Nokia 6255 Leitfaden

Nokia Customer Care

6255/6255i/6256/6256i (RM-19)

Mobile Terminal

Antenna Description and

Troubleshooting

6255/6255i/6256/6256i (RM-19)

Antenna Description and Troubleshooting Nokia Customer Care

Contents Page

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

Whip Antenna ..............................................................................................................................................3

Failures and Corrective Measures.............................................................................................................. 5

Damaged Whips ........................................................................................................................................ 5

Antenna Position into D-cover ............................................................................................................. 6

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

Obstructed RF Feed Pad or Missing Matching Circuit ................................................................... 6

Broken or Missing Bottom Antenna Clip or Matching Circuit..................................................... 7

Obstructed Whip Stopper....................................................................................................................... 8

GPS Antenna .............................................................................................................................................. 9

Bluetooth Antenna................................................................................................................................ 10

Nokia Customer Care Antenna Description and Troubleshooting

6255/6255i/6256/6256i (RM-19)

Introduction

This troubleshooting guide addresses potential failures that affect antenna performance

of the 6255/6255i/6256/6256i, and discusses methods for correction of these failures.

Whip Antenna

Check the following minimum visual quality standards of the whip assembly:

• No physical cracks or mechanical defects.

• No excess oil, dirt, or particles appear on the parts.

• Whip cap and sheath over the mold parting line (flash or offset) is less

than 0.1 mm.

• NiTi extrusion must completely cover the NiTi wire. No uncovered NiTi wire can

be seen from the tube side.

• Proper printing is present (found on the plastic connector).

• Whip cap must be perpendicular to the NiTi wire (maximum of 5°).

• Antenna straw must not appear twisted, cracked, bent, or discolored.

• No gate flash greater than 0.1 mm anywhere on the assembly.

• Feed contact must appear at a 45-degree angle and must be free from damage,

deformation, or unusual bending.

• Straw must be approximately 5.0mm from the end of the split bottom stop.

Figure 1: Whip antenna assembly

Cap.

Stubby tower

Connector

Feed contact

Straw.

Telescopic tube

Bottom stopper

6255/6255i/6256/6256i (RM-19)

Antenna Description and Troubleshooting Nokia Customer Care

In addition, the connector area includes the NMP code, date code, and supplier

information.

Figure 2: NMP code, date code, and supplier information area

The whip antenna is shipped fully retracted with the telescopic section fully collapsed.

The feed contact must appear at a 45-degree angle and must be free from damage,

deformation, or unusual bending. The straw must be approximately 5.0mm from the end

of the bottom stop.

Nokia Customer Care Antenna Description and Troubleshooting

6255/6255i/6256/6256i (RM-19)

Failures and Corrective Measures

Figure 3: Whip retracted and whip extended

Note in Figure 3 that when the whip is properly installed, the cap clicks into the antenna

tower when the whip is fully retracted. When fully extended, the length from the end of

antenna tower to the top of the cap must be around 109mm.

Damaged Whips

Figure 4 shows what the whip must look like when it is retracted and extended. If the

whip is damaged, replace it.

Figure 4: Whip stand-alone in retracted and extended positions

6255/6255i/6256/6256i (RM-19)

Antenna Description and Troubleshooting Nokia Customer Care

Antenna Position into D-cover

The internal antenna and whip are assembled into the D-cover as shown in Figure 5. If

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

Figure 5: D-cover assembly

• If the whip antenna is missing, install one.

• If any part of the whip/stub antenna looks obviously damaged, then replace the

whip/stub antenna.

Note: To take the whip/stub antenna out of the D-cover, slightly twist the antenna to release locking

mechanism and take it out.

Damaged RF Feed Pin

The whip antenna has a spring clip feed contact that must properly touch the PWB. If the

RF feed pin of the whip antenna does not touch the PWB, the antenna gain will degrade

by more than 25 dB.

Figure 6: Spring clip feed contact on the whip antenna

• If the RF feed pin is broken, or bent such that the pin does not touch the PWB,

replace the whip antenna.

• If the spring for the RF feed pin damaged, replace the whip antenna.

Obstructed RF Feed Pad or Missing Matching Circuit

If any portion of the RF feed or ground pin is obstructed, removed, or covered, the RF pin

will not touch the PWB and the antenna performance will degrade. If the RF feed pin of

the whip antenna does not touch the PWB, the antenna gain will degrade by more than

25 dB.

Whip antenna

Nokia Customer Care Antenna Description and Troubleshooting

6255/6255i/6256/6256i (RM-19)

Figure 7: PWB layout of the RF feed pad and the matching circuit

The matching circuit is right next to the RF feed pad. The matching circuit consists of a

shunt inductor of 27nH, a series cap of 1.2pF, and a series inductor of 5.6nH. If the

matching circuit is not installed properly or any of the components are missing, the

extended antenna gain will be degraded by about 25dB and the retracted antenna gain

will degrade by about 15dB.

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

terminal.

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

Broken or Missing Bottom Antenna Clip or Matching Circuit

If the bottom antenna clip does not contact the whip stopper when the whip is fully

retracted, the internal antenna gain will degrade by about 4-5dB at Cell band and

3-10dB at PCS band when the whip is retracted.

The bottom matching circuit is right next to the bottom antenna clip and consists of a

series cap of 3.3pF and series inductor of 1.5nH. If the bottom matching circuit is not

installed properly or any of the two components are missing, then the retracted antenna

gain will degrade by about 15dB.

Matching circuit

RF feed pad

6255/6255i/6256/6256i (RM-19)

Antenna Description and Troubleshooting Nokia Customer Care

Figure 8: Bottom antenna clip and matching circuit

• If the antenna clip is installed backwards, is damaged, or is missing, install a new

bottom antenna clip in the correct position.

Obstructed Whip Stopper

If the whip stopper does not properly contact the bottom antenna clip, then the internal

antenna gain will degrade by about 4-5dB at Cell band and 3-10dB at PCS band when

the whip is retracted.

Figure 9: Whip stopper when the whip is fully retracted

• If the whip stopper is corroded or blocked by the whip straw, replace the whip

assembly.

• If the whip stopper is obstructed or dirty, remove the obstruction and/or dirt.

Bottom clip

Bottom matching

circuit

Whip stopper contaccts

the bottom antenna clip

Nokia Customer Care Antenna Description and Troubleshooting

6255/6255i/6256/6256i (RM-19)

GPS Antenna

The GPS antenna is a ceramic chip soldered on the PWB. It has a matching circuit of

series 0R and a shunt inductor of 2.7nH.

Figure 10: Position of the GPS antenna on the PWB

• If the GPS antenna looks obviously damaged, replace it.

• If the GPS antenna is not present, install one.

• If matching circuit is not properly installed or any of two components is missing,

install the proper matching circuit..

Figure 11: GPS matching circuit components

GPS antenna Matching circuit

0 Ohm resistor GPS matching inductor

Notch filter components

6255/6255i/6256/6256i (RM-19)

Antenna Description and Troubleshooting Nokia Customer Care

Bluetooth Antenna

The bluetooth (BT) antenna is an inverted F antenna (IFA) printed on PWB.

Figure 12: BT antenna on the PWB

Perform a visual inspection of the BT antenna to ensure that the edge plating is not

corroded, faulty, or peeling.

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