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Page Title: Block Diagram of Signal Attenuator AT702 Circuitry
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below) is required when the dipole antenna
through six-step signal attenuator AT702
before application to the input of the tuning
o r coupler devices are used. Series cali-
bration (b below) is required when the dis-
u n i t . The purpose of the signal attenuator
i s to insert either zero or a fixed amount
cone, loop, or vertical antenna is used. In
either series or shunt calibration, the
o f resistive attenuation in the rf and if.
s e t t i n g of the six-step signal attenuator
s i g n a l path. This circuit arrangement is
(c below) affects the signal path.
d e s c r i b e d in paragraph 12.
a. Shunt Calibration Condition (fig. 1 and
12. Block Diagram of Signal Attenuator
2 ) . The following two circuit conditions
exist with the calibration switch set at the
AT702 Circuitry
SHUNT CAL position.
(1) The calibrating signal voltage from
Figure 4 shows the threefold functioning
impulse generator G701 has a path
of the six-step SIGNAL ATTENUATOR DB
of continuity through coaxial relay
c o n t r o l . This block diagram is based on
K 7 0 2 to the input of 20-db fixed
p l a c i n g the front-panel calibration switch
a t t e n u a t o r AT701. The calibrating
in the SERIES CAL & OPERATE position
signal is decreased in amplitude by
(fig. 2).  The s h a f t of the front-panel
a ratio of 10 to 1 (20-db), and is
applied through coaxial relay K701
three separate switches, which operate
t o the input of six-step signal at-
c i r c u i t s as described below:
t e n u a t o r AT702.
a. Rf Attenuating Circuit. The incoming
(2) T h e incoming rf signal applied to
r f signal is coupled through front-panel
SIGNAL INPUT jack J705 (fig. 2)
SIGNAL INPUT jack J705 and coaxial relay
is effectively removed from the
K701. This relay is energized in the
input to the test set. Therefore, no
SERIES CAL & OPERATE position of the
i n c o m i n g signal from the antenna
calibration switch, and a path of continuity
or coupler can affect the meter in-
is created to the input of rf six-step signal
dication when the test set is being
attenuator AT702. The six positions of the
calibrated by the shunt method.
S I G N A L ATTENUATOR DB control have
b . Series Calibration and Operate Con-
t h e following effect on the incoming rf
d i t i o n (fig. 2 and 3). The following two
circuit conditions exist with the calibration
(1) I n the 0 SUBST. ONLY position,
switch set at the SERIES CAL& OPERATE
z e r o attenuation is inserted in the.
r f signal path. Since the test set
(1) A n incoming signal, applied from
input circuit is not terminated with
the antenna or coupler through
a 50-ohm impedance in this position
S I G N A L INPUT jack J705, has a
of the attenuator, quantative
p a t h of continuity through coaxial
m e a s u r e m e n t s are meaningful only
relay K701 to six-step signal atten-
if the substitution method of opera-
u a t o r AT702.
tion (para 6b) is used. The 0 SUBST.
(2) The calibrating signal voltage from
ONLY position of the attenuator is
i m p u l s e generator G701 is inter-
usually used for taking relative
rupted from the input to 20-db fixed
measurements  of  broadband
a t t e n u a t o r AT701 (fig. 1) by de-
( n o i s e ) signal amplitude with the
energizing c o a x i a 1 relay K702
m a g n e t i c field probe, the electric
T h e r e f o r e , 20-db fixed attenuator
field probe, or the conductive cou-
AT701 is effectively removed from
the calibrating signal path and the
(2) In the 0 CW ONLY position, 10-db
f u l l calibrating signal voltage is
of attenuation is inserted in the rf
a v a i l a b l e at front-panel IMPULSE
s i g n a l path. This position of the
OUTPUT jack J717 (fig. 3).
c. Signal Attenuating Circuit. Figure 3
c o n t r o l provides a 50-ohm termi-
s h o w s that the incoming rf signal passes
n a t i o n to match the characteristic

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