I have a Winegard AP8700 antenna pre-amp.

The thing is powered by a plug in the wall AC/DC converter rated at 18VDC. When I measure the output with no load it reads just over 15 VDC.

How accurate is the voltage regulation on those cheap power supplies. Will the pre-amp function even though it is running under a low voltage condition?

I have an AP4800 and it has an 8V voltage regulator in it. Winegard uses a standard circuit board for nearly all of its preamps and just changes the components on the board for different models. I'll bet the voltage regulator is the same in all of them. 15V is plenty. But I measured my 18V supply and it puts out 26V with no load so 15V does seem low.

Chuck

I would suspect that something is wrong with the power supply. A supply rated at 18 volts should put out at least 18 volts with no load. If the supply has no voltage regulator in it, it should put out a lot more than 18 volts with no load.