Glossary

Antenna
A transmitter has an antenna which is either a whip or a loop. A whip antenna should be as long as possible to give the maximum range, without interfering with the animal´s behaviour. In most applications, antennae are 150mm to 300mm long. Sometimes a loop antenna is more practical, but it reduces the range by 30-40% and is directional. The loop can be enclosed within the package e.g. for implantation, or it can form the collar for attaching to the animal.

Argos
A satellite-based location and data collection system. Argos was implemented in 1978.

Battery
The life of a transmitter package is dictated by its pulse rate and the size of the battery. The battery size in turn is usually the most important factor in determining the package weight. Some compromise between these parameters is often necessary when working out the optimum specifications for a package size. There are a limited number of batteries to choose from, but the maximum permissable package weight is a limiting factor. Battery shape may also limit the choice. Sirtrack staff are very experienced in helping researchers to choose the optimum battery for the job.

Beacon
Equipment (more properly known as a Platform) including a radio transmitter, antenna, power supply and, possibly, sensors.

CLS
Collecte Localisation Satellites, a private company set up in 1986 by CNES, IFREMER (the French ocean agency) and a pool of French banks. It operates the Argos system, and other satellite-based location and data collection systems.

Collar
The piece worn around the animal´s neck; used to carry the transmitter.

Data
Information in digital form, i.e. able to be processed by computers.

Data collection
Gathering data, usually at a large number of sites spaced well apart. Satellites are particularly effective in that they gather data quickly from large areas of the globe.

Doppler Shift
A physical phenominon occuring when an observer and a source of acoustic or electromagnetic vibration are moving relative to each other. It produces a variation in the frequency of the wave received by the observer. This frequency increases or decreases according to whether the observer and the source are moving closer together or further apart. In the Argos system, the Doppler shift is used to locate the platforms

Duty Cycle
This is controlled by the microcontroller of a two-stage transmitter to turn the transmitter on and off at exact programmed intervals to save battery power and extend the operating life.

Front-to-back ratio
The term refers to tracking antennas and the pattern generated by the gain of the antenna. Correctly manufactured Yagi antennas have a good front-to-back ratio meaning the strongest signal will be detected when the antenna is directed at the transmitter and only a weak signal is detected in the opposite direction. Loop antennas on the other hand have an equal front-to-back ratio, meaning the signal strength is as strong in both directions and can cause confusion.

High Power Transmitter
A high power option is available. The high power unit runs on 10.8 volts and has about twice the range as a standard transmitter.

Long life Transmitters
An optional extra is a long life transmitter. This will run for almost twice as long as a standard transmitter and still have 70% of the range.

Message
In the Argos system, a set of data sent by a platform.

Platform
Equipment including a radio transmitter, antenna, power supply and, possibly, sensors. Sometimes also called a beacon.

PPM
Pulses per minute.

Pulse rate options
Most researchers find 40 pulses per minute (ppm) a good compromise between locating animals quickly and getting the optimum life out of the transmitter battery. Sixty ppm is often preferred when tracking a large number of animals at frequent intervals, particularly when operating from fixed sites using a null-peak system. Transmitters for marine mammals are often run at 80ppm or even 100ppm becuase they may be on the surface for just a few seconds. The pulse width is usually set at 18 milliseconds. Using a longer pulse width can make tracking easier under difficult conditions but this shortens the battery life.

Radio Tracking
The basic idea of radio tracking is to attach a transmitter to an animal. The transmitter emits a signal that can be picked up by a receiver. When a directional antenna is plugged into the receiver and pointed directly at the transmitter, a strong signal is received.

Range
The range of a transmitter depends on many variables and is almost impossible to predict with any accuracy. The power of the transmitter and size of its antenna, local topography, vegetation, quality of the receiving equipment, height of the animal, and even the soil type will all influence transmitter range (as will other factors).

Reed Switch
During the packaging process of a transmitter, a reed switch is incorporated into the circuitry, so the transmitter can be turned off with a magnet when it is not in use.

Sensor
A measuring instrument which converts a physical quantity, e.g. a pressure or temperature, or wind speed and direction, into an electrical signal.

Single-Stage Transmitter
Single-Stage transmitters consist of just an oscillator, whereas two-stage transmitters consist of an oscillator and an amplifier stage. Single-stage transmitters have a shorter range and are used when the study species is too small to carry a two-stage transmitter (they are about half the size and have half the power output). They are occasionally used when very long life is required and the limited range is not important - however there are many permutations on the weight/pulse rate/life combination.

Transmitters
Transmitters are electronic devices producing electromagnetic waves at a rate that is set during manufacture. The pulse rate and pulse width affect battery life. Satellite transmitters produce waves that travel a long way into space.

Triangulation
Triangulation is the process of pinpointing a transmitter by tacking a bearing of the transmitter from two or more fixed points. When the bearings are drawn on a map, the point of intersection is the exact position of the transmitter.

Two-Stage Transmitter
A two-stage transmitter is the most commonly used transmitter in wildlife tracking (it consists of a oscillator and an amplifier stage). It needs more power than a single-stage transmitter and is more expensive, but it has twice the range (typically they have ground-to-ground ranges of two to five kilometres). The Sirtrack two-stage transmitter is manufactured in a variety of formats to give the optimum layout for each type of package.