RV Repair: RV antenna power supply trouble, antenna connection, noise filter

Question
I get nothing on my TV when plugged into the RV's Winegard amplified antenna connection.  I have already checked the cables individually from end to end and they are fine.  The amp box is putting out 12 vdc.  But with all of the coax cables removed from the antenna amp box, I read a short across the coax connection (0 ohms, center pin to outside jacket).  Is this correct?  What else can I check out?
Thanks,
Terry

Answer
Hi Terry:
Sounds like a bad amp box to me. When you ohm check the coax do you have it hooked to the TV? Take the amp box out of the system and hook the antenna directly to the TV you should get something. Most amp boxes amplify the noise as well as the signal, you could try a noise filter if the amp box does not have one in it. Good luck.
Bill