Transcript Casara ELT Homing

CASARA Ground ELT Homing
Module 4
Of
CASARA ELT Training Plan
Setting Up For Operation
Unfold
the four antenna
blades
 For optimum DF (Direction
Finding) accuracy set the
antenna blades in the 90º
position, as shown
Then fold open the handle
Return them to the stored
position in reverse order
(handle first, then antenna
blades)
Operation in the DF Mode
• To use the DF
• The receiver is held with the
arm extended and the
display screen at or above
eye level.
• This is VERY important for
best DF accuracy
Operation in the Receive Mode
• Press the “REC/DF” key
• The direction cross on the
display will be replaced
with the word “RECEIVE.”
• Buzz noise will disappear
• Hold the DF unit in the
operating position and turn
to where the strength bar is
tallest or the strength
number is largest.
• The signal source is now
off the left end of the
display as noted by the
arrows on the panel.
Radio Signal Propagation
1.
2.
3.
4.
Radio signals travel in a straight line.
Signals get stronger nearer the source and the rate or
change in signal strength is faster as you get closer.
Conductive objects reflect the radio signal. Objects such
as buildings, chain link fences, mountains, smooth
snowfields, grasslands and water, both block and reflect
the radio signal.
Stay as far away from power lines, metal buildings &
steep rock face cliffs as possible. The signal will bounce
off these and provide false directions.
Reflectors
• Near the ELT
– Blocks the signal in one direction
– Will still get good directional information because
the ELT and the reflector are close.
Building
ELT
Reflectors
• Near the Receiver
– Will see both a direct and a reflected signal.
– If the direct signal is not itself blocked or reflected,
it will be stronger.
ELT
Building
Reflectors
• Near the Receiver with main signal blocked
– Will see the reflected signal.
– Must follow the reflected signal till the receiver
can “See” the direct signal.
Building
ELT
Direction Bearing Reliability
• Circle check
–
–
–
–
Turn to face the signal
Turn slowly in a full circle
The needle or bar should center twice about 180˚ apart
If it centers more than twice or less than 120˚ apart, you
are getting reflected signals. This is not a good location
and bearings will not be accurate.
– Go to an unobstructed higher ground and get a
directional fix.
Direction Bearing Reliability
• Walking the baseline
– In DF mode walk toward the signal for 10 to 20 feet, while
watching the indicated direction.
– If the signal fluctuates back and forth by more than 60˚ this
is a poor site to work from. Move at least 200 feet ( 70
meters).
– If the swings are less than 120˚ you can continue walking
in the average direction, and while not precise it will take
you in the approximate correct direction.
– If the indicated direction remains constant (within 5
degrees) there are no reflections.
Procedures for homing
1.
2.
3.
4.
5.
6.
7.
8.
Take a bearing of the received signal.
Draw this line on your map.
Go to another unobstructed higher ground point roughly 30˚ to
60˚ off the line drawn on your map and take another directional
reading.
The intersection of these two points is roughly where the signal
is coming from. (barring false bounced signals).
Repeat one or more times to increase confidence in the location
of the ELT signal source.
Go to the point on the map where your lines intercept. Set up
and take another directional reading.
Look for roads and paths rather than walk though heavy brush.
Once you are very close (within a few meters), work in Receive
mode.
Direction finding inside buildings
• Due to the multiple reflections, Direction
indications are not useful.
• Switch to receive and watch the signal
strength. Ignore small variations within 10
feet as these are likely caused by
reflections. Proceed toward the strongest
signal.
Casara ELT Homing
Using Radio
Body Shielding and Off Tuning
Technique
Body Shielding
• Body Shielding is the best way to
beat reflections at close range
– Can use L-Per™
– At extremely close range, a VHF radio
unsquelched 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
How To DF by Body Shielding
• Your body blocks the signal when you turn
in a circle
– This is called a null
– The null should happen when the ELT is
directly to your back
Body Shielding Procedure
• Adjust the volume so you can hear the null
– If its too loud, you’ll never hear it get softer
– Consider leaving the volume in one position so you’ll be able to
tell if you’re getting closer
– Hold The Receiver Close to your Body
– Don’t let the antenna touch you
– Turn A Complete Circle
– When the ELT sweep gets louder, you’re closer!
– When its softer, the ELT is directly to your back!
Body Shield: The Null
SIGNAL
• No Signal To Your Receiver
– The Sound Gets Softer!
– The ELT Is Directly To Your Back
NULL!
ELT
Off-Frequency Tuning
• Off-Frequency tuning when:
• Sensitivity (L-Per™) is at the minimum and signal
is still too strong (full scale on receive)
• You don’t get a null during body shielding
Off-Frequency tuning may be used any time you have
too much signal, but this technique is especially
effective during body shielding
Closing remarks
• Keep notes
• Set the location format on
your GPS to degrees,
minutes and tenths of
minutes. The Military and
Casara work in these units.
• Set the Map Datum –
usually NAD 27.
Are there any questions?
CASARA
“THAT OTHERS MAY LIVE”
THANK YOU