Optimizing Aerial Telemetry Tracking

Aircraft and Pilots

Finding the right aircraft with a functional telemetry tracking system and a knowledgeable pilot is an essential starting point. While cost is important, in the long run researchers will find it more economical to contract with vendors maintaining aircraft specifically configured to meet the needs of the tracking protocol. Aerial wildlife tracking systems are often thrown together in a make-shift manner. These simple configurations are pressed into service and are too often geared toward aircraft flexibility for the vendor and won’t provide the same level of efficiency as a dedicated telemetry aircraft. A properly equipped aircraft and a competent pilot will save not only time and funding, but will enable the researcher to get the data they are looking for. Dedicated telemetry aircraft are permanently or semi-permanently configured with sophisticated combinations of antennas and audio distribution systems.

In aviation, there is no substitute for experience. Natural resource flying can be demanding so select a pilot with as much experience as you can find. A competent natural resource pilot should have a minimum of 1000 hours. Don’t be afraid to ask about his or her experience and safety record.

Finding Signal Location

There are many antenna configurations in use to achieve signal location. Many are relatively simple systems representing a compromise between aircraft flexibility and a functional telemetry system for the researcher. Most of these systems consist of a pair of side facing Yagi or “H” antennae selectable using a 2-way switch box. Others may have a single rotatable antenna mounted on the belly of the aircraft that the observer controls from the cabin of the aircraft. If only determining a species status is needed, a simple Omni directional antenna may be all that is required. Dedicated telemetry aircraft will provide a combination of antennae and audio distribution systems.

Signal location can be broken down into two distinct phases, initial reception and final signal location. For initial signal reception, Owyhee Air relies primarily on a forward facing 4 element Yagi antenna. While this forward facing Yagi configuration typically has exceptional reception, downward and sideways reception is occasionally limited in rugged terrain. To compensate for this, Owyhee Air employs an Omni directional antennae installed on the belly of its aircraft used in conjunction with the Yagi. A TAC-2 switch box allows for simultaneous or individual monitoring of the Yagi and Omni antennae enhancing initial signal reception.

The Yagi antenna is used to provide a bearing to the signal. This is achieved by changing the aircraft heading (direction the Yagi is pointing) until the bearing to the strongest signal location is identified. A signal strength indicator installed on some radio receivers can be helpful in determining the direction of the strongest signal.

Vendors solely using side facing “H” or Yagi antennae typically use the standard general search pattern for side facing antennae (see the Telonics Quarterly. Vol. 10/Number 1/Spring & Summer 1997). Owyhee Air aircraft are configured to achieve final signal location by utilizing a combination of the forward facing Yagi and side facing RA-2A “H” antennae mounted on the left and right aircraft wing struts. A 3-way TAC-7 switch box is used to allow the operator to switch between the Yagi and left and right “H” antennae. Proceeding directly to the signal while utilizing the forward facing Yagi, the operator may elect to switch back and forth between the Yagi and either both or individual “H” antennae.

Forward Facing Yagi Antenna

The benefits of a forward facing Yagi antenna are three-fold. First, the ability to fly directly towards the signal using the Yagi eliminates much of the search pattern required using only side facing antennae. Secondly, since the greatest reception capability of the Yagi antenna is in the same plane as the aircraft heading, earlier signal reception is achieved while flying toward suitable habitat or previously known species positions. Finally, the “signal null” found near the 0 degree and 180 degree positions of side facing antennae may give the operator a false “lost signal” indication. Conversely, while flying toward the signal using the forward facing Yagi, no signal reception from the side facing antennae assures the operator that the aircraft is headed directly at the signal. When using a forward facing Yagi antenna, exclusive use of side facing antennae typically does not occur until final species positioning or visual sightings are to be recorded.

Audio Distribution

Audio distribution systems range from rudimentary to sophisticated. If the researcher is required to plug the coax cable from an antenna directly into the receiver and turn the receiver volume up so it can be heard over the drone of the aircraft, then it’s time to look for a new vendor. Dedicated telemetry aircraft typically utilize permanently mounted antenna coax cable, switch box(s) capable of selecting a single or multiple antennae, and telemetry receiver audio heard over the aircraft intercom system.

Enough can’t be said about the “team concept” between pilot and researcher in maximizing efficiency. Good communication between the pilot and researcher is essential and is accomplished by means of the aircraft intercom system. Telemetry receivers should be plugged into permanently mounted audio receptacles and telemetry receiver audio should be heard over the aircraft intercom system by both pilot and researcher.

Researchers will appreciate the value of comfortably fitting noise reducing (ANR) headsets and some vendors will provide these. Along with ANR headsets, Owyhee Air also utilizes a Telonics (TNR) telemetry receiver noise reduction unit. The Telonics TNR reduces receiver background interference while enhancing telemetry signals.

Occasionally, a researcher may find it useful to monitor two receivers simultaneously. For instance, when monitoring separate frequency band widths or monitoring for “lost” collars while searching for primary collars. Dedicated telemetry aircraft may be configured so that two receivers can be plugged into separate hard mounted audio jacks with individually selectable controls on the aircraft audio panel. When using two receivers, one antenna (Owyhee Air uses the Omni antenna) is then dedicated to the secondary receiver. The receiver providing the signal source can be quickly determined by selecting the audio on or off using the aircraft audio panel.

Today, aerial telemetry tracking has become refined and can be used to establish highly accurate positions which may be correlated to highly accurate GIS data sets. In these times of limited funding, choosing the right aircraft, equipment, and pilot will help ensure your success.

- John Romero