ABSTRACT
During the period covered by this report, work was continued on developing an FM transmitter. Tests were made on FM Radio Receiver R-2a/ARR-5 and Radio Transmitter T-1B/CRT-1 to determine their performance characteristics, and compare the results with the transmitter system under development.
Necessary field equipment was constructed and an antenna was erected in preparation for field testing of the completed AM transmitter. A duplicate model of the AM transmitter was constructed and built into a container with a battery pack and simulated signal circuit.
a. PERSONNEL AND ADMINISTRATION
No change
b. COMMUNICATIONS
None
c. GENERAL WORK UNDERTAKEN DURING THIS PERIOD
It was called to our attention by the Watson Laboratories, Oakhurst Field Station, that the FM radio transmitter T1-b/CRT, which is a unit of Sonobuoy equipment AN/CRT-1, might have application in this project. Five of these transmitters were purchased from a surplus radio supply house. These units were tested for frequency stability under conditions of variation in plate and filament voltages. Deviation measurements were made at several values of plate voltage. These tests indicated that this transmitter would probably be unsatisfactory without a system of automatic frequency control. The receiver used with transmitter, B-2a/ARR-5, has an a.f.c. circuit incorporated. A receiver of this type was borrowed from the Oakhurst Field Station. Tests were conducted to determine the overall frequency drift which could be tolerated in the transmitter before returning became necessary. It was observed that as great as a $ \pm 0.55 $ mc shift could be tolerated at the transmitter. Further tests on the transmitter showed that the frequency deviation varied with input plate voltage and that as the battery depreciated, an error would be introduced in any amplitude measurement. For a plate voltage change from 155 to 90 volts, a variation in detected emplitude of over 20% was observed.