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SYNTH AF
J4
J~11
AF INPUT - - - - - - - ----S-T-EP _ _ _ - - : T E : -
-ls
AF IN-..:.....--..,...--....;
swiTCH
-...__A_n_E_N
--'r-....;
wmEBAND AMPL
I
INPUT
DET
RF
LOAD
<"
<
45
I
I
10.7 MHZ IF
<'
' - .....
10
>
'---PO_o~_i_R_.- ~>----~~..:;_,._RF
INPUT PWR
WATT
14
.?'5
I
MTR EN
--'--«ool
DRIVER
-
?
c=~~~~=}------+~2~0_,..
I
I
TEMP SENS
I
•
OVER TEMP
-:!::-
.
I
I
7
INPUT
' - - - - - - - - - - - - - - - - - - - - - - - - ' - - PROTECTED
..
-------------------'
Figure 5-5.
Power Meter Block Diagram
5-38.
A sample of the RF voltage being applied to the RF Load is detected by the Power Detector to give a DC
output proportional to the peak RF voltage. The amplifier following the detector buffers and gain adjusts the
detected voltage to provide the RF INPUT POWER signal to the processor. The processor then determines and
displays the RF input power.
5-39.
A Temperature Sensor located near the flange of the RF Load alerts the processor when the load
temperature exceeds 80° C. The processor reacts to the OVER TEMPERATURE signal by displaying a warning
message on the CRT and by sounding the audible alarm.
5-40.
Monitor Mode
5-41.
The monitor mode allows RF signals from an antenna or from a transmitter directly to be checked for
frequency error. modulation level. and spectral content. AM. FM. and sideband modulations can be
accommodated with this system. A block diagram of the monitor mode is shown in figure 5-6.
5-42.
The RF signal to be monitored is applied to the RF Input jack on the RF Input module (A 11).1fthe input
level is less than 200 mW the input signal passes directly through the Input Protection circuitry to the Step
Attenuator. For input levels greater than 200 mW the protection circuit switches the input to the internal load
and signal the operator to switch to the Power Monitor mode. In this case. RF leakage (paragraph 5-37)
through the protection circuits provides the input signal to the Step Attenuator.
5-43.
For the monitor mode the T /R switch is set so that the RF input from the Step Attenuator is connected to
the RF port on the receive mixer. The output from the wideband amp is switched to the local oscillator port on
the receive mixer. The processor programs the RF Synthesizer for an output frequency that is offset from the
frequency to be monitored by 10.7 MHz. The offset may be above or below the center frequency as selected by
the front panel image switch.
5-14
L
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