Field strength meter is a “must have” equipment if you’re dealing with radio transmitter electronics. Here is one example of this kind of circuit that works for 2.4 GHz band:

Simple Field Strength Meter Circuit with Optional Amplifier circuit schematic

An optional amplifier can be inserted after the rectification, so it can be used to boost small signal. This circuit works only for short distance transmitter since the signal must be strong enough to pass the voltage barrier of the diodes bias.  [Source: qsl.net]