[ADTech]

Unless you are measuring signal POWER (dBm, dBmv, dBuV), you often won't see any difference using the built-in signal meters.

The biggest difference between the PA18 and the CPA19 is that the CPA19 could be used anywhere a pre-amp was needed, including areas with a mix of weak and strong signals due to its excellent overload characteristics. The PA18 should be used in weak signal or fringe areas only. The CPA19 also has a filter that traps out the stuff from around 250 to 400 MHz (public safety, military, taxi, etc) that can cause interference into TV reception systems.