Class 2

1. Class 2 et198B

2. ET 198BCommercial and Amateur (Ham) RadioFCC license Preparation Course. Bill Croghan WB0KSW PG-15-6818

3. How Radio Works! • The electromagnetic spectrum Spectrum refers to a range of energy that we are able to utilize, observe and measure. For our purposes, let’s use the Frequency of Vibration of something as our unit of Measure.

4. Electro magnetic spectrum • Spectrum could refer to light, but we are interested in that portion of the spectrum where electromagnetic energy exists. • Electro magnetic refers to magnetic forces produced by electricity. • Electricity is the motion of electrons, one of the building blocks of all matter.

5. One view of the Spectrum

6. Another View of the Spectrum

7. Still Another View

8. Electricity • Every atom of matter consists of particles. We picture the atom like the sun and the planets. The part in the middle is not directly relevant to our discussion, but the orbiting planets” are. These planets are called Electrons and their motion and the energy they produce is Electricity.

9. Electricity continued • Electricity is a force, The amplitude of the push of the electrons is also called Electro Motive Force or VOLTS. • The quantity of the force, that is the number of electrons moving, is called the Current. • We’ll cover this in greater depth in a couple of weeks.

10. Magnetic / Electric Fields • A simple magnet produces a field, that is constant. The Earth has a magnetic field that can be measured and detected with a compass and with more sophisticated instruments.

11. Waves • Some Waves

13. Nature of radio waves • Radio waves are Electromagnetic disturbances in the existing magnetic fields that are found through out the universe. We disturb those fields in an organized way for our purposes but sometimes the fields are disturbed by nature or man for other than useful purposes.

14. Nature of radio waves Lightning produces strong disturbances of the magnetic fields. Lightning is Electric in nature, thus the disturbances of the magnetic field Is energy found in the Electro magnetic spectrum. We call it noise! Noise is also produced by man made disturbances, i.e. electric motors, spark plugs, neon lights, accidental arcing of all types and Electro welding.

15. Wave length / Frequency • We observe the disturbances at various points through out the spectrum by looking at the Wavelength / frequency of the energy. The most common form of man made electro magnetic field that is useful is in the form of a sine wave.

17. AC Sine wave / hertz • Define Alternating current as electrical energy that flows first in one direction, then in another. This is illustrated by seeing the amplitude increase in the positive direction then pass through zero and increase in the negative direction. Use a skip rope to see what a wave looks like

18. Measuring AC by frequency • The unit of measurement for AC frequency is the Hertz. 1 Hertz equals one Cycle per second. • One cycle is the time a wave needs to go through a complete pattern. • Kilohertz = thousand Hertz 1,000 • Megahertz = million Hertz 1,000,000 • Gigahertz = billion Hertz.1,000,000,000

19. DEMONSTRATION • I’LL SHOW YOU A SIGN WAVE ON THE OSCILLOSCOPE. The O’scope display shows time vs. amplitude. Time on the horizontal axis, amplitude on the vertical. • Demonstration… put a sine wave of about 1000 Hz into the O'scope and connect it also to a speaker so it can be heard.

20. Demonstration continued • Show the peaks, zero crossing points positive and negative relationships and discuss the average, mean and RMS values of the sign wave. • While listening and looking observe the relationship between frequency and wavelength.

21. Frequency and wavelength are inversely related • As Frequency increases, wavelength decreases. This is an absolute relationship. • Wavelength is however dependent on the velocity of the wave in the medium, i.e. free space, transmission line, etc.

23. Wavelength is equal to speed of light / frequency (times the velocity factor) (300 / F in MHz) x VF = wavelength in meters

24. Audio and Radio Frequency • The human ear can respond to frequencies ranging from 20 Hz to 20,000 Hz at best. • Audible sounds are a vibration of a substance • Radio waves can range from near DC to extremely high, but are a vibration (disturbance) in a magnetic field.

25. Frequency bands • The bands of frequencies we are usually interested in as Ham operators are; • MF = .3 – 3 MHz • HF = 3 – 30 MHz • VHF = 30 – 300 MHz • UHF = 300 – 3000 MHz (3GHz) • We have many bands above 3 GHz, but these are largely experimental.

26. Amateur Frequencies • Ham radio operators have privileges on the following wavelength bands. • HF; • 160 Meters = about 1.8 MHz • 80 Meters = about 3.8 MHz • 60 Meters = about 5 MHz • 40 Meters = about 7.1 MHz • 30 Meters = about 10 MHz • 20 Meters = about 14.2 MHz • 17 Meters = about 18.1 • 15 Meters = about 21 MHz • 12 Meters = about 24.9 MHz • 10 Meters = about 29.0 MHz

27. VHF – UHF amateur bandsAll available to no code technicians • 6 meters = About 52 MHz • 2 meters = about 146 MHz • 1 ¼ meters = About 222 MHz • 70 cm = about 445 MHz • 33 cm = about 915 MHz • 23 cm = about 1280 MHz • A number of higher Frequency bands, then all above 300 GHZ.

28. Types of Modulation • Emissions describes the method by which we impress intelligence on the radio signal. • Emission Designators will be used at the general level, but at the tech level we will talk about types by name. • The unmodulated signal with not information included is called a steady RF signal. It is usually a test signal

29. Intelligence carrying signals. • The first and simplest mode is to turn the transmitter on and off. This is called CW or continuous wave. The on off keying is done usually to the pattern of the Morse Code. • CW is the simplest to Transmit, and one of the most effective since it can cut through noise and be more easily copied at the receiving end.

30. Voice Modes • The most common modes used to transmit voice (or music) are AM, FM or Single Sideband. These are called PHONE modes under FCC rules and regulations. • There are digital modes used to transmit data, remote controls, telemetry, Packet Radio, Radio Teletype and other special purpose signals

31. The two signals that make up a radio wave

32. AM • AM stands for Amplitude Modulation. In AM, an audio signal is mixed with the Radio signal in such a fashion that it adds to and subtracts from the Amplitude of the RF signal. The result is known as Modulation. • The process also creates additional signals.

33. AM

34. AM sidebands • Mixing two signals usually results in additional signals. This process is called HETRODYNING. • When two signals mix, the end result is the original two, the sum and the difference. • Example. Mix and audio signal of 1000 HZ with a radio signal of 1,000,000 Hz (1 MHz) gives the following results.

35. Heterodyning • 1000 Hz Audio • 1,000,000 Hz RF • 1,001,000 Hz Upper Sideband • 999,000 Hz Lower Sideband • The added sidebands are included in the Increase and decrease of the amplitude of the AM signal.

36. Looking at it another way • 1,000 Hz audio tone • 1 MHz Radio frequency • 1.1 MHz upper sideband • .99 MHz Lower sideband • NOTE: the intelligence is the same in both sidebands. One is merely Higher in frequency than the original signal (Carrier) and the other is lower by the same amount.

37. Power distribution in the AM signal • A fully modulated AM signal will have the power distributed in the following way; • Original carrier will have 2/3 of the power • The sidebands will have 1/3 of the power; • Each sideband has 1/6th of the power. • Each sideband has all the information necessary to reproduce the signal at the receiver.

38. Let’s try an example • If we have a transmitter capable of 100 watts; • 66 Watts will be in the carrier • 33 Watts in the sidebands, or • 16.5 Watts in each • So the intelligence in a 100 watt signal is all riding on only 16.5 watts!

39. Lets try something • If we generate the full AM signal, then filter out the waste before amplifying it; • We can put the entire 100 watts into the single sideband. • Looking at an equivalent full AM signal, that would be like having two sidebands of 100 watts each and a carrier of 400 watts. • Our single sideband 100 watt signal is now the equivalent of a 600 watt AM signal!

40. BONUS • Since our Single Sideband signal now only takes up half as much space in the band, someone else can use the other half! We can get twice as many signals into the same bandwidth! • In the amateur service we usually use only one sideband either Upper or Lower depending on the band, but that’s just common practice. We could use either.

41. Another Bonus! • The single sideband is only generated when someone is talking. Thus during quieter periods, there is less power consumed. A loud voice will have a higher power output but a softer voice or pauses will have less. Power is thus more efficiently used. Batteries last longer, interference is less present, and equipment doesn’t heat up as much.

42. SSB uses • ON the HF amateur Bands, SSB is the most common voice mode. On 80 and 40 Meters, LSB is usually used, and on the other bands USB is most commonly used. • In commercial and military service, USB is the most common.

43. On the VHF and UHF bands,FM is the most common voice mode • FM is frequency modulation. • Instead of using the audio signal to vary the Amplitude of the signal, we use it to vary the Frequency of the signal. • Since Noise is usually Amplitude in nature, FM is quieter. • FM typically takes a wider chunk of the band width for a given application.

44. FM

45. Other FM characteristics • The Amplitude of FM is constant, since only the frequency is varied, there is no change in power with modulation, thus none of the advantages of SSB. • Most commercial two way radios in the VHF and UHF range use FM because of the noise immunity. • Newer radios are using narrower bandwidth FM due to improvements in the technology.

46. Some FM terms • Full Quieting. Used to indicate that the signal is strong enough to eliminate all the noise at the receiver. • Capture. When two signals of different strengths hit an FM receiver, the stronger one will be the only one heard if it is significantly stronger than the other.

47. Some of the Digital Modes • RTTY Short for Radio Teletype Telegraphy. The original Teletype. In the past used large clunky typewriter type devices to transmit text. Now most RTTY signals are sent from and to computers. • Packet Radio A modern data transmission system similar to the way messages are sent over the internet, only using radio waves.

48. RTTY and Packet modulation • Both of these modes use conventional Phone modulation schemes, i.e. FM, or SSB. On HF, typically SSB, and on VHF and UHF, the use FM. • At HF frequencies, they shift rapidly between two RF freqs to represent the digital states. This is known as FSK or Frequency Shift Keying.

49. The other method • In most cases, they send a digital signal by switching between two audio tones to indicate the two states of digital. This is known as AFSK or Audio Frequency Shift Keying. The AFSK signal is fed into the normal microphone input of the transmitter. In SSB mode the result is the same as FSK.

50. Advantages of digital modes • Both RTTY and Packet can result in rapidly sent text messages. • Packet can also send data files or other data information, i.e. digital pictures, computer programs or telemetry. • Packet further has the advantage of being able to Error correct, that is receive acknowledgment from the receiving station of correct reception and retry when it does not.