This video describes a simple RF demodulator / detector probe that you can use with your DMM or oscilloscope to measure the relative amplitude of an RF signal in your circuit. It is very useful for tuning or adjusting IF stages during alignment, filter responses, peaking RF circuits, and examining amplitude modulation characteristics. The video describes the circuit and its operation, and demonstrates how to use it and the typical results you'll achieve. It uses a pair of 1N34A Germanium diodes, but could also be built with other low capacitance, low bias diodes. Notes from the video can be found here:
http://www.qsl.net/w/w2aew//youtube/RF_detector_demodulator_probe.pdf