Just been reading about constructors trying to trace RF in their circuits.
Here's a neat trick to help fault find, the LED-O-METER.
All you need is 2 x 1N4148 or similar diodes (any old diodes will do really), and any old LED.
See the photo -
The LED-O-METER has a little flying tail to it (a bit of wire !) which you tap on to any point on the PCB to see if there's RF there (at least a few hundred milliwatts).
Or use it as a field strength meter with a longer wire attached, or with a simple connection to the output to tell you that your U3 / QCX ot any tx is transmitting.
Sensitivity can be controlled by using series capacitance or resistance in series with the flying tail part.
The LED-O-METER is a single ended device, no need for an earth.
