User Manual

Operation RF-Orchestra!™ Transmitter Installation and Operation
5-26 6880493G02-C July 2000
Power Metering
The station power level is measured using internal and external power detectors and support
from the Distributor DSP. The combination of the Distributor DSP and the detectors form the
internal and external wattmeters. The power output is determined by sampling of the internal
and external detectors by the Distributor DSP when instructed to do so by the Host processor
(MC68360). The Host requests samples during FM keyups only. In the case of InFLEXion voice
traffic, which keys in AM modulation for the majority of the frame, the detector sampling is
done during the 90ms ReFLEX and FLEX synch portion of each InFLEXion frame. When the
transmitter is keyed for extended periods of time, the detectors are sampled approximately
once every 2 seconds.
A debug trace was incorporated into the RF-O! software for monitoring the output of each of
the wattmeters. To turn on the wattmeter trace enter the following command:
RFO FIPS: a 192 SPCQ 64
To turn off the wattmeter debug trace, type the following command:
RFO FIPS: a 193 SPCQ 64
Current wattmeter readings can also be read using the RFO FIPS: a 79 x and a 80 commands.
Note: When using the a 79 and a 80 commands, the readings displayed are for the last time the
transmitter keyed. Even if the transmitter is dekeyed, the readings may show power output.
Wattmeter readings are used by the RF-O! transmitter software for various purposes such as
alarm reporting, power cutback, power shutdown, and power leveling.
Wattmeter Calibration
When a detector is first installed, the accuracy of the wattmeter is within +/- 20%. To acquire
more accurate readings, calibrate both the internal and external wattmeters. Once the
wattmeters are calibrated, the readings are within +/- 5% accurate.
The process of calibration is fairly simple. The power is increased to a known output level (200
Watts) at each wattmeter using a calibrated power meter. Using the RFO FIPS: a 71 x y, the
RF-O! transmitter software is told the actual power output. The software then creates a
calibration factor using both the actual power reading and the reading it is getting from the
detector. From that point on it multiplies its readings by the calibration factor to acquire the