User Guide

Nokia Customer Care

RM-1

RF Troubleshooting

Company Confidential

7A - 23

Issue 1

• If TX signal is not found at all use wider span setting and check if the transmitter is

transmitting on wrong frequency. If the signal is found to be on wrong frequency or

frequency is not stabile,

see section 3.1.3. "GSM transmitter frequency correct".

3.1.1 Does GSM TX transmit RF-power at all?

• If TX signal is not found at all use wider span setting and check if the transmitter is

transmitting on wrong frequency. If signal is found to be on wrong frequency or frequency

is not stabile,

see section 3.1.3. "GSM transmitter frequency correct".

3.1.1.1 Is Vinku (N7501) transmitting RF-power at all?

• GSM transmitter has to be active before Vinku’s output level can be measured. Procedure is

explained in chapter “General instructions for TX troubleshooting”.

• Measurements can be done with a spectrum analyser and an RF probe. RBW and VBW =

1 MHz, Span = 0, sweep time 1 ms. Spectrum analyser centre frequency should be set

according the used TX channel (see chapter “Frequency mappings”). Notice that GSM

transmission has pulsed nature and power should be measured during TX burst (triggering

needed). Another possibility is to use following settings: RBW = VBW = 1 MHz, Span 200 kHz

and sweep time at least 2.5 seconds.

• EGSM900:

- Connect the RF probe to Z7504 input. The level should be about the same on both input

pins. Check output level with at least the maximum (5) and the minimum (19) power

levels.

- Maximum power level – Output level should be about -15…-25 dBm

- Minimum power level – Output level should be about -45…-55 dBm

• DCS1800/PCS1900:

- Connect the RF probe to C7577 or C7575. The level should be about the same on both

capacitors. Check output level with at least the maximum (0) and the minimum (15) power

levels.

- Maximum power level – Output level should be about -25…-35 dBm

- Minimum power level – Output level should be about -55…-65 dBm

• Check if output levels of Vinku are as expected.

• NOTE! If VINKU output RF-power is totally missing just in one or two GSM-bands,

typically this means that Vinku ASIC (N7501) is faulty or the ASIC is badly soldered. For

example: VINKU is not transmitting at all in EGSM900-band but TX-power is ok in other

GSM-bands. Then it’s quite clear that VINKU (N7501) is faulty or badly soldered and the

component should be replaced.