if the signal is deteriorating, there is a possibility of the antennas or the coaxial cables inside the phone failing. Coaxial cables are a quick replacement component, however, the board antennas are a soldering job. i would suggest having experience soldering before attempting it.
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besides this, the issue could also be the networking chipset. if this chipset is failing, the repair is likely not worth the trouble, as hiring a technician to do this repair would get extremely costly
if the signal is deteriorating, there is a possibility of the antennas or the coaxial cables inside the phone failing. Coaxial cables are a quick replacement component, however, the board antennas are a soldering job. i would suggest having experience soldering before attempting it.