(3) Low-Frequency Transmitter (AM-1)
A low-frequency transmitter developed by the Electrical Engineering Department of New York University was adapted to replace or supplement the T-49 and T-69 transmitters. The carrier frequencies used have been in the region 1 mc to 3 mc. The schematic of this set is shown in Figure 28, as operated at 3135 kc. The output is approximately 2 watts, and a typical air-to-ground range is 300 miles, although reception of more than 450 miles has been attained by both ground and air-borne receivers.
[figure]
Figure 28. Schematic diagram, AM-1 transmitter.
Information is introduced in a manner similar to that employed in conventional radiosonde transmitters: resistances are switched into the blocking-oscillator grid circuit. In the case of pressure or ballast-count, fixed resistors causing distinct blocking frequencies are used; for temperature, the switch introduces the thermistor resistances.
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