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Faunatech Telemetry Antenna Towers

In many studies of animal behaviour and home range utilisation, simultaneous radiotracking from a number of fixed receiving stations can provide the most cost effective method of determining the movement of target animals. In a carefully designed study, large data sets can be gathered in a short period, and most importantly, the method of data collection is not likely to significantly affect those data, as would be the case, for example of a radio tracker crashing through undergrowth in pursuit of a telemetry fix.

Faunatech has developed a range of fixed and vehicle mounted telemetry towers in response to this need. A number of versions (eg. 6 metre or 9 metre), and options are offered. In this way a customised final product can be assembled to economically meet the requirements of a particular project. In all versions, judicious use of stainless steel, brass, plastic, fibreglass, galvanized or zinc passivated components and fittings ensure a long trouble free field service life.

Design criteria used in tower development were to:

• provide consistent and accurate bearing information;
• achieve high gain reception, allowing the use of low powered transmitters;
• be easy to operate accurately (even for inexperienced users);
• be ergonomic in its operation;
• be simple and straight forward to erect and transport;
• be built to last many years of field service;
• ensure safety to operators.

Fixed Tower Description

In broad terms, this system consists of

1. a hinged "crow's foot" base;
2. a lower structure supporting a thrust bearing, compass rose, lower mast and mid bearing;
3. middle mast and coupling, steel or fibreglass;
4. upper extension mast and coupling, steel or fibreglass (9 metre model only);
5. boom assembly;
6. antennae pair;
7. additional guy lines and slip-ring bearings (where appropriate);
8. cabling and null / peak switch box.

A galvanized steel "crow's foot" base accepts three long "crow's toes". Once secure, the base provides a safe and sturdy hinging axis for the entire remainder of the tower. As such, the assembly can be erected by one person, though for added safety we would recommend additional helpers for the larger models. For permanent deployments, the crow's foot base can be bolted directly to a concrete pad.

The design is such that it allows the operator to sit comfortably (without any mast structure between their legs) with compass rose and a full circle control wheel placed conveniently above their lap. The compass rose is specially cast to provide large easy to read numbers, a simple and reliable calibration adjustment, and most importantly it presents the 0 to 360 bearing sequence "in reverse". In this way, the indicated compass bearing will move under a stationary pointer (rather than the pointer moving around a stationary compass dial). As the pointer is always right in front of the operator, accurate and consistent readings over many hours are achieved with minimum operator discomfort (rotating pointers by comparison, invoke parallax error, as well as "a crick in the neck" as the operator must constantly monitor bearings on the opposite side of the compass rose).

A galvanized steel framework supports the mast riding on a sealed self-aligning thrust bearing, and a middle bearing (polyethylene on brass) at the three metre high position. Guy line attachment points are provided at this point. The upper mast is further stabilised by the inclusion of special nylon slip-ring bearings. This overall arrangement ensures a smoothly rotating, yet very stable telemetry system.

To reduce the risk of lightning strike and potential electrocution or of severe damage to the structure, the middle and upper sections of the tower are constructed from fibreglass tubing (although all-steel masts can be ordered if budgets are stressed). Note that the signal cables remain conductive, so while at a reduced risk, lightning strikes are still a possibility. To assist in ease of transport, all mast sections can be fitted with quick-to-assemble machined precision couplings. These are zinc passivated to guard against mating surfaces rusting together during long deployments. All components are precision jig drilled; this allows full interchangeability between individual towers.

The horizontal fibreglass boom is designed to accommodate a pair of up to 5 element Yagi antennae, although for some applications, a pair of lightweight "H" pattern antennae will suffice. Contact Faunatech for advice on antenna size and configuration. Finally, for studies requiring highly accurate fixes, the null-peak switch box is strongly recommended.

The towers can be ordered with a specially designed storm seal and canvas tent to protect operators in harsh conditions. Other options include a swing-out datasheet platen, boom lighting and a range of portable battery packs. Faunatech can also provide telemetry receivers and scanners.

Vehicle Mounted Towers

Two variations are available to the above systems to allow deployment from vehicles. The first requires a small hole through the roof of a van or 4WD vehicle. A customised folding mast hinge allows storage and transport of the upper mast on the roof, while a simple hinge and lock mechanism deploys the mast and enables operation of the apparatus from within the vehicle.

The second version does not require modification to the vehicle. Instead, a novel folding gantry complete with the mast assembly are attached to a standard roof rack. A simple folding action deploys the mast over the rear of the vehicle, ready to connect to a receiver. Erection time is a matter of minutes.