Wavetek 3001 Instruction Manual page 27

3,71
N
ARR OW OSCILLATOR
Th is oscillator also uses α va ractor diode so that the
frequency can be voltage controlled for phaso locking arid
for FM operation .
T
he coarse mo
d
ulati ng signal JFM) is applied to the
varactor from the Mo du lation Board (C316-2)
T h e fre-
ηυ eηεγ π1 th is 0sc ίllator IS further controlled by a "fine
t
un ing" bias voltage fr οιη t he Μ 33-2 phase
d
etector. The.
deviation can be co n t rolle d up to 100 kH z.
3.7 .4
LEVELERS
Th is modu le contains three RF leveli ng circ uits as shown
in
t
he
d
iagra
m
. These
m
aintain α constant amplitude RIF
ove r
t
h
e fre quency range and with temperature variation .
T
h e output of α
p
ea k d etector is compared in a constant
DC level . Any error is
a
mp lifie d and applied to a PIN
d
iode ατ te πιια tοτ in τenes wilh the RV signal .
3.8
M 10W-6/M10W-8-OU TPU T A MPLI F IER
M odel 3001 uses an Μ 1 Π W-Β Output Amplifier module,
while
M odel 3002 ιιτp . τ α"ι Μ Ι (1
V
V 8 .
T
he main fu nction it[ ιιι e Ρλ 10W-6 and N11OW-8 Output
Am plifier mo dules is to am plify the RF signal f
rom the .
M
9
W
to α level programmable
b
et
w
ee n -7 an d " 13 d Bm .
Λ leveler circuit maintains α constant amplitude output
signal over the wide Γregυeιιεγ
r
ange . The UNLEVELE D
light
d
rive r causes t he front panel ligh t to glow when the
levele r circu it exceeds its pr oper ope r ating range (see
Figure 3-13) .
T
h
e Μ 10W- θ (Model 3002) alsu con tains α switc h which
routes the RF output to either the Step Attenudlor or the
Μ l 15 for down -επηνers" ηη -
3.8 .1 SWITCH (Μ10W-8)
Th e switch is nor mally set to route the output signal to the
Step Attenuator ;
h
owever, when the front-panpi "MHz"
L
ever/Indicator switches are set to "000 ." . t h e logic signal
from
t
he Μ 115 into pin 5 of the Μ 10W-8 triggers t h e
switch ( relay Κ 1) and routes
t
he RF sig n al to the M115
3.8 .2 AMPLI F I ER
T
h is sectio n is α four-transistor . wide band amplifier whic h
can increase t h e RF by about 23 dB .
3.8 .3 LEVELER
T he leveler uses α peak detector, cl .iterennal amplifier, and
PIN dio de atte nuator. The peak d
etecto r 15 fed from the
3-12
RF ιπιιρυι . The resulting level is compared to α DC (or
AM) re! ιιιοηε e by the
d i fferential amp w h ic h su pplies the
ειιπΙιο 1 ειιrrεητ to the PIN diode altenuatoι. If the
d
etected
βF output
d
eviates fro m
t
h e reference level, t he signal to
t
he PIN
d io de causes t he input to he
d
ec rease d
o
r increase d.
In add itio n to
p
rovi ding α flat freque ncy response, t h e
leveler allows
f
or electronic co ntrol of the RF outp u t
amplitude by varying t he OC refe rence . The reference
co mes from
t
he
M
eter Boa rd (C315) .
3.8 .4
UNLE V ELED L IG H T D R I VER
W
hen the
d
iffere ntial am p in
t
h e leveler ci r cuit is putting
πυΙ α voltage. which woul d cause the PIN
d
iode αττεπυατοι
to be at its
h ig h or low resistance
E
mit, the leveling circ u it
can no longer be effective . These extreme voltage levels,
which are applied to the UNLEV E LED light
d
river, are
adequate
to
turn on
α sour ce
of c
u r rent for t h e i nd icator
whίrh app,' . αrτ thinug h
t
he Ι r.,ιηι Ιιαίιί "
3 .9 M172 -SWEEP DRIVE/DAC
This module provides two output voltages . One is linear
loom 0 V to -5 V as tile
f
requency gaps
f
rom 0 to 39 MHz,
repeating
e
v
ery 40 MHz;
t
he ot h er varies from +7 V -to -8 V
as the frequency goes from 0 to 520 MHz. The second
voltage is shaped to l ίn earize t h e VCO in the M
9W Sweet)
Oscillator
Two digital to analog converter ICs, programmed by the
front-ραπεΙ Lever/Indicator switc h es, pr ovide t
h
e 0 to 520
MHz vo l
tage . T h is iss h aped in th e n
ext section of t h e mod-
ule. Α third ΠΑ C
p
rovi d es the
r
epeating 0 40 ΜΗτ νοΙ t αge .
Since
t
he state of t h e 20's line depends on the 100*s low-,
t
he 20's line is inverte
d
w h en the 100's line is
h
igh .
Th e analog ιυηΙη9 signal from
t
he Μ 172 is "s haped" before.
d
rivi ng t h e. Mg W wide oscillator . Th e s h aper is an inverti ng
DC απιρ G( ί er w h ic h
a
mp lifies the input by α
s
maller factor
tat sm αηυι magnitu de inputs .
S
hap i ng t his analog voltage
eompensates tot tile non-linear change in capacitance of the
να r αιτο r (I rides in the. oscillator circuit .