The following is the sequence to connect the CM-7777HD, into your antenna system.
Your Antenna>short coax cable from the antenna to the CM-7777HD Antenna In port>Out To TV port from CM-7777HD connects to long coax cable going into the house/structure>that long coax cable enters the house/structure and connects to the power inserter TO AMP port>power inserter TO TV port is connected to a coax cable that goes to a TV or to a splitter.
The 3rd port on the power inserter (mini USB) on the CM-7777HD Power Inserter labeled Power In, is connected to a USB cable that is in turn connected to the USB Power Adaptor that plugs into the wall outlet. If you do not get any lights from the CM-7777HD, and think that your CM-7777HD power adaptor might be the source of the problem, you can temporarily connect the USB power cable to a 5vdc phone charger adaptor.
If you are connecting the CM-7777HD indoors and have a power outlet available, you do not need to use the power inserter. You can connect the provided USB power cable to the USB port on the side of the CM-7777HD.
Voltage readings are taken while the CM-7777HD is not connected to the long coax cable that goes down into the house. The coax cable from the antenna can be connected to the preamplifier Input. There will be no voltage at that Input port.
(CM-7777HD 5VDC USB Power Supply) You should measure about 5VDC at the end of any cable that connects to the power inserter TO AMP port. The CM-7777HD has a green power light for 17dB gain(low) and a red power light for 30dB gain(high). One of the lights should be on while using either of the power options(power inserter, or directly connected to the mini USB port).
NOTE: If your antenna has a built-in preamplifier that requires power over the coax cable, installing the CM-7777HD and its power inserter while connected between your amplified antenna and its power source/inserter--This configuration will block the voltage from getting to your antenna's built in preamplifier and you'd likely get little or no signal to your system.