@despairingcustomer

No, wrong frequency band I suspect. 225-ish MHz. You need helicals optimised for 2.4GHz, which is why I suggested WiFi antennas.

Tried it myself with a pair of old D-Link antennas and a bit of coax. Couldn't quite get WiFi in my garden shed, 50 feet from the cottage which has 30" thick solid stone walls. I can now get some signal, so in theory it may well work with extending Zigbee as it uses the same band.
Don't shoot me, I'm only the piano player. I DON'T work for or on behalf of EON.Next, but am willing to try and help if I can. Not on mains gas, mobile network or mains drainage. House heated almost entirely by baby dragons.