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WARNING: Disconnect primary power prior to servicing.
Overall System Theory
This is now the highest possible number for the DAC_APC_REF and will limit the
transmitter power to 2.4kW.To prove that:
FWD PWR = APC Factor * DAC_APC_REF
FWD PWR = 3.03 * 792 = 2.4kW
4.7.2.5 EXC Factor and IPA Factor
When the transmitter Forward Power is calibrated, the micro samples the exciter
and IPA outputs and sends the A/D readings to the screen as:
• EXC_Factor [HOME, MORE, CONFIGURATION C,A,D,A]
• IPA_Factor [HOME, MORE, CONFIGURATION C,A,C]
The calibration merely takes the A/D reading for each of these and makes it equal to
100% in the Diagnostics metering of exciter and IPA power output. Since Drive
Level changes with frequency, so will these cal factors. The factory cal numbers are
in the factory test data sheet.
4.7.2.6 Reflect Factor and A/D_RFL_PWR
Reflect Factor is a calibration factor that is calculated during reflected power
calibration. To check the Reflect Factor press [HOME, MORE, CONFIGURATION
C,A,B]. All Z2 transmitters are factory calibrated by reversing the reflected coupler
(it now measures forward power) and adjusting for a reflected sample voltage of
2.1V at 60W, as measured at TP18 on the Life Support Board. This sample voltage
is low pass filtered on the Master Controller and then A/D converted in the micro
for metering. This A/D value shows up as A/D_RFL_PWR [HOME, MORE,
CONFIGURATION C,B], which at 2.1V should be very close to 700 (the A/D
converter is 10 bit for 0 to 1024 range, but the input to the A/D is not actually 2.1V).
By setting the RFL PWR CAL screen to 60W and calibrating we are telling the
micro that 700 represents 60W. The micro now calculates the Reflect Factor by
dividing the 60W by the square of 700 or
Reflect Factor = RFL PWR CAL (kW) / A/D_RFL_PWR
2
Reflect Factor = 60W / 700
2
= 0.000123
The A/D_RFL_PWR reading must be squared to make the voltage from the coupler
linearly track the transmitter power output (Power is the square of the voltage).
The actual VSWR fault level in the transmitter is set at 1.5:1 (which is 80W). The
Foldback level is set at 1.35:1 (which is 44W). The Reflect Factor can now be used
to set the fault and foldback levels by calculating the A/D_RFL_PWR number that
would represent a specific power level using the formula:
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