Repeated power cycling sometimes restored communication, but the evidence does not establish whether the cause is the internal power supply, radio conditions, serial interface, or modem firmware.
| Item | Observed result | Engineering significance |
|---|---|---|
| Terminal test | No AT-command responses during the fault | Confirms a local command-path symptom, not merely failed sensor polling |
| Power cycling | Repeated cycles eventually restored responses | Recovery is intermittent and does not identify the root cause |
Separate the Command Path from the Radio Link
However, the reported symptom is absence of AT-command replies in a terminal program.
Treat both radio-link loss and power-supply interference as hypotheses rather than confirmed causes.
Diagnostic and Verification Procedure
- Connect the terminal program using the same interface configuration used when the modem previously responded. Record whether the modem returns any response to the established AT-command sequence.
- Perform one controlled power cycle and repeat the identical terminal test. Record whether command responses return and whether recovery requires additional cycles.
Verify a correction by confirming repeatable AT-command responses after normal startups and successful polling of the five remote modems. If the fault persists, provide the manufacturer with paired working/failing terminal records and the controlled power-cycle results; repeated cycling alone is a recovery observation, not a corrective action.
FAQ
Radio connectivity, the serial command path, and the internal power supply require separate tests.
Compare local AT communication and remote polling before and after the antenna change.
Repeated power cycling restored responses in the reported cases, but recovery was inconsistent. Use a controlled cycle to document the symptom and escalate repeatable records rather than treating repeated cycling as a permanent fix.