Most field strength circuits in Google are simply the germanium rectifier diode of a very simple passive AM "crystal" radio.
I assembled one so that I could tune my FM transmitter for maximum output signal.

 

Most field strength circuits in Google are simply the germanium rectifier diode of a very simple passive AM "crystal" radio.
I assembled one so that I could tune my FM transmitter for maximum output signal.

Yes and for what the thread starter wants that should be fine. I made crystal radios as a kid using the ancient 1N34a diodes. Heck I grew up a few miles from WHLI (Long Island) and less any power a 1N34a, a set of headphones and a dipole antenna I could listen to WHLI radio.

Ron

 

Both my smaller Fluke DMM and my bigger Beckman DMMs will give a good indication of an energized wire if I hold the black lead and bring the insulated red lead near the live wire. That works for 120 volts, 60 Hz, I have not tried it with DC or 50 Hz.

 

The thread starter does not want to detect an extremely high power nearby radio station. Instead he wants to detect a 60Hz electrical wire behind a wall (said in post #7).

 

The thread starter does not want to detect an extremely high power nearby radio station. Instead he wants to detect a 60Hz electrical wire behind a wall (said in post #7).

I got that, maybe if you went back and read some of my post you would get that. If I can find a local radio station using a 1N34a I am pretty sure the thread starter can use some of what I listed to find a mains power wire a few inches in a wall constructed of drywall.

Ron

 

OK, Iwent back and re-read the thread. The TS wants to trace wires in walls. That is very much different from reading field strength, because CORRECT wiring in walls mostly consists of a pair of wires, line and neutral, which mostly cancel out the 60 Hz electrical field.
There are different ways to trace wires in walls that mostly involve adding a signal to the wire pair and then tracking that signal with a selective detector device. I have one that is marketed as "Fox and Hound, and it works well in most instances. Where it does not work out is in a large room with a lot of very noisy LED lights. It seems that some brands of LED lights radiate a large amount of RF signal that seriously interferes with my tracer.
But there are a whole lot of wire-in-wall tracers available. And I am sure that a system with a small transmitter and using a small portable radio could be simple and cheap to build.

 

Audio and video systems detect AC electrical noise everywhere in a house if their input cables are not shielded.
The line, neutral and ground wires in ordinary electrical cables inside the walls do not cancel the electrical field.

 

Audio and video systems detect AC electrical noise everywhere in a house if their input cables are not shielded.
The line, neutral and ground wires in ordinary electrical cables inside the walls do not cancel the electrical field.

What I see on my multimeter coming close to a standard 2x#14 +ground is quite a bit less than when I approach a single 120 volt line wire. Certainly there is still hum, but much less field intensity.

 

Thank you everyone for your feedback. I will go a different route for trying to learn electronics.

 

One way to develop some understanding, aside from textbooks, is to visit the applications sections of some of the integrated circuit manufacturers. What you get is correct information for free. Those fake shows on you tube are only there to make money, unlike the applications explanations. Some of those that discuss power supplies and op-amp applications can be quite educational indeed.