Here is the service manual with instructions for WLAN removal/installation  https://www.dell.com/support/manuals/en-us/precision-3660-workstation/prec_3660t_sm/removing-the-wlan-card?guid=guid-4162f0eb-cd1a-4276-a231-000ab0698863&lang=en-us

Note that there are two wires, one black, one white.  The antenna leads are attached to metal surface on the case and the whole chassis acts as signals receivers.  If you get weak signals, check to ensure both of the antenna connectors firmly connected to the Wifi card.  Or, swap the antenna leads around between black and white for testing.

For stronger signals, users can use external antenna connecting to a PCIe adapter.

Thanks for the post!

https://www.dell.com/support/manuals/en-us/precision-3660-workstation/prec_3660t_sm/removing-the-wlan-card?guid=guid-4162f0eb-cd1a-4276-a231-000ab0698863&lang=en-usbattleship online

This post does not show where the antenna wires are connected to the case.  Can someone share how this is accomplished?

@user_d96166​ 

From Page 29 of the Precision 3660 Tower Service Manual.

Thank you, this helps.