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Model 415E
Section IV
Paragraphs 4-1 to 4-4
SICTiON l¥
PRINCIPLES OF OPERATION
4-1. GENERAL.
4-2 The 415E is a high-gain tuned amplifier
which
takes an input from a bolometer, crystal, or any audio
source, amplifies it and applies it to a meter calibrated
for use with square-law detectors.
With bolometer
or biased crystal operation, the Model 415E supplies
the appropriate bias current.
Figure 4-1 is a block
diagram which illustrates instrument operation. Refer
also to the schematic diagrams, Figures 5-11 and 5-12
which fold out of the manual for easy reference.
4-3. INPUT CIRCUITS.
4-4.
The input voltage is first routed through INPUT
switch, A1S1. In the HIGH position it is applieddirec-
tly to the first section of the range attenuator, A2S1.
When the INPUT switch is set to any other position but
HIGH, the input signal passes through transformer T1
whose turns ratio provides a 50 to 1 impedance trans¬
formation, converting a 50 to 200 ohm source to 2500
to 10,000 ohms (which is the range of best noise figure
for the INPUT AMPLIFIER).
I INPUT 1
AISI
rh
R3
IOOK
Figure 4-1.
Block Diagram
02152-1
4-1
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