Thanks for using the forums. With the Slingbox M1, you would need a cable box to be able to connect the video source. Unfortunately that particular Slingbox doesn't have a coax connection. The PRO-HD is the only Slingbox that does have a coax connection you would be able to use. This particular model is an older model that isn't currently supported but you may still be able to find one on amazon, which is one of our authorized retailers.
Hope this helps,
The Sling Moderation Team