The Roswell Report: Fact vs. Fiction in the New Mexico Desert

Output of the oscillator is both amplitude and frequency modulated, the amplitude modulation being limited by a class "C" RF amplifier. This unit weighed six ounces, was fed by a plate voltage of 270 volts with a filament drain of 400ma. at 1.5 volts. The output was one watt at frequencies from 25 to 100mc.

Before procurement of a receiver with automatic frequency control an attempt was made to develop a crystal controlled oscillator to overcome the frequency drift inherent in FM systems. This work was abandoned when the controlled receiver was obtained. The crystal control unit which was developed required extreme care in tuning in order that modulation be linear.

A miniature power amplifier, using one dual triode as a push-pull amplifier was constructed for use at 25 to 100mc with any of the above mentioned transmitters. The antennae for these transmitters was a half-wave vertical dipole.

The receiver found satisfactory for these systems was the R-2A/ARR-3 Sonobuoy receiver. This unit employs Automatic frequency control and will tolerate a drift $ - .35mc $ before retuning is required.

When SCR-658 radio direction finding equipment became available work on these transmitters was abandoned and a 400mc transmitter used. This system allows for accurate positioning of the balloon systems by use of crossed azemuths from several receiving stations.

A transmitter using pulse time modulation was designed for use with this receiving equipment. The advantages here are high peak power with relatively low input power (and thus a high signal to noise ratio) and simultaneous transmission of several data channels at one frequency. This project was abandoned before tests could be completed due to a modification of project requirements, but preliminary results indicated that this system would be advantageous in AM or FM transmission. This system makes use of short duration pulses ( .5 micro second) at a repetition rate of approximately 10 kc.

For long range transmission of information an amplitude-modulated transmitter was developed. (Fig. 6) This unit, the AM-1, is crystal controlled, employing a 3A4 miniature tube in a Pierce oscillator circuit as the crystal oscillator. This circuit does not require an LC tank circuit and eliminates the tuning of this additional stage. The RF amplifier is a 3A5 miniature dual triode tube. The unit was designed to give 1.5 watt output with a 270 volt plate supply and can be used with 380 volts to give 3 watt output.