4/19/2017 2010 Technician - Chapter 2

Amplifier Desk Microphone Headphones with Microphone Terminal Node Controller 4/19/2017 Morse code Paddles 2010 Technician - Chapter 2

Straight Key Dummy Load Speaker Antenna tuner 4/19/2017 2010 Technician - Chapter 2 Computer

A microphone or “mike” converts sound waves into an electrical audio signal and connects to the transmitter (or transceiver) A speaker turns an electrical audio signal into sound waves. Headphones are often used in place of a speaker to help you hear in a noisy area or when dealing with interference. 4/19/2017 2010 Technician - Chapter 2

An amplifier are circuits or equipment that increase the strength of a signal. Preamplifiers increase the strength of a signal before it is heard in the receiver. Power amplifiers increase the strength of a transmitted signal before it is sent to the antenna. A Morse key is a special “switch” used by the operator to turn the transmitter’s output signal on and off in the pattern of Morse code. 4/19/2017 2010 Technician - Chapter 2

Questions? Radio and Signal Fundamentals Radio Equipment Basics
Read chapter 3 for next week 4/19/2017 2010 Technician - Chapter 2

Radio and Signals Fundamentals

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