I’m entirely convinced that Broadcom is just a shit brand in general to get with. I have to use a PCI wireless adapter from them in order to get Airport working on my Hackintosh and it drops off no matter if I use the 5GHz or 2.4GHz signals.
On Linux, the drop offs are even worse.
If you use Linux, just get a wireless adapter with an Intel chip, even if you’re more loyal to AMD. Just save yourself the headache, please.