To find out when the Doc Martin television series airs on the PBS network, go to PBS.org. You will be asked to indicate and confirm your location.
After doing so, click on TV Schedules at the top of the page. A new window will open with a searchable TV schedule for your region. Click on Search TV Schedules and type "Doc Martin" in the search box that appears.
If the series is broadcast in your area, it will show up. Otherwise, you'll see a message that reads "0 results for doc martin." Alternately, you can download a PDF schedule and search the file for "Doc Martin" or any other show of your choice.