Factors Influencing Radio Wave Transmission and Reception: Use of Radiotelemetry in Large River Systems

Abstract

Many technical and environmental variables affect radio wave transmission and reception in aquatic environments. We used a controlled experimental design in three large North American rivers (Illinois and Mississippi rivers, Illinois, and Skeena River, British Columbia) to examine the effects of water conductivity, transmitter depth, electromagnetic noise, antenna height, and transmitter type on detection distance. Detection distance was significantly affected by water conductivity, transmitter depth, and electromagnetic noise from a boat motor. Detection distance and maximum depth of signal reception increased with decreasing conductivity except at conductivities from 60 to 90 lS/cm (Skeena River). In contrast to terrestrial radiotelemetry, antenna height did not significantly affect detection distance. We also determined that a transmitter with a 3.5-V battery had an approximately 2.5 times greater detection distance than a transmitter with a 1.5-V battery. We provide quantitative results for several variables influencing radio wave transmission and reception, and we present two regression equations that can be used by researchers to obtain estimated detection distances in rivers of similar conductivity and depth. Furthermore, we compared our detection distances with those calculated from theoretical equations and found that our field results yielded higher detection distances. We strongly believe that there are gaps between results reported in technical papers and those obtained in field method studies; we argue for more collaborative research between aquatic telemetry users and engineers to reduce the current need for trial and error in telemetry study design.

Tracking animals in freshwater with electronic tags: past, present and future

“…Flatbed PIT antennas reasonably robust to ice processes [32] In small streams, use mobile PIT antennas through the ice [ Can use CART tags [22] A downrigger device has been developed that enables tracking of radio-tagged fish at depth, but has limited reception zone [37] Low-frequency radio tags can improve performance in deep water [35] as can use of more powerful batteries or stronger transmitter output [36] Abiotic Thermocline Thermoclines can impair the performance of acoustic transmitters [38,39], but radio transmitters are unaffected (aside from the fact that thermoclines often occur at depth)…”

Movement of Bigmouth Sleeper, Gobiomorus dormitor, in the Río Cañas, Puerto Rico, revealed by radio telemetry, and a discussion of the species’ amphidromous characterization

“…Radio transmitters have conductivity restrictions, but the signals should be clear in relatively shallow water (< 4 m) with conductivity < 800 μS/cm, but become less detectable after this conductivity threshold is reached (Peters et al 2008). Measurements taken in February 2007 about 1.25 km upstream of the Río Cañas mouth indicated that conductivities were acceptable for radio signal transmission (583 μS/cm; C. Mace, Mississippi State University, unpublished data).…”

Quantifying reception strength and omnidirectionality of underwater radio telemetry antennas: Advances and applications for fisheries research

“…The distance of the transmitted signal through water and water conductivity are paramount when determining expected range for radio telemetry (Eiler, 1990;Freund and Hartman, 2002) and detection distance exponentially decreases with increased distance that a signal must travel through water (Peters et al, 2008). Another consideration for employing underwater radio antennas, is the ease of creation.…”

“…Niemela et al, 1993;Martinelli and Shively, 1997;Brown et al, 2006); however, there are only a few applications of underwater radio antennas mentioned in the primary literature (e.g., Bunt et al, 2003;Beeman et al, 2004;Brown et al, 2006;Peters et al, 2008). This paucity of information on underwater radio antennas necessitates further research on antenna design and understanding (Beeman et al, 2004), since many useful applications exist in the study of aquatic organisms.…”