Poor Reception/Transmission on Mobile Phone

Poor Reception/Transmission On Mobile Phone

Fault symptoms
Poor reception/transmission on mobile phone.

Probable cause of fault
Poor connection to the mobile phone aerial. Fault diagnosis applies to the quarter-wave roof-mounted aerial for the car that is prewired for the Saab mobile phone (option).

Diagnostic help
Standing wave measurement may be helpful if the fault diagnosis procedure described below does not result in pinpointing the fault.

Check wiring harness.
Jiggle the wiring harness at several points and in different directions to reveal intermittent breaks and short-circuits in the leads. Observe the multimeter, test lamp or diagnostic instrument during the test.





Diagnostic Procedure

1 Check the coaxial cable between the mobile phone and the quarter-wave roof-mounted aerial.
- Disconnect both ends of the coaxial cable.
- Measure the resistance between the braiding and ground.
The resistance should be infinite.
- Measure the resistance between the centre conductor and ground.
The resistance should be infinite.
- Connect a jumper lead between the centre conductor and the braiding at one end.
- Measure the resistance between the centre conductor and ground at the other end.
The resistance should be < 1 ohm.

Test results OK?
YES
Continue with point 2.
NO
Replace the coaxial cable.
Continue with point 3, Final Check.






2 Checking the aerial roof mounting
- Remove the aerial from the roof, clean the aerial's attachment to the roof and the coaxial cable's connection to the aerial.
- Check that the aerial base is securely bolted (grounded) to the roof.
- Connect the coaxial cable to the aerial. Measure the resistance between the braiding and a good grounding point.
The resistance should be < 2 ohms.

Test results OK?
YES
Replace the aerial if necessary.
Attach the aerial.
Continue with point 3, Final Check.
NO
Attach the cable firmly or replace the cable.
If possible carry out standing wave measurement
(SWR should be > 1.5:1).
Continue with point 3, Final Check.






3 Final check
- Carry out a function check.
- Evaluate the function check.
- Check that the symptom has not recurred.

Has the symptom recurred?
YES
The fault lies either in:
1 the coaxial cable
2 the aerial
3 the handsfree unit.
Check the above components once again.
NO
The steps taken to rectify the fault were correct.