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Radar System Engineering

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564 PRIME POWER SUPPLIES FOR RADAR [SEC. 14.5<br />

excited from the d-c power supply. The plate current varies in proportion<br />

to nearly the fourth power of the rms value of the alternator<br />

output voltage. This provides a very sensitive signal voltage with a very<br />

short time constant if the filament is of small diameter. Such a diode<br />

must be ruggedly constructed in order to maintain the mechanical spacing<br />

of the tube elements, and thus the tube characteristics, even under severe<br />

mechanical vibration.<br />

FIQ.14.7.—KS-15O55electronicvoltage regulatordesignedby Bell TelephoneLaboratories.<br />

A conventional amplifier is used which must have sufficient gain to<br />

provide the required over-all sensitivity. Stable operation of the<br />

combination of voltage-sensitive element, amplifier, output stage, and<br />

alternator demands that the usual conditions for stability of a servo<br />

system be fulfilled.<br />

Direct current excitation for the alternator field is provided by a<br />

controlled rectifier fed from the alternator output. The controlled rectifier<br />

may be a combination of transformer and rectifier controlled by a saturable<br />

reactor, or it may have grid-controlled thyratrons for rectification.

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