I just got a TP-Link AC1570 router and noticed (via Wifi Analyzer, inSSIDer) a second "ghost signal" for each band (2 and 5 GHZ). The ghost signal shares the same channel and signal strength as the first and the same MAC address except the first two characters are different. It has no SSID name.
If I change the channel, the ghost signal changes also; if I turn the router off, the ghost signal disappears. (If I simply disable the wireless radio for the channel, the ghost signal remains.) I tried connecting to the ghost signal using the MAC address as the SSID name but that didn't work. I've gone through all the TP-Link settings but can't find any that appear to be relevant. The ghost signal is not a guest network: if I enable guest network, there is now a third signal for each band whose MAC is the same except for the first two characters--but the SSID for the guest network is not hidden.
What is the hidden signal? Does it interfere with performance?