Telemetry is like a high-tech bell, and one of the very few modern improvements on traditional falconry. It helps to allow the falconer find a bird, or even locate a bird who has been swept away by winds or chased off by other raptors. Telemetry is made of two pieces - the transmitter and the receiver. Some have a third component which is a headset to help them track a signal more precisely.
The transmitter is what goes on the bird so that you can locate the bird again. This consists of a small piece that transmits and contains batteries and then an antenna. Transmitters are typically mounted on the leg or tail, but are now being mounted on the back as well. As an apprentice, a transmitter is an excellent investment to help you fly your hawk with less fear of losing her. As soon as you receive your transmitter, make a note of its frequency and channel on a few models of receivers. Should you lose your bird, you can contact other local falconers with the information in case they pick up her signal, also helping you to regain your hawk. For this reason you'll want to have good batteries, and remove them from the telemetry placing each battery into a separate container to reduce the amount of drain on the batteries. Carrying extra batteries can also help when you drop one or find that one is drained. Any transmitter can fall off or get ripped off in any number of ways. If you have multiple transmitters, color coding each and writing down each one's frequency as well as marking it on the receiver can be a great help in reducing confusion.
The receiver is what allows you to pick up the transmitter's signal. A good receiver is an expensive piece of equipment. You may want to work out a scenario where you share a receiver with another falconer and split the cost. Hopefully it will not be used much. Some falconers have encountered problems where their handheld receivers are mistaken by observers for guns. Falconers with a receiver that could be mistaken for any sort of weapon have often taken the precaution of spray painting the receiver pink or another color not easily mistaken for a weapon.
It's a skill to use a telemetry signal well to locate a hawk. First, before releasing the bird to hunt, turn on the receiver and check the signal. There may be multiple signals, or a signal may be coming from another bird and your bird's telemetry is actually turned off. Checking for one signal and ensuring that it is from the bird you assume it is from is important. Many falconers have turned on a receiver and tracked a signal back to their truck to find another transmitter that was left on. The key to effective use of telemetry is practice. Have a friend hide a transmitter and practice trying to locate it. Practice yourself placing a transmitter in different places and different environments noticing how the environment and orientation of the transmitter change the signal you receive.
The transmitter is sending out radio waves and the receiver is receiving these waves. Since these waves are being sent out from a single point, the waves can be blocked or can bounce. A bird may be to the north of a chain link fence, and you may be north of a chain link fence, but your receiver is picking up a signal to the south because the radio waves are bouncing off the chain link fence and reflecting back scattered in many directions. This can happen with buildings, particularly metal buildings, cliffs such as basalt, and many other hard surfaces. Similarly the waves may be absorbed giving a bit of a shadow. A bird may be to the north of you, but on the opposite side of a large tree trunk. The waves may be passing on either side and giving what appears to be two signals that the receiver is picking up. It's important to try to differentiate between a direct signal and a rebound signal.
The transmitter placement and type of transmitter will also make a difference in the signal that is given off. A leg mounted transmitter that has a long antenna will be laying horizontally if the bird in on the ground on a catch. The ground may absorb or reflect the signal depending on the material. The horizontal antenna will also need to be considered when orienting the receiver for best reception.
When you pull out a receiver to find the transmitter, first find the signal on full gain and the volume at a reasonable level. Check and re-gauge this by slowly turning in a circle holding the receiver horizontally and level as you turn. You should hear differences in the signal volume with the loudest signal likely being the direct signal. Some receivers also have a visual meter where you can watch a small indicator arm sweep which will help in determining the relative signal strengths. There may be a second loudest signal at exactly 180° away from the loudest signal. This may be a rebound from the environment and should indicate that the loudest signal is the direction of the transmitter. Of course in certain environments this may not hold true. Try holding the receiver directly vertically and turning slowly in a circle. Angle the receiver in different orientations and tip it so it is not level to account for the possible different angles the transmitter antenna could be at. The best angle is likely a 90° angle between horizontal and vertical to maximize the transmitter's signals against any environmental interference. You are trying to check and re-check the signal ensuring you are getting the primary signal and not a back door signal. The signal will be the strongest when the receiver's antenna and the transmitter's antenna are aligned in the same plane. If you are standing in a valley or a depression in the ground, try to get to higher ground to improve the reception. Direct line of sight between the transmitter and the receiver will give the best and most accurate direction. Getting higher up will help reduce the obstacles to the signal being received. Many falconers have even paid private pilots to take them up so that they can search for the signal and hope to recover a bird. As you work towards the strongest direct signal, sorting out what is interference and what is rebound, you will begin to turn the gain down to the lowest level that gives an audible signal. This will help to get the most accurate location of the bird. Always keep the antenna sweeping to identify the signal location and to identify any movement of the signal.
Telemetry can be used to identify which direction a bird is in, if it is moving, how far away the bird is, and how high up the bird is. If a very strong signal is received no matter which way the antenna is held, then the transmitter is very close. You may be under it, on top of it, or next to it. It may be bushes, trees, or tall grass is hiding the bird. At really close ranges, and with receivers that have an antenna that can be detached, there are some techniques where the antenna is removed and the falconer uses his own body to shield the receiver unit from the signals.
Finally, don't forget to observe what is going on around you. If there are crows mobbing, chances are they know where your Red-Tail is. If there are some little birds who are angry and chattering, they may know where your Cooper's Hawk is. Listen for her bells.