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Firmware Version :

ISP :

TD-W8961N v2 Firmware Version: Build 150630 Rel.34713

The default country for wireless settings when I bought this router was USA. I didn't change it for a while. Today I changed it Israel the place where I live. The wireless signal dropped a little (about 20% to 30%). I changed country back to USA but signal still weak. Then I restored the previous settings from a backup rom which I created along time ago, and the signal became strong again.
I tested this many times and I got the same result. Transmit power is always set to high and channel bandwidth is always set to 20 MHz.
There is no channel interference in my home and no other setting was changed except country.
I tested this many times with same result
Can you explain this please?.
I measured signal strength with WiFi Analyzer on my android phone.