I've had a couple of those 841's and a 721 apart in the past and they are difficult to get back together wihout messing up the P/T mechanism because of the stacking of components & boards..... YMMV.
Because of that I would suggest a more powerful and sensitive wireless radio at the camera end, plugged into the cam's Ethernet port.
The idea is to use the camera's wired (Ethernet/RJ-45) port plugged into a
TP-LINK TL-WR802N Nano Router configured in "client" mode. You have power near the camera so this device would be placed near the camera, powered up with it's included 5VDC adapter and an Ethernet cable run to the camera. You could use a single, larger (amperage) 5VDC wall plug power supply to power BOTH the 841 and the TP-LINK if you didn't want to use two power supplies.
With your PC you log into the TP-LINK and set it up to use "client" mode, have it survey to locate the SSID (broadcast name) of your home's Wi-Fi, put in your home's Wi-Fi password and save it.
Once it reboots you move it over to the camera's RJ-45 port and it will access your home's Wi-Fi via the camera's Ethernet port. I have used this TP-LINK device to allow a dozen or more devices (laser printers, cameras, older xBoxes) that do not have wireless to connect to Wi-Fi with their Ethernet port.
Here's the instructions ==>>
How to Configure the Client Mode on TL-WR802N/TL-WR810N
Link to amazon in Germany ==>>
TP-LINK TL-WR802N Nano Router
There is also a dual band, 2.4GHz and 5GHz version ==>>
TP-Link TL-WR902AC AC750 WLAN Nano Router
I have not used them but
GL.iNet also makes several similar devices.