Northern Prairie Wildlife Research Center
Brian L. Joynt, Institute for Wetland and Waterfowl Research, Ducks Unlimited, Inc., P.O. Box 1160, Stonewall, MB R0C 2Z0 Canada
The Prairie Habitat Joint Venture Assessment project uses radio-telemetry to determine mallard nest site selection and duckling survival. One hundred and fifty mallards are marked on each 25-mi2 site. Due to the number of birds, size of the area, limited transmitter range, and required level of accuracy, vehicle-mounted receiving systems are required to monitor the ducks. Time to obtain a bearing, comfort, and safety concerns dictated that the system be operated from within the vehicle. Financial restrictions also dictated that many of the tracking vehicles be rentals. An antenna mount was developed that would be accurate, durable, and strong enough to carry the necessary antenna system while keeping vehicle restoration costs to a minimum.
The system is built on a set of roof racks and can be adapted for vehicles with or without rain gutters. The long mast (with cross boom and antenna affixed) is held inside a shorter pipe and can be removed without removing the mount from the truck. In situations where antenna height is a concern, the mount can be adapted to allow the antenna to telescope up and down approximately 76 cm. This modification, however, may introduce another source of bearing error.
All parts are generally available. Only three items need to be built or supplied by a welder or machinist. Pre- and final assembly time is estimated at 3-5 hr. The cost of mount parts for a vehicle with rain gutters is approximately $300-$350 CDN ($225-$300 US), and an additional $200-$250 CDN for gutterless vehicles. Vehicle restoration costs range from $250-$400 CDN. Installation of a sun roof is one restoration option.
We presently have 24 of these systems in use, some of them are in their sixth field season. Our present system consists of two four- or five-element yagi antennas centered approximately 1.8 m above the vehicle's roof. This mount also has been used with two 3.8-m eight-element antennas. This mount can easily be adapted to other types of vehicles (e.g., suburbans, vans) and other types of antennae.