Wavetek 3000 Instruction Manual page 178

As shown in the block diagram,
front-
panel RF level control involves the Meter
Board, Attenuator Drive module M41A-1, and
the Programmable Attenuator . With the
front-panel BCD switch (Attenuator dial)
in any position except REMOTE, Meter Board
relay K1 will be
energized ; thus the
OUTPUT VERNIER will be connected to the
+10 dBm/O dBm 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 Attenuator dial 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 the ROM remain "high" .
This turns on the appropriate FET switches
to activate the 10 dB, 20 dB, and 40 dB
pads in the
Programmable Attenuator .
A "high" on ROM pin 3 de-energizes Meter
Board relay K2,
thus selecting 0 dBm
program voltage for the Output Amplifier .
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
+10 dBm 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 +10 dB/0
dB position of relay K2 and the
Programmable
Attenuator active
pads .
Remote RF Level Programming
In addition to the Meter Board, Attenuator
Drive module, and- Pro-gram&able Atten-
uator, remote
level programming also
requires a Level Program Board and rear-
panel plug as shown in the block diagram .
With front-panel BCD switch (Attenuator
dial) set to the REMOTE position, IC4 is
energized and the Attenuator Drive module
input is switched
from the front-panel
BCD switch to the 80-40-20-10 BCD input
from the rear-panel Level Program plug .
In the Attenuator dial REMOTE position,
Meter Board relay K1 is de-energized,
thereby disabling 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
Attenuator pads (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