Hey Mike, I JUST got the answer to this question this week. I have the 300bhs. This is what I was told by Major Malfunction on this forum "As for the TV antenna, there is a booster! If you look on the electrical outlet below the main TV where it plugs int, there is also the cable TV plug. On this face plate is a little black(?) button. Push that on and you will see a red light turn on. That's the signal booster. If you are using antenna TV, you want that in to get good quality reception. If you are on landline cable TV, you want this OFF. "
Hope this helps!
2016 Apex 300BHS
TV: 2005 Silverado Z71, 4x4 lowered and re-geared