Choosing the proper transmitter for a species' size and behavior is the first step in every successful study. We offer both Argos PTTs, which transmit data through the Argos satellite constellation, and GSM transmitters, which send data through the mobile phone network. Our Argos PTTs range in size from 2 grams to 105 grams; our GSM transmitters range from 25 grams to 70 grams. Please use this flowchart and consider the following factors to determine which type of transmitter will best suit your study.

• What is the weight of the study species?
• Though conventional thinking suggests choosing a transmitter that weighs <3% of a bird's weight, some birds have carried greater than this percentage. Larger transmitters are more durable, so we recommend choosing the largest model that your bird can carry and meets your study objectives. Each species is different; therefore, it is crucial that you use proper discretion to determine the appropriate size transmitter for your project.
• What type of data is required to address your study objectives?
• Our Solar PTTs, 45g and 95g Battery Powered PTTs, and Implantable PTTs provide Doppler-based location estimates derived through the Argos system. These locations have a minimum error of <250 m (Location Class 3). Argos-derived locations are often sufficient for studies of long-range migrant species and provide insight on their migration routes, stopover locations, mortality, and migration times.
• Solar Argos/GPS PTTs and the Battery Powered Argos/GPS 105g LC4™ PTT are equipped with highly accurate (horizontal accuracy ±18 m, vertical accuracy ±22 m) GPS receivers. In addition to migratory information, these transmitters are especially effective for understanding fine-scale habitat use and mortality.
• Solar-powered GPS/GSM 20-70 Transmitters send data through the GSM mobile phone network (our transmitters use 2G and 3G protocols). They collect high-resolution GPS data up to once a minute, depending on the current battery voltage and sun exposure, and transmit daily where possible. GSM transmitters archive data, so if a bird is out of cellular network range, the dataset is retained and will be transmitted during the next available cell connection.
• Will Ground Track (GT™) benefit your study?
• Our optional GT™ feature enables transmitters to emit a UHF signal allowing researchers to pinpoint a PTT's location. GT™ is helpful for locating PTTs in mortality and behavioral studies, and adds less than 0.5 grams to the weight of a transmitter (Solar 2g PTTs, Solar 5g PTTs, and GSM transmitters are not available with GT™).
  

	TRANSMITTER TYPE
Key Transmitter Features & Options	Solar PTTs	Solar Argos/GPS PTTs	Battery Powered PTTs	Implantable PTTs	GPS/GSM 20-70 Transmitters
Solar powered
GPS accuracy
Argos-calculated Doppler locations
Near-real-time global coverage*
High GPS fix rate & onboard data archive
GT™ option available
Extra pressure-resistance option

Feature available for all models

Feature available for some models

* Data reception latency will vary due to several factors.