AirDrop between WiFi networks I have a Fritzbox acting as WiFi Access point and handing my home DSL connection, DHCP etc. I also have an Airport Extreme connected via network cable to the Fritzbox, only creating a Wireless network.

The wireless networks on both the FritzBox an Airport have the same SSID, password etc. I can only see one WiFi network SSID when I search for available WiFi networks.

This appears to work okay, however I haven't figure a way to Airdrop from my phone which is often connected to the Fritzbox WiFi network, and my Mac which connects to the Airport WiFi network (due to location in the house).

Is there a way to set this up so Airdrop (and probably bonjour?) can see devices on both WiFi networks?
Basically, you need to establish a permanent wired Ethernet connection from one of the LAN ports on the FritzBox to the WAN port on the AirPort Extreme.

Then, configure the AirPort Extreme to create a wireless network using the same wireless network name, same wireless security settings and same password as the Fritzbox router.

The last step to check would be to make sure that the AirPort Extreme is configured to operate in Bridge Mode, so it will function correctly on the network.

From https://discussions.apple.com/thread/5152388?tstart=0

If you've already done all this, make sure that your cables are good and everything.  If all else fails, try turning it off and on again