I recently purchased and AXE5400 router and two RE605X Range Extenders thinking they'd improve the wireless reception between my house and my shed.  I was previously using two Archer C7 (AC1750) and the reception was pretty poor. (I had to have the router no further than halfway into the shed.)

I purchased the RE605X as they advertise a 30dBm transmission instead of the 20dBm for the RE505X.

I put one Range Extender in the closest point in the house to the shed, and the other in the shed, in roughly the same place as the Archer C7.

Little did I know that even the 30dBm was sorely inadequate...  (I'm pretty disappointed in the Range Extenders, even in the house they are little better than just the router)

So my question is, is there a better option to give me suitable WiFi for security cameras in and around my shed?  Should I just return the two RE605X as they are inadequate?

Can I put an external antenna on the RE605X, my Archer C7s or is there a better solution?

Thank you in advance,

Rick