L-Per Direction Finding Modified from Hawk Mountain Civil

L-Per Direction Finding Modified from Hawk Mountain Civil Air Patrol 8 -APR-06

Objectives • • ELT Basics The Old Little L-Per DFing with the L-Per Hands-on Training

ELT Basics: The Flavors • ELT – Emergency Locator Transmitter – aircraft • EPIRB – Emergency Position Indicating Radio Beacon – boat • PLB – Personal Locator Beacon – hiker

ELT Basics: The Flavors • No matter what you call it… – Transmits on a distress frequency – Indicates the position of an emergency by means of direction finding or GPS – Can be manually or automatically activated • Throughout this session, ELT will be used generically to also include PLBs & EPIRBs

ELT Basics: The Frequencies • 121. 5 MHz – Civilian Emergency Aircraft Channel • 243. 0 MHz – Military Emergency Channel • 406 MHz – New Emergency Satellite Channel • ELTs can operate on just 1 or ANY combination of the above frequencies

ELT Basics: Training Frequencies • To practice, we have our own set of frequencies: – 121. 775 MHz – 121. 6 MHz (No Longer Authorized) – 243. 55 MHz (Proposed) • There is no 406 MHz training frequency

ELT Basics: The Output • 121. 775 MHz – Continuous Transmission – Swept Tone

The Old Little L-Per

Controls • Mode Switch – Turns the unit OFF – Selects DF mode – Selects REC mode • The Mode switch determines how the LPer operates

Controls • Channel Switch – Selects the channel you wish to receive – If a position is blank – assume that there is no crystal installed – Units will have different channel options depending on which model your L-Per is

Controls • Sensitivity – This control is used to reduce the sensitivity of the receiver. – Always start with this at MAX – Reduce as you get closer to your target (more details later)

Controls • Volume – Set to a comfortable level – Keep as low as possible (and still hear the ELT) because… – Higher volumes reduce battery life – Volume has no effect on the indication on the meter

Controls • Dial Light switch – Lights the meter – Keep off unless operating at night – Easy to bump the switch and notice it in the daylight – Reduces battery life

General Operation Notes • ALWAYS TURN A FULL CIRCLE BEFORE TAKING A COMPASS HEADING • Use both REC and DF modes to verify the headings • Hold the L-Per with two hands at a full arm’s length, keep the mast perpendicular to the ground • Avoid power lines, large metal objects such as vehicles, buildings and signs when taking readings • Keep other team members at least 10 feet away when trying to determine headings • ALWAYS TURN A FULL CIRCLE BEFORE TAKING A COMPASS HEADING

If you can’t hear it… • If you can’t hear the ELT swept tone – You are too far away from the ELT – The ELT is broken • May be transmitting no audio or a continuous tone – There is no ELT transmitting • Unless you know for sure that the ELT is malfunctioning – don’t believe your L-Per readings

Two Modes of Operation • The Little L-Per has two modes of operation • Each mode has its strengths and weaknesses • Always use both to determine a heading • Both modes should point you in the same direction, if not something’s up!

REC vs DF • REC = RECEIVE MODE – More sensitive – Allows you to take headings further away from the ELT – No front/back ambiguity – Less Accurate • DF = DIRECTION FIND MODE – Not as sensitive as REC – Very accurate readings even at close range – Front/back ambiguity exists – More accurate headings than REC

DF Mode • The meter tells you what DIRECTION THE ELT IS COMING FROM • Objective is to center the needle on the meter • Centered needle indicates the ELT is directly in front of or behind you

DF Mode • Always turn in the direction the needle points • If the needle points right, turn right • If the needle points left, turn left

DF Mode • When the needle centers, the ELT is directly in front of you or directly behind you • There is a way to determine if it’s in front of or behind you…

DF Mode • To determine if the ELT is in front of or behind you… – Remember, the needle always points in the direction of the ELT – Turn slightly in one direction • If the needle moves in the OPPOSITE direction you are facing the ELT (re-center the needle before taking a compass heading) • If the needle moves in the SAME you were not facing the ELT, continue turning until the needle centers again, then re-check before taking the heading

REC Mode • The meter tells you HOW STRONG THE SIGNAL IS • Objective is obtain maximum signal reading – Max meter reading is to the right of the meter • In REC Mode Strongest reading occurs when ELT is off the LEFT side of the antenna (YOUR LEFT when holding the L-Per)

REC Mode Techniques • Start with Sensitivity at MAX • Reduce the Sensitivity so the needle is at mid-scale • Turn in a circle • Continue to turn in a circle – watch for meter readings that exceed mid-scale

REC Mode Techniques • When a reading exceeds mid-scale, reduce the sensitivity to re-center the needle • Keeping the highest reading at mid-scale makes it easy to determine if anything exceeds your previous highest reading • Find the one spot that has the highest meter reading • If you’ve followed this procedure, the highest reading you’ll see is midscale, everything else will be less than that • At the highest meter reading, take a heading

What if… • You get more than 1 direction you feel the ELT is coming from? • You can hear the ELT but can’t get the LPer to “tell” you a good heading? • REC and DF mode don’t agree?

Then try… • Double check your instrument settings • Have someone else double check your instrument settings • Try a different location – You don’t have to move far (sometimes) – Radio waves at 121. 5 MHz have a wavelength of about 8 feet

IF you can’t hear the ELT… • If you can’t hear the ELT that means: – There is no ELT transmitting – You are too far from the ELT to hear it – The ELT is malfunctioning and not producing the swept tone – You or your L-Per are having difficulties… • As a general rule, if you can’t hear the ELT’s swept tone, you shouldn’t trust the L -Per’s meter readings

The Old Little L-Per • The Old Little L-Per may produce needle movements with no ELT signal present • It may track random noise sources or interference from other radio transmitters

Reflections & Propagation • Generally VHF radio waves travel in line of sight • The waves will reflect off of many objects • Its possible to get closer to the ELT and no longer be able to hear it

Reflections & Propagation • Ideally radio waves propagate equally in all directions from an ELT antenna • Terrain, buildings, damage to the antenna can all cause the propagation to favor one direction over another

How do you take a compass reading?

Compass Heading • Once you determine what direction the ELT signal originates from – Take a compass heading – Record the information – Radio the information back to IC – Plot the heading on a map – IC will plot the heading on a map

Compass Heading • A second person must be used to take the compass heading • The compass person should only approach the L-Per operator after the operator is sure of the ELT direction

Compass Heading • The compass person needs to know whether the L-Per is in REC or DF Mode • How you measure the heading does not change between modes • How you interpret the heading does change

Compass Heading in REC • Shoot your azimuth standing on the right of the L-Per operator • Sight your compass over both antennas • Your compass reading is the magnetic heading toward the ELT

Compass Heading in DF • Shoot the azimuth standing on the right of the L-Per Operator • Sight your compass over the two antennas • Add 90 Degrees to the compass reading for the magnetic heading toward the ELT

Old Little L-Per Tips ‘n Tricks • The unit runs on two 9 v batteries – only 1 is needed for operation

The Future of ELTs Changes are in progress!

Future of ELTs • COSPAS-SARSAT will no longer monitor 121. 5 or 243 MHz as of: – February 1, 2009 • All ELTs must switch to 406 MHz – 406 MHz will be the only frequency monitored by the satellites • 406 MHz ELTs will also transmit on 121. 5 and/or 243 MHz for local homing

The New Little L-Per

The New Little L-Per

The New Little L-Per

The New Little L-Per • Very similar in operation to the Old Little LPer – The Sensitivity Control has been eliminated • Frequency Programmable – No Crystals to buy! – 108 -174 MHz and 215 -270 MHz standard • It floats!

The New Little L-Per • The Old Little L-Per has not been available for some time • New purchases will likely be toward the New Little L-Per • Production started in early 2006 • Current price $750