Sergeant Preston and his dog King met more trappers and prospectors than newspapermen, but there were at least three exceptions, according to plot summaries from J.David Goldin’s http://Radiogoldindex.com.
I am searching for more in the 630 episodes the Old Time Radio Researchers group has uploaded to the Internet Archive,
Faith in a Mountie — an editor is kidnapped while planning an exposé. Unfortunately that Internet Archive collection of the radio series has another episode mistitled with the name of this one.
White Water — The San Francisco Chronicle sends reporters to the Yukon, but a murderer waits…
The Minister’s Missing Money — the son of a newspaper publisher accidentally switches suitcases with a minister.
Newspaper Heroes on the Air 