Rf Output Control; Digital Multimeter - Crown FM500 User Manual

3.7

RF Output Control

Set this control for the desired output power level. Preferably, set the power with an
external RF wattmeter connected in the coaxial line to the antenna. You may also use
the RF power reading on the digital multimeter.
The control sets the RF output voltage. Actual RF output power varies as the approxi-
mate square of the relative setting of the control. For example, a setting of "50" is
approximately 1/4 full power. Operation below 100 watts is not recommended as
instability can occur which could damage the transmitter.
Operation below 100 watts can cause
oscillations and other problems that
could damage the transmitter.
3.8

Digital Multimeter

The four-digit numeric display in the center of the front panel provides information
on transmitter operation. Use the "Up" and "down" push-buttons to select one of
the following parameters. A green LED indicates the one selected.
Digital Multimeter Multimeter Functions Multimeter Push-buttons
Audio Input
2
High Band
High
Expand Compress
2
Wide Band
-6
-12 +6 dB +12 dB
-18
Low
Input Gain Processing
Illustration 3–3 Digital Multimeter
RF Power—Actually reads RF voltage squared, so the accuracy can be affected by
VSWR (Voltage Standing-Wave Ratio). See section 5.4 for calibration. Requires
calibration with the RF reflectometer being used.
SWR—Direct reading of the antenna standing-wave ratio (the ratio of the desired
load impedance, 50 ohms, to actual load).
Operation
CAUTION
Possible equipment damage!
10
RF Power
SWR
20
ALC
PA DC Volts
PA DC Amps
PA Temperature
Supply DC Volts
Voltmeter
®
Fault Modulation Carrier
SWR Over
Lock
100
Input 90
PA DC 80
PA Temp
70
60
Power
50
Stereo
40
30
20
Pilot
Mono RF Output
FM500
FM BROADCAST TRANSMITTER
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