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<br />. <br /> <br />TECHNICAL <br /> <br />The sensitivity of the two receivers was tested with the five unimplanted <br />tags. The test showed the SR-40 was approximately three times less sensitive <br />than the RF-40 (Table 2). This meant that weak signals could not be easily <br />. picked up with the receiver used in most of the searching, as indicated in our <br /> <br />. <br /> <br />flight of June 15. <br /> <br />. <br /> Table 2. Relative Strength of the RF-40 and SR-40 <br /> Receivers Using Five Tags in Two Feet of Water in <br /> the Green River of Ouray, Utah, July 8, 1978 <br />. SR-40 RF-40 <br /> Transmi tter range (ft) range (ft) <br /> 40.600 (40.669) 16 48 <br />. <br /> 40.631 80 256 <br /> 40.640 16 80 <br /> 40.682 16 240 <br />. 40.691 64 208 <br /> <br />. <br /> <br />After initial equipment testing with the RF-40 receiver indicated the range <br />of the transmitters was sufficient for the study, a number of contradictory re- <br /> <br />. <br /> <br />sults were obtained that suggested the transmitters were not working properly. <br />Tests with the five tags that were not implanted in fish showed several things. <br />First, the tags varied greatly in their signal strength (Figure 3). Some <br />were weak, others strong. Secondly, water depth had a marked effect on signal <br />strength (Figure 3). Increased depth of water decreased the strength of the <br /> <br />. <br /> <br />18 <br /> <br />., <br />