2008-8-4 10:45:56 #

根据下面这段摘自Harris Z5CD手册的描述，上面第7步的TP18电压应该为2.1V,但实际校准的时候怎么也到不了2.1V啊。
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 Z5 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 150W, 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 150W and calibrating we are telling the
micro that 700 represents 150W. The micro now calculates the Reflect Factor by
dividing the 150W by the square of 700 or
Reflect Factor = RFL PWR CAL (kW) / (A/D_RFL_PWR*A/D_RFL_PWR)
Reflect Factor = 150W / (700*700) = 0.000306
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 200W). The
Foldback level is set at 1.35:1 (which is 111W). 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:
A/D_RFL_PWR = SQRT(RFL_PWR / Reflect Factor)
A/D_RFL_PWR = SQRT(200W / 0.000306) = 808 (Fault) or
A/D_RFL_PWR = SQRT(111W / 0.000306) = 602 (Foldback)
VSWR protection is based on this A/D reading, which is directly proportional to a
reflected power level, not on a calculated VSWR reading.

jason

2008-8-4 10:49:38 #

主要是99MHz的Z5CD软件版本比较老，就没有可以调整Reflect Factor的选项。

jason

2008-8-4 20:05:18 #

第7步应该是：
用万用表测量生命支持版上TP18的电压，同时顺时针方向旋转R128，直到TP18的电压为2.1V或者达到最大值。

Jason