Class 2

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Class 2

• et198B

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ET 198BCommercial and Amateur (Ham) RadioFCC
license Preparation Course.

• Bill Croghan
• WB0KSW
• PG-15-6818

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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, lets use the Frequency of Vibration of
something as our unit of Measure.
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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.

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One view of the Spectrum
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Another View of the Spectrum
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Still Another View
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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.

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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.
• Well cover this in greater depth in a couple of
  weeks.

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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.

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Waves

• Some Waves

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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.

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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.
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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.

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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

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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

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DEMONSTRATION

• ILL SHOW YOU A SIGN WAVE ON THE OSCILLOSCOPE.
  The Oscope 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.

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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.

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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.

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Wavelength is equal to speed of light /
frequency (times the velocity factor)

• (300 / F in MHz) x VF wavelength in meters

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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.

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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.

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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

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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.

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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

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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.

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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

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The two signals that make up a radio wave
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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.

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AM
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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.

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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.

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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.

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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.

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Lets 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!

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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!

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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 thats just common practice. We could
  use either.

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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
  doesnt heat up as much.

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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.

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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.

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FM
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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.

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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.

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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.

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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.

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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.

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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.

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PACKET RADIO

• Hams can take pride in the fact that Packet Radio
  was developed by Hams (In Tucson largely) and
  used developments also used by internet.
  Internet communications now have evolved using
  some of the developments that the Hams first
  used.

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Packet in Brief

• Computer based, the information is packaged into
  fixed length packets.
• They are bundled with some additional information
  that can indicate to the receiving station what
  the intended receiver should be, who sent it, and
  a check sum to determine if everything came
  through.

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Packet Continued

• The packet is then sent out and the receiving
  station receives it, decodes the information, and
  determines if it was received correctly. If so,
  it then sends back an acknowledgement packet and
  the sender knows its OK. If the sender does not
  receive the ACK, then it retries.
• Packets may be received out of order, but the
  receiving computer can reassemble them correctly
  from the information in the packet.

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More Packet

• The overhead information in a packet can also
  carry routing information. A packet can be sent
  via relays automatically, and the
  acknowledgements return via the same path.
• Packets can be sent unaddressed, so everyone can
  receive them, but then there is no error
  correction.

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Other Digital Modes

• There are some other more complex digital modes
  used in the amateur service that use various
  methods and have various advantages and
  disadvantages. Some of these are Amtor, Pactor,
  and PSK.

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Amateur TV

• There are two types of amateur TV used.
• Because of the tremendous bandwidth necessary to
  transmit a TV signal, on HF a technique called
  slow scan is used.
• On VHF, the method most commonly used is
  compatible with your home Analog TV sets. This
  is called fast scan TV.

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Slow Scan TV

• This system typically sends a single picture over
  a short period of time, similar to a FAX machine.
  It may take a full minute to transmit one
  picture in full color.
• This can be done in the same bandwidth as a
  conventional voice signal on HF, and that is the
  FCC requirement.

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Slow Scan continued

• The fast scan signal would be wider than any one
  HF allocation. Power would be spread over a much
  wider bandwidth, and thus would require more
  power to be effective.
• For the same reason, the pictures sent back from
  our space craft going far out are sent back slow
  scan to conserve batteries and be more efficient.

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Fast Scan TV

• Fast scan TV typically takes 6 MHz or more
  bandwidth. Thats wider than any amateur band
  including the 2 meter and 1 ¼ meter bands. Fast
  scan TV takes place on 440 MHz and higher. It is
  real time, normal TV usually compatible with your
  home TV and can be received on a home TV with
  simple adapters.

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TV modulation methods

• The modulation used for fast scan and slow scan
  TV is conventional AM, FM and SSB. The signals
  are converted from the camera to something that
  can modulate the transmitter, and then recovered
  at the receiver. For slow scan, a receiver that
  stores the picture is necessary.