In Search of the Bermuda Triangle

 At 11:24, radio call-in show, mysterious caller.

https://www.youtube.com/watch?v=RLl3Gdu_mJ0

Season 1 (1977)

04	04	"The Bermuda Triangle"	H.G. Stark	Alan Lansburg	April 27, 1977	715

Next show was on bigfoot.

https://en.wikipedia.org/wiki/In_Search_of..._(TV_series)