Observations on Falconry Transmitter Tailmounting

By Louie Luksander

Ever since telemetry was introduced to falconry by Bob Berry and Bill Cochran in 1969 falconers have pondered how best to attach transmitters to their falcons. The first transmitters were patterned after falcon bells. Berry devised a replaceable battery scheme using a brass cage with a bewit slot on top. Combined with a tiny Cochran bird transmitter a falconer could then insert a bewit and affix the transmitter to the tarsi of a hawk. The bewit slot would also accept elastic bands for neck mounting. These basic design elements are still found in many transmitters today.

As a transmitter manufacturer since the mid 1970's I have had innumerable correspondence with falconers conveying transmitter attachments depicting a myriad of devices and techniques. A compilation could comprise an entertaining volume of itself. Of these the most widely experimental was the tailmount.

Our first tailmount production transmitters employed a method first introduced by Steve Baptiste of Reno, Nevada. A solderless electrical connector lug with loop was crimped and glued to the base of a deck feather shaft. A micro toothless alligator clip is soldered to the brass battery clip/bewit slot assembly of an LF series transmitter. The alligator clip fine jaws were bent and looped slightly on the opposing ends to form a locking ring when closed. This ring could be opened and closed to fit through the loop of the solderless lug on to the deck feather allowing easy placement of transmitter on and off the hawk.

As the use of falconry telemetry spread globally American and European falconers began introducing equipment to the Middle East. Two such falconers were Egon Mueller of then West Germany and Jacque Renaud of France. Gulf falconers initially resisted putting transmitters on their falcons and as soon became apparent would only consider transmitters on the tail. Mueller presented an LF series transmitter with a single hook wire clip that inserted into a stacked tube assembly. The bottom tube was glued on shaft of deck feather while top tube accepted the single hook spring. The single hook would squeeze when inserted in the tube and expand once through securing the transmitter on the tail. The transmitter was easily placed on the falcon but difficult to remove. Meanwhile Renaud came to visit and brought with him the rear end of a Saker falcon complete with tail feathers intact. We set about designing a tailmount that didn’t require casting in order to set an anchoring connector on the hawk. The result was a dual alligator clip design with rounded smooth jaws that grasped the shafts of both decks. The transmitter was a trick to put on the falcon and could be knocked off in a tussle with Houbara. Meuller’s single hook design was then modified to a dual hook version. The opposing hooks were formed of spring wire on the ends of a bent “V”. The two hooks could squeeze together and insert through tube to then release and lock securing the transmitter to the hawk’s tail. Subsequent Renaud production units were equipped with the dual wire clip tailmounts. Often referred to as the “French mount”, the design continues to be a mainstay in modern tailmount transmitters.

The biggest fear for most a falconers with tailmounting is losing a deck feather and dealing with the ramifications of follicle damage and the possibility the feather may not appear during the moult. There are characteristic aspects of a tailmounted transmitters that increase the chances of pulling a deck feather with inherent causes and effects that merit review.

Antenna wrapping:

Antenna wrapping occurs when a dangling or exposed transmitter antenna wire hits some lateral object. Falcons and hawks tend to skim over and under fence, telephone and power lines as well as exposed limbs shrubs and trees in flight. When an antenna wire hits one of these obstacles at some point between the base of the transmitter and the end of the antenna wire, the momentum of the antenna wire will cause the end of the antenna wire to bend and wrap around and momentarily hitch itself to the obstacle. This in turn will create an immediate jolt as the flying hawks’ deck feather is jerked at 180 degrees opposite its momentum. The deck feather may be pulled and if it doesn’t initially, may well eventually as the scenario is repeated. Antenna wrapping was particularly bothersome with the early 150 MHz frequency equipment with 18”, ¼ wave whip transmitter antennas. While striving to reduce antenna length we introduced the 216 MHz frequency band with a shorter 13”, ¼ wave antenna and offered transmitters with shorter clipped and tuned antennas for tail mounts. Today with base loaded antennas to enhance short antenna efficiency and the availability of even higher frequencies the problem of antenna wrapping may be largely abated.

Impacting and snagging:

Most all tail mounted transmitters use the top mounted dual hook wire clip attachment scheme. This is less conducive to wrapping and keeps the transmitter behind and away from the hawk’s feet. With top tail mounted transmitters one might examine the height that the body of the transmitter sits above the tail feathers. A hawk in pursuit may fly through a fence or skim under a wire, maneuver vegetation and ultimately crash through flora of the preferred quarry. The transmitter will sustain impacts at the front or head of the transmitter with the obstacles impeding flight and pulling on the deck feather. The thicker and higher a transmitter sits above the tail feathers the greater the chances of impacting. Repeated impacting may cause the loss of a deck feather. Depending on the angle of incidence, an obstacle may hit and deflect over the transmitter and tail feathers as the hawk passes. Of greater concern is an obstacle deflecting below the transmitter. The gap between the transmitter and the wire clip is an area where twigs, grasses and wires can catch, wedge and snag thereby jolting the deck feather similar to antenna wrapping. Longwingers and shortwingers have experienced feather loss in this manner.

Aerodynamics:

As raptors have evolved to excel at flight so should we scrutinize transmitter aerodynamic characteristics. A transmitter’s flight is sustained by the flying hawk it is attached to. Therefore the passive components of flight defined as, weight, lift and drag are applicable. Falcons pulling out of a stoop and goshawks sharply maneuvering through vegetation after quarry experience significant G forces and air flow that attached transmitters and mounts must also tolerate and withstand. A transmitter wire clipped to the mount on a deck form the basic elements of a lever. The wire clip is a rigid bar placed some distance from the deck mount tube or fulcrum. This simple machine will transmit any forces exerted on the radio to the feather shaft. The G’s present when the weight of the transmitter abruptly shifts direction and the aerodynamic components of drag and lift as air flows over the transmitter are forces that will transfer torque to the deck. The hawk must compensate for these forces in flight. Ideally any adverse effects caused by the transmitter should be nominal.

The maladies discussed not only apply to tailmounts but all mounts to some degree. Antenna wrapping, impacting, weight/G’s, aerodynamics and leveraging at an attachment point all apply in some fashion to neck, leg and backpack mounts and present considerations when choosing which to use. Ultimately the decision lies with the hawk. Some hawks simply don’t like transmitters on them in certain places and have been known to bite and tear and try to remove them. Thankfully we do have options and can eventually incorporate a transmitter in some acceptable routine.

We can only imagine what electronics technology lies ahead. Falconry telemetry has proven indispensable and we certainly won’t go backwards. As man and falcon record yet another millennium, and as long as there are electronics tracking devices, falconers will continue to seek better transmitter designs and contemplate how best to attach them.