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9-17.
Peak Detector.
Each of the modulation and demodulation inputs can be selected to the peak
detecting circuitry for the determination of% AM or kHz deviation. The peak detector circuitry provides DC
outputs equal to the negative and positive peak values of the input signal relative to the average DC level of the
signal. These levels are then digitized by the DVM and input to the processor where the modulation level is
determined.
9-18.
DVM Control.
Any one of ten internal or one external measurement point may be switched to the DVM
for level digitization. Switching is controlled by the processor so that measurements are made to provide
current display data. In general several measurement points must be input to obtain all the displayed data.
Therefore the processor continuously cycles the switch through the required inputs stopping at each one long
enough to digitize and input its level.
9-19.
The Internal DVM Select switch is followed by a range attenuator. As the processor cycles through the
inputs it sets the range attenuator according to the last cycle reading made at that input. Thus each internal
input is auto ranged over two decades to give three digit accuracy up to a maximum input of 10 volts. The
internal DVM inputs and their function are listed in table 9-1.
+ Peak Voltage
- Peak Voltage
Carrier Level
RF INPUT PWR
EXT FWD PWR
EXT RFL PWR
BATT VOLT
TEMP SENS VOLT
SINAD OUT
SINAD IN
Table 9-1.
Internal DVM Inputs
Positive modulation measurements
Negative modulation measurements
RF output level
Power level applied to the RF input/output
port
Forward power level on external inline
wattmeter element.
Reflected power level on external inline
wattmeter element.
voltage level at DC input jack on the rear
panel
+5V level signal the processor that the RF
load temperature is too high.
DC level proportional to the signal power at
the output of the SINAD notch filter.
DC level proportional to the signal power
at the input of the SINAD notch filter.
9-20.
External DVM inputs to the front panel jack are ranged by the processor over a four decade range
before being routed to the DVM switch. At the Internal/External DVM Select switch the external DVM FROM
RNG SW signal or the internal signal from the x0.1 Attenuator is selected to the DVM to A/D signal line for
digitization.
9-3
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