Measuring antenna Field Strength with the meter, requires no power source of it's own. And it literally is not discreet and does not care what frequency the transmission is that's being measured. Police cars have pegged mine from over a block away.MEASURING FIELD STRENGTH
Your meter can measure the low levels of radio frequency (RF) generated by a radio transmitter. You can use these measurements to map the transmitting direction and coverage pattern of your antenna, or to compare your radio and antenna's efficiency before and after an adjustment. You do not need to connect the meter to the antenna or the radio to measure field strength.
It takes two people to measure field strength. For an accurate measurement, you will need to map the site around your antenna. Then, while someone presses the radio's transmit key, you will need to walk around the site around your antenna with the meter, marking the readings you see.
Make sure there is at least 25 feet of open space in all directions around your antenna.