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Use of Electrocardiographic Radio Telemetry to Determine Heart Rate in Ruminants

South Dakota Agricultural Experiment Station, Brookings

ABSTRACT

The instruments used in this series of experiments were designed to record the heart rate via radio telemetry techniques. A block diagram of the telemetry system is shown in Figure 1. The transmitter was implanted in the animal, which was allowed the freedom of a 12-ft-square pen. The antenna was a multi-strand conductor looped about the pen in a horizontal plane. The loops were approximately 6 in. apart, with the lowest near the floor and the highest slightly above the subject. The signal was transmitted from the antenna into the laboratory via a shielded cable. An Army Signal Corps BC-453B receiver was used to convert the weak frequency modulated radio frequency signal to a strong frequency modulated audio signal. At this point the audio signal was monitored with a speaker before demodulation by a Heathkit Model FM-4 frequency meter. This demodulated signal was coupled to the DC input jack of the 350–1600 ECG preamplifier, a submodule of the Sanborn 964 recorder, for a permanent record.