Methodology for Efficiency Measurements of Electrically Small Monopoles for Animal Tracking

Abstract

For tracking purposes, small migratory birds are outfitted with antennas and transmitters so that their daily movements and migration patterns can be observed. In order to improve the practice of tracking wildlife and to extend the ranges over which animals can be tracked, it is necessary to characterize and fully exploit the parameters of the antennas being attached to animals. These birds provide a challenging opportunity to study the antennas used in wildlife tracking because of their small size (-15 cm in length) and light weight (averaging 26 g). For the first time, the present study provides a measurement methodology that can be used to estimate the efficiency of an electrically small antenna mounted to an approximate bird model, utilizing the Wheeler cap method. Because the antenna is less than one-eighth of a wavelength long and does not have a well-defined ground plane, measurement techniques are carefully considered and carried out. The results indicate that the bird model acts as a lossy ground plane for the transmitting monopole antenna. The radiating efficiency of the antennabird model system is conditioned by the size of the antenna as well as the effective resistance of the bird model. New recommendations for antenna and tracking-system design are provided, based on this investigation.

Radiotagged fledgling Savannah Sparrows Passerculus sandwichensis at risk of entanglement in vegetation

“…However, antenna length can have an impact on the detectable range, so this needs to be tested in the field to determine whether this solution is viable for use with grassland bird fledglings (Martin et al . ). To avoid the transmitter wedging under vegetation, potentially a wider or flatter transmitter that lies closer to the bird's body, such as models that are designed for reducing drag (Obrecht et al .…”

“…Most (five of seven) cases of entanglement in our study were due to the antenna entangling in the grass, and therefore trimming the antenna in half (6-7 cm) should reduce the risk of entanglement (Dougill et al 2000, Streby et al 2015. However, antenna length can have an impact on the detectable range, so this needs to be tested in the field to determine whether this solution is viable for use with grassland bird fledglings (Martin et al 2009). To avoid the transmitter wedging under vegetation, potentially a wider or flatter transmitter that lies closer to the bird's body, such as models that are designed for reducing drag (Obrecht et al 1988, Barron et al 2010, could potentially avoid this problem.…”

5.2 - LORA based Biotelemetry System for Large Land Mammals

“…When the animal is a bird the system must be slim and weightless [7]. Some scientists use tags with memory and (Global position system) GPS embedded, but it is necessary capture the bird to read the data, causing stress in the animals e arising the cost of the research [16]. The use of the GPS is very important for the animal tracking because its high precision data [14].…”

“…Systems using satellites are very efficient and the great advantage is the global service covering, even over oceans. The Argus service, initiated in 1978, with 12 active satellites over each hemisphere, works like an auxiliary system for animal and ships tracking, and maritime safety [8,15,16]. Sometimes there is no Argus satellite over the observed animal, causing a lack of contact which can remain for hours.…”

Flexible VHF Animal Collar Antenna for GPS-Aided Wildlife Tracking

“…The dimension of the cap is greater than or equal to l/2 to all directions from the antenna. The cap cancels out far-field radiation by reflecting all electric field radiations from the The antenna radiation efficiency measurements by using Wheeler cap method verifications are shown in [23][24][25]. The Wheeler cap applications to the HFSS simulation are shown in [24,25].…”