User Guide

PAMS
Technical Documentation
NHD–4
Disassembly & Troubleshooting
Page 29
Original 11/97
CDMA TX Gain Control – Manual Controls
As the name suggests, the CDMA TX Manual Gain Control mechanism of
the Service Software provides a means to manually manipulate the output
power of the CDMA transmitter. This test is convenient for testing the two
gain control functions of the CDMA transmitter, the CDAGCT IC and
Auxiliary AGC.
You can find this control within the CDMA Quick Checks selection of the
Tests menu of the Service Software. The output power is controlled by
adjusting the slide bar up and down, or manually entering numeric values
within the text edit box. Use a spectrum analyzer with a 2 MHz span to
view the transmitter output.
This test is adjusting the CloopRef register value, a value that determines
the difference between the received power into the mobile and the
transmit power out of the mobile. Artificially adjusting it, as this test does,
results in a change in the transmit power level. For this test maximum
CDMA output power, about 24 dBm, is achieved with a decimal value of
approximately 105. Minimum CDMA output power is achieved with a
decimal entry of about 25. At this level the CDMA signal will be as low as
the noise floor.
Detector DC Voltage Check – AMPS
Measuring the detector voltage, TXI, is great way to test transmitter output
power without actually reading the RF output power. Probing the detector
with a DMM at N202 pin 1 will provide a DC voltage that directly
corresponds to the amount of RF power sampled by the detector (V114).
This is a good means to assist in isolating transmitter faults. Whether or
not the detector voltages are valid will inform you if power losses are
occurring before or after the final PA stage (CLY–10, V113).
The following table shows typical detector output voltages for each AMPS
output power level.
AMPS
Power Level
AMPS Output Pow-
er
( dBm )
Detector Voltage
TXI
at N202 pin 1
(V)
0–2 27 0.87
3 23 1.35
4 18 1.80
5 14 1.99
6 10 2.13
7 8 2.17