Do USB WiFi adapters supplement or replace existing WiFi antenna?

When using a laptop the internal antenna can only receive the WiFi signal that exists in that air space where it is located so it seems to me that plugging in a USB WiFi adapter into the laptop cannot increase the WiFi performance and yet that is the reason they are sold. Is it the case that the USB adapter adds another antenna and the two work together to increase the strength and quality of signal received? Is that how it works?

Both the reception/transfer speed for the internal Wi-Fi card is somewhat limited. External Wi-Fi cards are better, but does depend on the choice you make:

https://www.howtogeek.com/243330/how...r-your-laptop/

Thanks for the replies. In my case both router and laptop are dual band and the laptop internal wireless card gets it's WiFi signal from an antenna wire that is routed around the display screen (as most are, I believe). Back to my original question: - If an external WiFi card is plugged into a USB port does this add an extra antenna to add to the signal strength that the internal antenna receives or does plugging in an external card disable the internal antenna/card?

wiganken said:

Back to my original question: - If an external WiFi card is plugged into a USB port does this add an extra antenna to add to the signal strength that the internal antenna receives or does plugging in an external card disable the internal antenna/card?

I believe they use only their own antenna - it isn't supplemented by whatever antenna you may have in your machine - if that is what you mean.

The USB WiFi adapter will use it's own antenna, the built-in WiFi in the laptop will use the laptop's antenna, and the two will never intermix.

OK. I'll leave it there. Thanks to all.