Using an extension cable to move the antenna is a simple way to get a better signal.
Why is this so effective? It gets the antenna above the stuff blocking the signal. Let’s say your PC is sitting on your desk and your Wi-Fi router is a few rooms over.
The metal shielding in the computer itself can mess with the signal (which is why desktop PCs have external Wi-Fi antennas). The metal shielding in your computer monitor doesn’t help, either. Even your body absorbs some signal if you’re between the antenna and the router. Everything else between the antenna and the router also dampens the signal and, in our homes, the majority of all that “stuff” is about desk height.
So if your router is on a side table in the living room and your computer is on your desk across the house, there’s a whole lot of waist-height junk between the two antennas.