TM 32-6625-022-24&P
the output of the differential amplifier starts to change.
trace. When the sweep generator is in the MAN and/or CW
This change will be in a direction that will prevent further
mode, the vertical blanking is rendered inoperative.
change in the RF output amplitude.
3-12 MARKER CIRCUITRY. The marker circuitry pro-
vides accurate frequency identification of the detected
3-9 RF ATTENUATOR CIRCUITRY. The RF attenuator
RF signal. It consists of sweep sample divider/EXT marker,
switch is an eight position detent type using series double
harmonic markers, and marker stages. The sweep sample
pipads for the 10 dB through 70 dB positions. Accuracy at
divider stage selects a portion of the swept RF signal
higher frequencies is maintained by using precision resistors
which is coupled to, and mixed with, the harmonic markers.
and mounting the components in a coaxial configuration in
The resultant beat, or difference, is referred to as "birdy"
such a way that a 50 ohm characteristic impedance is
markers. The "birdy" markers produced by mixing are
maintained. The output of the RF attenuator is connected
amplified by the marker stage and are then superimposed
to the front panel RF OUT connector.
upon the detected RF signal from the device under test.
External marker signals are connected to the external
marker mixer stage through the front power EXT MKR
3-10 RF DETECTOR CIRCUITRY. The RF detector
IN connector as the other input. The resultant external
circuitry is provided to detect the RF output of the device
"birdy" marker is coupled through EXT MKR SIZE con-
under test. The RF detector utilizes a single video detec-
trol, amplified by the marker stage, and superimposed
tor diode, in conjunction with precision 100 ohm resistors
upon the detected RF signal from the device under test.
in parallel, to provide a 50 ohm load and adequate fre-
quency response over the operating range.
3-13 POWER SUPPLY. The power supply provides all
voltages required by the internal circuits of the sweep
3-11 VERTICAL BLANKING. The vertical blanking
generator and requires 115 Vat, single phase, 60 or 400
provides a zero volt reference trace when the detected
Hz for operation. The power supply also provides a line
RF signal is displayed on an oscilloscope. The square wave
frequency signal for synchronization of the sweep gener-
from the sweep rate stage is coupled to the gate of a Field
ator in the LINE mode. In model B (serial number 475
Effect Transistor (FET). The FET then conducts during the
and above) a 15 ohm 2 watt resistor is placed in line with
retrace period to provide a zero volt reference on the scope
the supplied 115 Vat.
3-3/(3-4 Blank)
