Wavetek 3000 - Remote RF Level Programming

As shown in the block diagram,
front-
panel RF level controlinvolves the Meter
Board, Attenuator
Drivemodule M41A-1,
and
the ProgrammableAttenuator . With the
front-panel BCD switch(Attenuator dial)
in anyposition
except
REMOTE,
Meter Board
relay K1 will
be energized ; thus the
OUTPUTVERNIERwill
be connected to the
+10
dBm/OdBm level circuitry .
NOTE
For clarity, quad
2-input
"or"
gate, IC4,
is
shown in the
block
diagram as a SPDT relay . With
BCD switch in any position except
REMOTE, this circuit
is
de-energi zed, therefore, the 80-40-
20-10 BCD swi tch output i s appl i ed
directly to Attenuator Drive module
M41A-1 .
Assume the front-panel Attenuatordial is
set for an output of -70 dBm (80 dB total
attenuation) .
The BCD switch grounds the
"80" wire,
which applies ground to pin 13
of ROM IC3 in
the M41A-1 . The"10","20",
and "40"
inputs to theROMremain "high" .
This turns
on the appropriateFET switches
to activate the 10
dB, 20 dB, and 40 dB
pads in the
ProgrammableAttenuator .
A
"high" on
ROM pin
3
de-energizesMeter
Board relay K2,
thus selecting
0
dBm
program voltage
for the OutputAmplifier .
Therefore, 0 dBm output
from
the
Output
Amplifier attenuated 70 dB by
the Pro-
grammable Attenuator
results in an out-
put of -70 dBm, as selected
by the front-
panel Attenuator dial .
NOTE
OPTION
1A
+10dBm output
is equivalent to the
"0"
BCD
switch
position, 0 dBm
corresponds to the "10"
BCD posi-
tion, and -10 dBm is the "20"
BCD
position, etc . The BCD number
indicates
the total attenuation in
the unit, including the +10dB/0
dB position
of
relay K2 and the
Programmable
Attenuator active
pads .
Remote
RF
Level Programming
In addition to theMeter Board, Attenuator
Drive module,
and-
Pro-gram&able Atten-
uator, remote
level programming also
requires a LevelProgram
Board and rear-
panel plug as shown in the
blockdiagram .
With front-panel BCD switch (Attenuator
dial) set
to
the REMOTE position, IC4 is
energized and the AttenuatorDrivemodule
input is switched
from the front-panel
BCD
switch to the
80-40-20-10 BCD input
from the rear-panel Level Programplug .
In the Attenuator dial REMOTE position,
MeterBoard relay K1 is de-energized,
therebydisabling the OUTPUT VERNIER
and
replacing it with "combined modulation/
level program output" voltage from the
Level Program Board .
Basically, the
rear-panel 80-40-20-10
BCD input determines
whether Meter . Board
relay
K2 selects +10 dBm or
0
dBm pro-
gram voltage, and also which Programmable
Attenuatorpads (if any) are activated
.
The negative voltage
applied across the
OUTPUT VERNIER control is also applied
to a voltage divider network in the "1
dB Program Select"circuit .
The
8-4-2-1
BCD input from the
rear-panel plug
activates
FET
switches to select voltage
points on the divider network corre-
sponding to
the
1 dB
steps
.
These voltage
points are,

in turn,
connected across