Electronic Direction Finding

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Electronic Direction Finding

• Developed as part of the National Emergency
  Services Curriculum Project

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How the Mission Starts

• ELT set off by plane crashing, or EPIRB goes off
  when ship sinks or when either is accidentally
  set off
• 97 to 99 percent of all ELT missions are false
  alarms
• SARSAT or COSPAS receives the signal
• The satellite transmits the mirror locations of
  the target to a Local User Terminal (LUT)

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How the Mission Starts Continued

• The LUT forwards the information to the Mission
  Control Center so that the appropriate Rescue
  Coordination Center can be notified
• AFRCC, at Langley AFB, calls the mission
  coordinator or designee who proceeds with the
  callout

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Rescue Coordination Centers (RCCs)

• Receive SARSAT Distress Alerts from the USMCC
• Coordinate the Rescue Response

U.S. Coast Guard Responsible for all Maritime
Alerts
U.S. Air Force Responsible for all Inland
Alerts
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United States Cospas-Sarsat Program
Administration
Inland SAR
Maritime SAR
Research Development
System Operation
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Distress Beacon Frequencies

• Primary
• 121.5 MHz, and its harmonics (243 MHz)
• 243 MHz, military frequency
• 406 MHz, next generation distress beacons
  transmitting location, tail number or boat
  identification, etc.

• Training
• 121.775 MHz
• Required by FAA as of 31 January 1998
• 121.6 MHz is no longer authorized for training

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Frequency Change

• SATELLITE PROCESSING OF 121.5/243 MHz EMERGENCY
  BEACONS TO BE TERMINATED ON FEB. 1, 2009
• Mariners, aviators, and individuals using
  emergency beacons will need to switch
  to those operating at 406 MHz if they want to be
  detected by satellites.

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Frequency Change Cont.
it becomes illegal for use on Jan 1st,
2007!!!
This is a new regulation under the recently
issued FCC Title 47, Part 80 rules (August, 2003)
Can no longer purchase a 121.5 MHz EPIRB as of
Feb 1st, 2003
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The Future of Cospas-Sarsat
The Distress Alerting Satellite System

• 406 MHz bent-pipe repeaters on future GPS
  satellites
• Full compatibility with existing future 406
  MHz beacons
• Continued global detection and location
• Greater than current Cospas-Sarsat accuracy
• Alert data downlink will continue to be freely
  available internationally
• Possible two-way return link

GPS Satellite
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The Bottom Line

• 2002 COSPAS-SARSAT Rescues
• 1,545 persons rescued in 365 SAR events
  worldwide
• - 1341 maritime rescues in 239 SAR events
• - 83 aviation rescues in 47 SAR events
• - 121 land rescues in 79 SAR events
• 2002 U.S. SARSAT Rescues
• 171 persons rescued in 69 SAR events nationwide
• 133 maritime rescues in 64 SAR events
• 11 aviation rescues in 5 SAR events
• 27 land rescues in 18 SAR events

Since 1982 over 15,000 lives rescued via
Cospas-Sarsat! Nearly 5,000 in U.S. AORs
alone!
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Distress Beacons

• There are three types of beacons used to transmit
  distress signals
• EPIRBs (for maritime use)
• ELTs (for aviation use)
• PLBs  (used for land-based applications)

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What are you looking for?
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Personal Locater Beacons

• In the United States, PLBs are now authorized for
  nationwide use. This authorization was granted
  by the FCC beginning July 1st, 2003.

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L-Per Components

• Receiver the actual metal box, has 7 features

• Dial indicates signal strength or direction
  depending on whether in REC or DF mode
• Mode switch sets into DF, REC or OFF positions
• Frequency selector allows the selection of the
  frequencies possible depending on what is
  installed and the model

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L-Per Components Continued

• Sensitivity switch a variable switch that
  adjusts the receiver's sensitivity. The closer
  to the target the less sensitivity is required
• Volume control adjusts the audible signal
• Speaker emits the audible signal
• Dial light switch turns the dial light on for
  use in low light conditions

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L-Per Receiver
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L-Per Components Continued

• Mast
• The two piece wooden vertical mast is joined in
  the middle by a bolt and wing nut, allowing the
  mast to be folded for storage or while the unit
  is carried through the woods.
• Make sure to hold the mast on both levels because
  the L-Per tends to be a knuckle-buster.

• The coaxial cable for connecting the radio to the
  antenna, and mounting screws for attaching the
  receiver to the mast are mounted to the mast.

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L-Per Components Continued

• Antenna crossbar
• Antenna elements are attached to the crossbar,
  varying in size according to the frequency that
  you are searching on
• Wire leads connect the antenna elements together
  at the switchbox located in the middle of the
  crossbar.
• The antenna elements fold down parallel to the
  crossbar for storage or carrying through the
  wilderness.

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Using the L-Per
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L-Per in DF Mode

• DF mode measures equal strengths of signal
• Not completely accurate, but good enough!
• When needle is centered, ELT could be either
  direction
• Needle always POINTS to the ELT (DFFollow the
  needle)
• Use a TURN to TELL if the ELT is in front or
  behind you

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DF Follow the Needle
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L-Per in REC Mode

• Receive Mode Measures Signal Strength only
• Signal comes from the direction of the arrows on
  the antenna (to your left)

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L-Per in REC Mode Continued

• Use it with multiple centers (more than 2) to
  verify strongest path
• Duel Reflections
• Thats most likely the true direction to the ELT

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Using the Tracker DF Unit
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Tracker Operating Instructions

• Unfold antennae of the receiver unit, front
  antennae first then rear antennae

• Start the receiver by pressing ON-button.
• When turning on the receiver, it will
  automatically select the international distress
  frequency (121.5 MHz), channel 1, and the green
  lights start blinking on the LED display
• Use the CH button switch between the distress and
  practice frequency

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Tracker Operating Instructions Continued

• By Pressing the MAN button you can choose manual
  operation instead of automatic.
• The MAN light will be lit when this mode has been
  selected
• Receiver sensitivity can be adjusted in the
  manual mode

• In manual or automatic mode, the LED display
  reflects signal strength in the direction of the
  signal beacon

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Sensitivity control when in manual mode
accomplished by rotating wheel
Signal strength indictor
Manual mode indicator light and low battery
indicator light
CH changes from channel 1 or 2 ?
Channel indicator lights
MAN switch alternates between automatic and
manual sensitivity
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Other Units

• There are other companies that produce electronic
  direction finding units.

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Body Shielding

• A method of beating reflections at close range
• Can use L-Per
• Radio Shack JETSTREAM radio is better and CHEAP!
• Body blocks out the signal
• Called a NULL
• Null should be at your BACK

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Body Shielding Continued

• At extremely close range, a 2m VHF radio
  un-squelched may work
• This works ok when trying to figure out a
  particular aircraft on a flight line, it will
  probably not identify a particular hangar

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Line of Sight Transmission

• ELTs are limited to Line of Sight propagation and
  reflections
• You dont always need to hear the ELT
• Carrier wave may be broadcasting with no audible
  sweep

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What Else Can Affect An ELT Signal?

• Power lines
• Fence Line (signal can follow)
• Reflections off of obstacles
• Hangars
• Moving Target
• Not using the Equipment Properly - See Picture at
  Right Whats wrong with this?

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Set Up the Equipment Completely
Open the Antennae Fully for use in the field
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Reflections

• To beat reflections

• Check sensitivity often
• Use REC mode
• Usually strongest signal is not a reflection
• Use the rubber ducky antenna when sensitivity is
  low
• Re-trace your steps if necessary, going back to
  locations of strong signal strength

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Triangulation

• Documenting team movements is logical, and can
  allow the team to locate the distress beacon
  sooner

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Triangulation Continued

• You must be able to receive the signal
• Center up DF unit on the signal
• Take the magnetic bearing (shoot an azimuth)
• Correct for magnetic variation
• East is least, West is best
• Plot your bearings (draw a line) on map
• The ELT should be where the lines cross!

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Plot your Bearings
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What information is needed for the IC?

• Make
• Model and Model
• Manufacturer
• Location Description
• Approximate location (Latitude Longitude)
• Owner
• Tail Number or Boat Name and Number
• Time Found and Time Shut-off

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What information is needed for the IC? Continued

• Switch Position on ELT or EPIRB ON, OFF, or ARM
• Manufacture Date
• Battery Expiration Date
• Information which could indicate reason for
  accidental or justified activation of ELT or
  EPIRB
• NOTE If you cant get certain information, dont
  worry, the AFRCC understands

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Electronic Direction Finding Tasks

• Ground Team Members
• O-0301 Determine Distress Beacon Bearing
• O-0302 Locate a Distress Beacon
• Ground Team Leaders
• O-0303 Deactivate a Distress Beacon
• O-0304 Triangulate on a Distress Beacon

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QUESTIONS?
THINK SAFETY!