Oscar Brand entering hiw 53rd year broadcasting the "Folksong Festival" on WNYC
 

He has been on since December 9, 1945 and he's still on Saturdays at
2230 GMT-5/-4. (wnyc.org, medium wave only)

This is the Guiness record for longest continuous broadcast by the
same host on the same program on the same station.

Undoubtedly, #2 would be Alistair Cooke's "Letter from America" which
was on the BBC Home Service (after 1967 BBC Radio 4) from 1946 until
shortly before his death in 2004.

(www.bbc.co.uk/bbc7 is currently running ol er um classic LfA's
weekdays at 1315 with audio on demand)