were taken. The model was operated at distances of from 10 feet to over 650 feet away from 
the console equipment. Control and readout communications were maintained throughout the 
range except in several instances when several observers intercepted the line-of-sight RF 
path. In these instances, the power to all model equipment was turned off by the fail-safe 
circuitry. There was no noticeable loss of signal due to multipath reflections. 
8. RECOMMENDATIONS 
The design of the system is based on the use of modular components for both the 
console and the model equipment. Many portions of the system use vacuum-tube circuitry 
because transistorized equipment of equivalent electrical characteristics was not available 
when the design was in progress and material was being ordered. It will be possible to replace 
these components with similar transistorized items of superior characteristics as new equip- 
ment becomes available. 
Transistorized subcarrier oscillators with better linearity than those used in the 
system are just becoming available. Transistorized subcarrier discriminators with specifica- 
tions similar to those used in the present system are also available. Substitution of these 
components in the model equipment would result in a small reduction of weight and power 
consumption. It is possible that in a few years even greater improvements will be made in 
this type of equipment. 
If smaller receivers and subcarrier discriminators become available it should be 
possible to use the present console equipment to operate a completely new set of model 
equipment which would be suitable for use in 10- to 15-foot models. Since the propulsion 
requirements would be considerably less for this application, a much lighter battery and 
simpler propulsion motor and rudder control circuitry could be used. 
Solid state inverters are now available which meet or exceed the electrical specifica- 
tions of the motor-alternator used in the system with the exception of range of input voltage. 
It is believed that this could be taken care of with slight modification. 
Solid state power converters are presently being manufactured at ratings up to 
5 kilowatts and it may be possible in the near future to replace the motor-generators and 
error regulators of the present system with units of greater efficiency and lower weight. 
Other advantages gained by the replacement of the rotary equipment would be the elimination 
of gyroscopic effects and noise. Some reduction in maintenance might be achieved. 
Some modifications and additions which could be made to the existing equipment would 
result in improved performance. It now seems highly desirable to add an adjustable current- 
limiting circuit to the error regulators for the motor-generators. This would eliminate the 
need for fuses in the output of the motor-generator and also prevent the application of large 
momentary overloads to the propulsion motors. 
It may also be highly desirable to provide some method for obtaining a good impedance 
match between the motor-generators and the model propellers. This could be accomplished 
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