Special Modes and Techniques

1
Special Modes and Techniques

• Chapter 4 Section 6

2
Extending Communication Range with Satellites

• Higher VHF and UHF frequencies pass through the
  atmosphere without bouncing
• This makes them suitable for satellite contact
• You can use satellites like repeaters to talk to
  amateurs in other countries (T7B03)
• Any amateur whos license allows them to transmit
  on the satellites uplink frequency may use the
  satellite (T7B01)
• The group that has coordinated the building and
  launching of the largest number of amateur
  satellites is AMSAT (T7B08)
• Many amateur satellites are called LEOs which
  stands for Low Earth Orbit (T7B11)

3
Satellite Frequencies

• Band plans designate certain frequencies for
  satellite communication
• The Satellite Sub-band is the portion of the band
  where satellite operations are permitted (T7B09)
• The Satellite Sub-band for 70 cm is 435-438
  mghrtz (T7B10)

4
Special Satellite Problems

• Satellites are moving fast over the horizon
• One impact of moving is Doppler Shift
• A Doppler Shift is a change in signal frequency
  caused by movement through space (T7B07)
• Most common example is change in sound of a
  trains horn as it is coming and then passes
• Problem is that frequency to contact a satellite
  may not be the exact frequency it is suppose to
  uplink on
• Satellites send out Beacon Messages
• A satellite beacon is a signal then carries
  information about a satellite (T7B05)
• To determine when you can contact a satellite use
  a satellite tracking program (T7B06)
• As always when contacting a satellite you should
  use the minimum power needed to make the contact
  (T7B02)

5
Other Spacey Activities

• Amateur Radio can be used to contact the
  international space station
• Most of the time one or more of the astronauts
  are amateur operators
• Have to use programs to know when it will pass
  over
• Many people also use directional tracking
  antennas to confirm when range is just right
• Any amateur with a technician or higher class
  license can call the space station (T7B04)

6
Up in the Air About Other Things

• Radio controlled model planes use amateur radio
  frequencies
• To legally run them you need an amateur radio
  license
• The transmitter must be labeled with the licenses
  call sign and address (T7A12)
• The maximum amount of power allowed in
  transmitting control commands is 1 watt (T7A11)

7
Special Events and Contests

• Amateur radio may support a local event
• River to River relay run
• Parades
• A special event station is a temporary station
  that operates in conjunction with an event of
  special significance (T7A10)
• Often get a special event call sign to be used in
  conjunction with the event.
• They have contests to see who can contact the
  most stations in a given period of time
• An activity that involves contacting as many
  stations as possible is contesting (T7A07)

8
Fox Hunts

• Have a hidden transmitter or station and people
  have contest to see who can track it down first
• A directional antenna is the most useful device
  for finding a hidden transmitter (T7A06)
• Signal is strongest when you are aiming at the
  target
• If you get a direction from several positions the
  lines will cross at the transmitter location
• The method of radio direction finding can be used
  to locate sources of noise, interference or
  jamming (T7A05)
• People who pull stunts on amateur radio often
  dont fully realize that amateurs guard their
  privileges and often know how to track down
  violators

9
Where its At

• Operators may send out a signal with their
  location along with transmissions
• APRS stands for Automatic Position Reporting
  System (T6C02)
• Works on 144.39 Mghrtz
• You need a global positioning system receiver in
  addition to your radio to send out a location
  report (T6C03)

10
Digital Communication

• Oldest form is Morse Code simple, requires only
  operator skill, and telegraph key, get through
  interference and noise when voice cant
• One of the reasons to use digital communication
  instead of analog to communicate with another
  station is because many digital methods
  automatically correct for errors caused by noise
  or interference (T5D13)
• Packet Radio is an example of a digital
  communication method (T6C01)

11
Digital Modes

• PSK31 is a low speed data transmission mode that
  works well under noisy conditions (T6C07)
• PSK stands for Phase Shift Keying (T6C06)

12
Efficient Use of Spectrum

• Radio voice communication on FM uses about 15
  khrtz
• Digital transmissions can be in the 3 khrtz range
• Contrast with Analog Television Station
• NTSC refers to the US standard fast scan color
  television signal (T6C04)
• The Normal Bandwidth for a conventional fast scan
  television transmission is 6 Mhrtz (T6A11)
• That is 150 the size of the whole 2 meter
  amateur band