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FR ONT-
PANEL
RFL EVEL CO NTRO L
W
hen Option 1 Α is installe d, the RF
o
u tpu t level is adjust-
able over α
r
ange of 110 dB (+13
d
Bm to -97
d
8m) as
follows: The output can be reduce d 10
d
B by level
p
rogram
relay Κ 2 on
M
eter
B
oard 8005 ; t h e P rogram mable Atten.
uator provides a n ot h er 90 dB ο1 attenuatio n in 10
d
B steps;
and
t
h e OU T PU T VERN IER provides co nti nuous adju st-
ment of the o u tput level over α 10 dB range. These co mbine
to pr ovi de α total attenuatio n ο 1 110 d8 ..
As
s
h own in the
b
lock diagram, front-panel RF level
control
involves the
M
eter Boa rd,
Αττσηυατοι Driver
mo du le Μ 41 Α-1, and th e Progra mm able Attenu ator. With
t
he front-panel
B
CD switc h (Atte nu ator d ial) i n any
p
osition exce pt REMOT E,
M
ete r Boa rd relay Κ 1 will be
energize d; thu s the O UT PU T VERN I ER will
b
e connected
to
t
he +10 dBm/0 dBm level ci r cuitry .
ΝΟΤΕ
For clarity, qu a d 2-inpu t "or" gate, 1C4, is shown in the
b
lock diagr a m η α SP OT relay.
W
it h the BCD switch in any
p
osition exce p t REM OT E, this circuit is
d
e-energized;
th e refor e, t h e 80-40-20-10 BCD switch
o
utpu t is applied
directly to Atte nu ator Driver module Μ41 Α-1 .
Assum e the front-panel Atte nuato r dial is set fo r an
o
utput
of -70 dB tn (80 dB total attenuatio n ) . T he
B
CD switch
gro unds the "80" wire, which applies ground to
p
in 13 of
R
OM IC3 in
t
he Μ41 Α-1 . The "10", "20", and "40"
inputs to the
R
OM remain "high ". Th is turns on
t
he
appropriate FE T switches to activate the 10 c1B, 20 dB,
a
nd 40 dB p ads in
t
he Pr ogra mma ble Atte nu ator . Α "h ig h "
on ROM pin 3
d
e-on σrgizes
M
ete r B oard relay Κ 2,
t
hu s
selecting 0 dBm pr ogram voltage for the Output Amplifier.
T
h e refo re, 0
d
8m output from t h e Output Amplifier
attenusted 70 dB by the Pr ogra mma ble Attenuator resu lts
in an
o
u tput of -70 dB m, as selected by the front-panel
Attenuator dial .
ΝΟΤΕ
+10
d
am output is eq uivalent to
t
he "0" BCD switch
positio n, 0 dB m corresponds to the "10" BCD
p
ositio n,
and -10 dBm is t h e "20" BCD
p
osition, etc .
T
he BCD
number ind icates the total attenuation in the unit, in-
cluding the +10 dB /0 dB position ο( relay Κ2 an d
t
he
Pr og ram mable Attenuator active pad s.
REMOT E RF LEVEL PR OG R AMM I N G
In
a
ddition to the
M
eter
B
oa rd , Atte nu ato r Drive r mo dule,
an d Pr og ramm a ble Α tteηυατοι , remote level programmi ng
also req uires α
L
evel
P
rogra m Board
a
nd rear-panel
p
l ug
as shown in the block diagram .
With front-panel
B
CD switch (Atten u ato r d ial) set to
t
he
REMOT E positio n, IC4 is
e
n ergize d
a
nd
t
h e Attenuator
Driver module input is switc h ed from
t
he front- panel
BCD s witc h to the 80-40-20-10
B
CD input
f
rom the
r
ear .
panel LEVEL PR OG RAM plug. In
t
he Attenuator
d
ial
REMOTE
p
ositio n,
M
eter B oard relay Κ 1 is de-ene r gized,
t h ereby
d
isabli ng the OUTP UT VERN I ER and r eplaci ng it
with th e "combine d modu lation/level p rogram
o
utpu t"
voltage
f
rom
t
he
L
evel Pr ogra m Board.
B
asically, th e
r
ear- p anel 80-00-20-10 BCD input
d
eterm ines
whether
M
eter Boa rd
r
elay Κ 2 selects +10 dBm o r 0 dBm
pr ogram voltage, and also wh ic h Prog ramm able Attenuator
pads (if any)
a
re activate d .
The
negative
voltage
app lied
across
the
OUTPUT
VERN IER co n trol is also
a
pp lied to α
v
oltage
d
ivider
networ k in
t
h e "1 dB Prog ram Select" circuit . Th e Β-4-2-1
B
CD in pu t from the
r
ear-panel plug activates FE T switches
to select voltage
p
oints on
t
he
d
ivide r networ k corre-
spo n d ing to
t
h e 1
d
B steps. These voltage points
a
re, in
turn, co n nected across anot h e r
voltage
d
ivider
in
the
"0 .1
d
8
P
rogram Select" circuit, Then,
r
ear- ρα ne1 . θ-.4- .2-.1
B
CD input activates more FE T switches to select voltage
poi nts on
t
his
d
ivider wh ic h co rrespon d to 0.1 dB steps.
The output of the FE T switch es is con nected
t
hr ough
Meter Board relay Κ 1 to t h e +10 dBm/0
d
Bm level
circuitry .
M
AI NTEN ANCE
No cali bratio n or main te nance should be requir ed fo r
t
h is
option, ot h er tha n that described in previous sections of
t
his manual for cali bration of the
M
eter Board. However,
if α malfunction of some
k
ind
s
hould ma ke it necessary to
re pair the boards,
t
hey can be safely probed with α hig h
i m pe dan ce probe s u c h as α scope
o
r OVM . Α logical
troubles hooting procedure of isolating the fa ult sh o u ld
be followed. The in teg r ated circuits, wh ich are most vul-
nerable to acci dental s h orts, are all in sockets for easy
replacement.
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