Nokia 2255 Leitfaden

Nokia Customer Care

2255 (RM-97)

Mobile Terminal

Antenna Description and

Troubleshooting

2255 (RM-97)

Antenna Description and Troubleshooting

Contents Page

Introduction ..................................................................................................................................................... 3

Stub Antenna ................................................................................................................................................3

Failures and Corrective Measures.............................................................................................................. 4

Installing the stub antenna ......................................................................................................................4

Uninstalling the stub antenna .................................................................................................................5

Damaged RF Feed Pin.............................................................................................................................. 6

Obstructed RF feed pad or missing matching circuit..................................................................... 6

Nokia Customer Care Antenna Description and Troubleshooting

2255(RM-97)

Introduction

This troubleshooting guide addresses potential failures that affect antenna performance

of the 2255, and discusses methods for correction of these failures.

Stub Antenna

The 2255 uses a single band stub antenna for CDMA CELL band. The antenna radiator is a

flex meander that is wrapped around a plastic connector and overmolded.

Figure 1: Main parts of stub antenna

Anchor

Overmolded

plastic

Feed contact

2255 (RM-97)

Antenna Description and Troubleshooting

Failures and Corrective Measures

Installing the stub antenna

Figure 2 shows the assembly of the stub antenna into the D-cover.

Figure 2: Installing a stub antenna

If no stub antenna is installed, the antenna gain will be degraded by more than 25 dB.

The stub has a hook on the antenna anchor which locks the antenna into the D-cover

when installed. See Figure 3.

Figure 3: Locking mechanism on antenna anchor

During antenna installation, the antenna anchor passes through a plastic loop in the

C-cover (See Figure 4). The antenna is the last item to be installed during assembly of the

mobile terminal.

Hook

Nokia Customer Care Antenna Description and Troubleshooting

2255(RM-97)

Figure 4: Antenna locked into D-cover and plastic loop in C-cover

Uninstalling the stub antenna

During disassembly of the mobile terminal, the antenna needs to be uninstalled first. To

uninstall an antenna, a special extraction tool is needed. The antenna should never be

extracted by force as the antenna and/or the D/C-covers may brake or be damaged.

Use the static portion of the extraction tool to align the tool onto the D-cover. A moving

lever passes though the RF connector hole and releases the hook from D-cover.

Figure 5: Position of antenna extraction tool onto D-cover

Whip/Stub antenna

Alignment part

RF connector hole

Lever

D-cover

2255 (RM-97)

Antenna Description and Troubleshooting

Damaged RF Feed Pin

The stub antenna has a spring clip feed contact that should properly touch the PWB.

Positioning of this pin is shown in Figure 2.

• If the RF feed pin is broken or bent the pin will not touch the PWB and the stub

antenna must be replaced. If the spring for the RF feed pin damaged, replace the

stub antenna.

• If the RF feed pin of the stub antenna does not touch the PWB, the antenna gain

will degrade by more than 25 dB.

Obstructed RF feed pad or missing matching circuit

If the RF feed pin is obstructed, removed or covered, the RF pin will not touch the PWB

and then the antenna performance will degrade.

• If corrosion is present or the pad is missing, replace the PWB and the mobile

terminal.

• If either pad is obstructed or covered, clean and/or clear the pad.

The antenna matching circuit is positioned next to the RF feed pad. If the matching

circuit is improperly installed or any of the components are missing, the antenna gain

will be degraded by about 25dB.

Figure 6: PWB layout of RF feed pad and matching circuit

Antenna pad

Matching circuit

3.9pF

4.7nH 4.7nH

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