Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
35(78)
The modulated RX-signal is mixed down to 67.7 kHz in N300, and the IRA, IRB, QRA and
QRB are generated.
Those signals are measured in a fast ADC in N500 and the signal level is directly calculated
from the RX-I/Q signals.
The calibration measures the offset level i.e. the difference between the real and the measured
RSSI.
The difference is measured in dB and stored in the EEPROM to be used by the signal
program when calculating the RX signal level.
The RSSI is measured at Mid channel and the input signal has GMSK modulation.
For EGSM900 the frequency 942.4 MHz and the amplitude –68 dBm are used.
For GSM1800 the frequency 1842.6 MHz and amplitude –68 dBm are used.
10.2 RSSI measurement
Open the phone and check for liquid damage.
Go to Radio/RSSI Measurement and make a RSSI measurement.
EGSM900: Channel 37.
Set RX signal from the GSM test to 942.42 MHz and amplitude –50 dBm and GMSK mod-
ulation on.
Make sure the right RF amplitude is chosen.
The RSSI-value for an input signal of –50 dBm is about 0xC8. If you want to check on a
lower signal the RSSI-value for –100 dBm is about 0x48.
If RSSI is 0xFF (for different signal strength), the fault usually is due to N500.
If RSSI for an input signal of –50 dBm is low, is it advisable to follow the signal to find the
component that attenuates the signal too much, go to chapter 7 (“No serv/Network problem”).
GSM1800: Channel 669.
Set RX signal from the GSM test to 1842.62 MHz and amplitude –50 dBm and GMSK
modulation on.
Make sure the right RF amplitude is chosen.
The RSSI-value for an input signal of –50 dBm is about 0xC8. If you want to check on a
lower signal the RSSI-value for –100 dBm is about 0x48.
If RSSI is 0xFF (for different signal strength), the fault usually is due to N500.
If RSSI for an input signal of –50 dBm is low, is it advisable to follow the signal to find
the component that attenuates the signal too much, go to chapter 7 (“No serv/Networks
problems”).