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S
ERV
IC
E
S
HEE
T 2 (Cont'd)
Diodes
A
4CR1, CR2, VR 1 and VR2 and
t
heir associated co mpo-
nents are
p
art of α
s
h a ping
n
et work
w
hich co mpensates
f
or
t
he
non-linear butput o f t he
p
ower sensor's
p
ower sensing
d
evice.
A
t
RF inputs
n
ea r t he
m
aximum power input (100
m
W
f
or Mode l
8481Α),
t
h e
p
ow e r se nsing
d
evice
i
s slightly more efficie n t and
t
h e
hybrid amplifier's gain is
r
educe d
s
l ig htly to pr ovide an overa ll
response t h at
i
s linear.
The combin at ion ofA4C5,
R
8 and R9
i
s one of
t
hree
R
C networks
in
t
he ac a mplifiers whi ch determine the high frequency
c
uto ff
(240 Hz) of th e 220 ±20 Hz bandpass.
A
4C1, C6 and C30 are line
n
oise filters.
R
ange Switc
h
The RANG E
s
witch and associated co mponents on the Α4 and Α5
assembli es
f
orm two separate attenuator networks and α
l
ow pass
filter (t h e filter
i
s shown
a
nd discussed on Service S h eet 3).
W
it h hi gher power RF inputs,
r
elatively high
v
o l tages a re
co uple d to the attenuator inputs. The hi gher the
v
oltage th e
m
ore
it
i
s atte nu ated, thus allowing
f
or
g
reater sensitivity n ee d e d fo r
low p ower measurements whil e providi ng the
n
eede d resolution
f o r eac h range. The
v
arious
l
evels of atte nuatio n p e rmit ten usa-
ble
r
ange
p
ositions from 3 μ
W
to 100 mW (full sca l e). The
f
ollow-
ing table shows the individual and combin e d effect of
t
he attenu-
ators on the ac signal.
The
b
andpass of the ac amplifiers in the
P
o w e r Meter is approxi-
mately 220 ±20 Hz. The
l
ower
c
utofffrequency (200 Hz)
i
s fixe d by
t
he co mbination
o
f A4C7 with A5R1,
A
5R2 and A4R19 ; also
A
4R15 wit h A5R3,
A
5R4,
A
5R5 and A4R20.
R
A
N
G
E
Switc
h
P
ositio
n
3 μω
10 μ
W
30 μ
W
100 μ
W
300 μ
W
1
M
W
3
m
W
10 MW
30 m
W
100 MW
N
etwo
rk
#1
(A51`11, R2 and
ΜΑ191
+ 1
+
1
+1
+1
1000
1000
+
100 Ό
+ 1000
+ 1000
1000
Atte
nu
ation
N
etwor
k
#2
(00,1`14,115
a nd
A4
R
20)
+1
10
100
-
1000
+
10
100
1000
+
10
100
-
1000
Total
+1
+ 101/2
10
103/ 2
10
2
. χ . 10 5/ 2
10
3
10 7 / 2
104
109/ 2
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