Here i show a realization of a clamp-on RF ammeter which is very useful to detect a radiation from RF cables or power supply cables due to standing waves.
Step 1: Scheme
The scheme is taken from http://www.qsl.net. In my case it's composed of an ammeter of 100uA, a PVC case and a ferrite clamp from Wurth Elektronik, 23.7 x 34 x 19mm, ref: 7427113. In case you are using another ferrite the value of the first resistor may change. For this ferrite, the resistor value can be chosen from 5 to 25 ohms depending on the sensitivity you want to achieve.
Step 2: Enclosure Box
Cut out the area for the ammeter in the PVC box and connect the PCB you have made following the scheme in the previous step.
Step 3: Ferrite Clamp
Cut out the area shown on the photo in the case of the ferrite clamp and wound 10 turns of thin wire.
Step 4: Assembling
Solder the PCB wires to the secondary wounding like on photo and you're done. The ferrite clamp can be fixed to the PVC box with a hot glue.