Technician License Course Module Seven Radio and Electronics Fundamentals Signals and Waves

Radio Waves are AC You have already learned that in an alternating current (AC) the electrons flow in one direction one moment and then the opposite direction the next moment Radio waves (electromagnetic radiation) are AC waves Radio waves are used to carry the information you want to convey to someone else

Wave Vocabulary Before we study radio waves, we need to learn some wave vocabulary Amplitude Frequency Period Wavelength Harmonics Spend some time with live demonstration to make sure the students are really familiar with the concepts and vocabulary of waves. These demonstrations could include using audio frequency generator connected to a speaker and oscilloscope to allow students to hear a audio sine wave and see the wave. This will allow you to point out the differenced between amplitude and frequency, the relationship between frequency and wavelength, the relationship between frequency and period. 3

How Radio Waves Travel Moving electrons in the antenna create a magnetic field This changing magnetic field creates an electric field Then back and forth between magnetic and electric fields from point A to point B

Wavelength The distance a radio wave travels during one cycle One complete change between magnetic and electric fields This is the time to talk about the mathematical relationship between frequency and wavelength. Go over a few practice problems using examples of test questions. Give some problems for homework that are the test questions. 5

Finding where you are on the radio dial There are two ways to tell someone where to meet you on the radio dial (spectrum) Band Frequency

Radio Frequency (RF) Spectrum The RF Spectrum is the range of wave frequencies which will leave an antenna and travel through space The RF Spectrum is divided into segments of frequencies that basically have unique behavior Each segment division of frequencies will act the same, for instance, short range, reflect off similar surfaces, interact with the ionosphere the same way, etc. 7

Radio Frequency (RF) Spectrum Point out on the diagram where familiar signals are located like AM/FM commercial radio, police and fire channels, TV, satellite TV. Point out how each segment acts differently from adjacent segments. Don’t be afraid to tell them that it isn’t that simple, that the lines between segments sometimes are a little fuzzy, that is part of the fun of radio. 8

So, Where am I? Back to how to tell where you are in the spectrum Bands identify the segment of the spectrum where you will operate Wavelength is used to identify the band Frequencies identify specifically where you are within the band Give some real examples on how to articulate where to meet someone. I.e., I’ll be on 2 meters this evening, on a frequency of 146.52…see you there. Twenty meters is open to Europe today, listen for the rare station on frequency 14.175 MHz. 9

Another use for frequency and wavelength For the station antenna to efficiently send the radio wave out into space, the antenna must be designed for the specific operating frequency The antenna length needs to closely match the wavelength of the frequency to be used Any mismatch between antenna length and frequency wavelength will result in radio frequency energy being reflected back to the transmitter, not going (being emitted) into space Note that this statement is a generalization and there are a million exceptions, just go with it for instructional purposes and point out that in the beginning, many over generalizations must be made to facilitate understanding. Once the student understands the basic concepts, then the true complexity of radio and in particular antenna theory can be explored. 10

Antennas are part capacitor – part inductor – part resistor Antennas actually have characteristics of capacitor, inductor, and resistor electronic components Capacitors and inductors, because they store energy in fields, react differently to AC current than DC current Special kind of resistance to the flow of AC – called reactance This is going to be a big jump for some students. The concepts of reactance and resonance is difficult for even the most experienced hams let alone the new ham. If your students appear to be struggling during the discussion, point out that your main goal is for them to have just a fundamental understanding of the concepts and the vocabulary involved here. 11

Resonance Because capacitors and inductors store energy in different ways, the stored energy can actually cancel each other under the right conditions Capacitors – electric field Inductors – magnetic field Cancelled current = no reactance, just leaving resistance

Resonant Antenna If an antenna is designed correctly, the capacitive reactance cancels the inductive reactance Theoretically, the resulting reactance is zero Leaving only resistance – meaning minimum impediment to the flow of the radio frequency currents flowing in the antenna and sending the radio wave into space Talk here about the design of the basic dipole antenna. Use the wavelength formula to calculate the length of a ¼ wave vertical for two meters and then compare that calculation to a commercially produced antenna. 13

Adding Information - Modulation Now that we now where we are in the RF spectrum and are sending a radio wave into space When we imprint some information on the radio wave, we modulate the wave Turn the wave on and off Voice AM and FM Data Different modulation techniques are called modes You now need to make the jump from the discussion of radio spectrum and antenna resonance to the concept of modulation. The important concept here is understanding that modulation is imprinting information on the carrier radio wave. There are different ways to do this imprinting, those different ways are called modes 14

Morse Code – on and off

Amplitude Modulation (AM) In AM, the amplitude of the carrier wave is modified in step with the waveform of the information (voice) The ARRL modulation board is an excellent resource that can be used to demonstrate the concept of modulation. This board uses amplitude modulation and demodulation circuits along with an oscilloscope to visually depict what happens during modulation. 16

Characteristics of voice Sound waves that make up your voice are complex mixture of multiple frequencies This complex mixture is made up of two bands that are mirror images The sub-bands are called sidebands

Single Sideband Modulation (SSB) Since voice is made up of identical mirror image sidebands We can improve efficiency of transmission by transmitting only one sideband and then reconstruct the missing sideband at the receiver

Frequency Modulation (FM) Instead of varying amplitude, if we vary the frequency in step with the information waveform – FM is produced Discuss the concept of deviation, the amount of frequency change from the center frequency determines the volume of the transmitted information (percent modulation). Discuss what happens if you over deviate. Also discuss that FM can also be produced by varying the phase of the carrier, but this it is hard to distinguish between PM and FM so it isn’t particularly important for the new ham. Here is a good place to talk about the advantages and disadvantages of the different forms of modulation. 19

Transmitting Data Data is made up of binary bits 1 and 0 On and off states Modems translate the data into a format capable modulating a carrier wave A terminal node controller (TNC) is a specialize modem used in ham radio There are many more kinds of modems developed as data transmission technology advances

VEC Question Pool Module Seven

T2B05 What determines the amount of deviation of an FM (as opposed to PM) signal? A. Both the frequency and amplitude of the modulating signal B. The frequency of the modulating signal C. The amplitude of the modulating signal D. The relative phase of the modulating signal and the carrier

T2B05 (C) What determines the amount of deviation of an FM (as opposed to PM) signal? A. Both the frequency and amplitude of the modulating signal B. The frequency of the modulating signal C. The amplitude of the modulating signal D. The relative phase of the modulating signal and the carrier

T2B06 What happens when the deviation of an FM transmitter is increased? A. Its signal occupies more bandwidth B. Its output power increases C. Its output power and bandwidth increases D. Asymmetric modulation occurs

T2B06 (A) What happens when the deviation of an FM transmitter is increased? A. Its signal occupies more bandwidth B. Its output power increases C. Its output power and bandwidth increases D. Asymmetric modulation occurs

T3A07 What type of wave carries radio signals between transmitting and receiving stations? A. Electromagnetic B. Electrostatic C. Surface acoustic D. Magnetostrictive

T3A07 (A) What type of wave carries radio signals between transmitting and receiving stations? A. Electromagnetic B. Electrostatic C. Surface acoustic D. Magnetostrictive

T3B01 What is the name for the distance a radio wave travels during one complete cycle? A. Wave speed B. Waveform C. Wavelength D. Wave spread

T3B01 (C) What is the name for the distance a radio wave travels during one complete cycle? A. Wave speed B. Waveform C. Wavelength D. Wave spread

T3B03 What are the two components of a radio wave? A. AC and DC B. Voltage and current C. Electric and magnetic fields D. Ionizing and non-ionizing radiation

T3B03 (C) What are the two components of a radio wave? A. AC and DC B. Voltage and current C. Electric and magnetic fields D. Ionizing and non-ionizing radiation

T3B04 How fast does a radio wave travel through free space? A. At the speed of light B. At the speed of sound C. Its speed is inversely proportional to its wavelength D. Its speed increases as the frequency increases

T3B04 (A) How fast does a radio wave travel through free space? A. At the speed of light B. At the speed of sound C. Its speed is inversely proportional to its wavelength D. Its speed increases as the frequency increases

T3B05 How does the wavelength of a radio wave relate to its frequency? A. The wavelength gets longer as the frequency increases B. The wavelength gets shorter as the frequency increases C. There is no relationship between wavelength and frequency D. The wavelength depends on the bandwidth of the signal

T3B05 (B) How does the wavelength of a radio wave relate to its frequency? A. The wavelength gets longer as the frequency increases B. The wavelength gets shorter as the frequency increases C. There is no relationship between wavelength and frequency D. The wavelength depends on the bandwidth of the signal

T3B06 What is the formula for converting frequency to approximate wavelength in meters? A. Wavelength in meters equals frequency in hertz multiplied by 300 B. Wavelength in meters equals frequency in hertz divided by 300 C. Wavelength in meters equals frequency in megahertz divided by 300 D. Wavelength in meters equals 300 divided by frequency in megahertz

T3B06 (D) What is the formula for converting frequency to approximate wavelength in meters? A. Wavelength in meters equals frequency in hertz multiplied by 300 B. Wavelength in meters equals frequency in hertz divided by 300 C. Wavelength in meters equals frequency in megahertz divided by 300 D. Wavelength in meters equals 300 divided by frequency in megahertz

T3B07 What property of radio waves is often used to identify the different frequency bands? A. The approximate wavelength B. The magnetic intensity of waves C. The time it takes for waves to travel one mile D. The voltage standing wave ratio of waves

T3B07 (A) What property of radio waves is often used to identify the different frequency bands? A. The approximate wavelength B. The magnetic intensity of waves C. The time it takes for waves to travel one mile D. The voltage standing wave ratio of waves

T3B08 What are the frequency limits of the VHF spectrum? A. 30 to 300 kHz B. 30 to 300 MHz C. 300 to 3000 kHz D. 300 to 3000 MHz

T3B08 (B) What are the frequency limits of the VHF spectrum? A. 30 to 300 kHz B. 30 to 300 MHz C. 300 to 3000 kHz D. 300 to 3000 MHz

T3B09 What are the frequency limits of the UHF spectrum? A. 30 to 300 kHz B. 30 to 300 MHz C. 300 to 3000 kHz D. 300 to 3000 MHz

T3B09 (D) What are the frequency limits of the UHF spectrum? A. 30 to 300 kHz B. 30 to 300 MHz C. 300 to 3000 kHz D. 300 to 3000 MHz

T3B10 What frequency range is referred to as HF? A. 300 to 3000 MHz B. 30 to 300 MHz C. 3 to 30 MHz D. 300 to 3000 kHz

T3B10 (C) What frequency range is referred to as HF? A. 300 to 3000 MHz B. 30 to 300 MHz C. 3 to 30 MHz D. 300 to 3000 kHz

T3B11 What is the approximate velocity of a radio wave as it travels through free space? A. 3000 kilometers per second B. 300,000,000 meters per second C. 300,000 miles per hour D. 186,000 miles per hour

T3B11 (B) What is the approximate velocity of a radio wave as it travels through free space? A. 3000 kilometers per second B. 300,000,000 meters per second C. 300,000 miles per hour D. 186,000 miles per hour

T5A12 What term describes the number of times per second that an alternating current reverses direction? A. Pulse rate B. Speed C. Wavelength D. Frequency

T5A12 (D) What term describes the number of times per second that an alternating current reverses direction? A. Pulse rate B. Speed C. Wavelength D. Frequency

T5C05 What is the unit of frequency? A. Hertz B. Henry C. Farad D. Tesla

T5C05 (A) What is the unit of frequency? A. Hertz B. Henry C. Farad D. Tesla

T5C06 What does the abbreviation "RF" refer to? A. Radio frequency signals of all types B. The resonant frequency of a tuned circuit C. The real frequency transmitted as opposed to the apparent frequency D. Reflective force in antenna transmission lines

T5C06 (A) What does the abbreviation "RF" refer to? A. Radio frequency signals of all types B. The resonant frequency of a tuned circuit C. The real frequency transmitted as opposed to the apparent frequency D. Reflective force in antenna transmission lines

T5C07 What is a usual name for electromagnetic waves that travel through space? A. Gravity waves B. Sound waves C. Radio waves D. Pressure waves

T5C07 (C) What is a usual name for electromagnetic waves that travel through space? A. Gravity waves B. Sound waves C. Radio waves D. Pressure waves

T8A01 Which of the following is a form of amplitude modulation? A. Spread-spectrum B. Packet radio C. Single sideband D. Phase shift keying

T8A01 (C) Which of the following is a form of amplitude modulation? A. Spread-spectrum B. Packet radio C. Single sideband D. Phase shift keying

T8A02 What type of modulation is most commonly used for VHF packet radio transmissions? A. FM B. SSB C. AM D. Spread Spectrum

T8A02 (A) What type of modulation is most commonly used for VHF packet radio transmissions? A. FM B. SSB C. AM D. Spread Spectrum

T8A03 Which type of voice mode is most often used for long-distance (weak signal) contacts on the VHF and UHF bands? A. FM B. DRM C. SSB D. PM

T8A03 (C) Which type of voice mode is most often used for long-distance (weak signal) contacts on the VHF and UHF bands? A. FM B. DRM C. SSB D. PM

T8A04 Which type of modulation is most commonly used for VHF and UHF voice repeaters? A. AM B. SSB C. PSK D. FM

T8A04 (D) Which type of modulation is most commonly used for VHF and UHF voice repeaters? A. AM B. SSB C. PSK D. FM

T8A05 Which of the following types of emission has the narrowest bandwidth? A. FM voice B. SSB voice C. CW D. Slow-scan TV

T8A05 (C) Which of the following types of emission has the narrowest bandwidth? A. FM voice B. SSB voice C. CW D. Slow-scan TV

T8A06 Which sideband is normally used for 10 meter HF, VHF and UHF single-sideband communications? A. Upper sideband B. Lower sideband C. Suppressed sideband D. Inverted sideband

T8A06 (A) Which sideband is normally used for 10 meter HF, VHF and UHF single-sideband communications? A. Upper sideband B. Lower sideband C. Suppressed sideband D. Inverted sideband

T8A07 What is the primary advantage of single sideband over FM for voice transmissions? A. SSB signals are easier to tune B. SSB signals are less susceptible to interference C. SSB signals have narrower bandwidth D. All of these choices are correct

T8A07 (C) What is the primary advantage of single sideband over FM for voice transmissions? A. SSB signals are easier to tune B. SSB signals are less susceptible to interference C. SSB signals have narrower bandwidth D. All of these choices are correct

T8A08 What is the approximate bandwidth of a single sideband voice signal? A. 1 kHz B. 3 kHz C. 6 kHz D. 15 kHz

T8A08 (B) What is the approximate bandwidth of a single sideband voice signal? A. 1 kHz B. 3 kHz C. 6 kHz D. 15 kHz

T8A09 What is the approximate bandwidth of a VHF repeater FM phone signal? A. Less than 500 Hz B. About 150 kHz C. Between 10 and 15 kHz D. Between 50 and 125 kHz

T8A09 (C) What is the approximate bandwidth of a VHF repeater FM phone signal? A. Less than 500 Hz B. About 150 kHz C. Between 10 and 15 kHz D. Between 50 and 125 kHz

T8A10 What is the typical bandwidth of analog fast- scan TV transmissions on the 70 cm band? A. More than 10 MHz B. About 6 MHz C. About 3 MHz D. About 1 MHz

T8A10 (B) What is the typical bandwidth of analog fast- scan TV transmissions on the 70 cm band? A. More than 10 MHz B. About 6 MHz C. About 3 MHz D. About 1 MHz

T8A11 What is the approximate maximum bandwidth required to transmit a CW signal? A. 2.4 kHz B. 150 Hz C. 1000 Hz D. 15 kHz

T8A11 (B) What is the approximate maximum bandwidth required to transmit a CW signal? A. 2.4 kHz B. 150 Hz C. 1000 Hz D. 15 kHz

End Module Seven