I have discovered that a sure way to kill the Airdrop link between a Retina iMac and iPhone is to use a WiFi" "extender" nearby. I am using a Huawei LTE router for internet access and it links to my Mac and the "extender" (used to get signal to distant parts of the house) via WiFi. The moment I turn on the "extender" the previously working Airdrop fails - the other device disappears despite "everyone" being turned on etc. etc.
Turning off the extender again does not help. It has to be turned off and in addition the whole "remove Bluetooth plist" etc rigmarole gone through to reestablish the Airdrop link.
No one seems to have mentioned this issue before, so hopefully may be a new avenue for others more intelligent than me to look at - why does the extender kill the link, and what can be done to avoid it happening, other than never using an extender again (if you want functional Airdrop at the same time). Is the problem specific to certain WiFi/router combinations? I have tried rebooting both the main router and the extender, rebooting the iPhone and the iMac etc. but all that does not help unless the plist is removed. "Forgetting" the bluetooth identity on the Mac and the phone also does not fix it.
Incidentally, many people advise turning off the bluetooth on the Mac, but that is useless advice for the newer machines that come with bluetooth keyboards and mouse - the computer can't be controlled without the bluetooth link enabled. Having a USB keyboard etc. to hand would help, but I don't have any . . .
