Wireless 'DNS' error; Latitute E6530 with Broadcom 802.11n keeps dropping connection

i have eliminated the problem being the modem or router.

so it is either the broadcom, or windows 10, or both.   any clues here?    

it is happening every 2 minutes, and can be fixed with the windows "troubleshooter" which gives a message that it is resetting the wi fi card.   and something about 'no DNS' problem.