Q&A for How to Build a Metal Detector

AM radio brand doesn't matter, but choose a small one to keep the weight down.

No, the radio on your cellphone can only receive FM whereas you need AM for this project.

The apparatus does not attract metal. It sends out electromagnetic waves that get bounced back to the antenna, changing the tone as it detects metal.

Possibly, but you may not be able to clear the static with a large radio. You would have to use trial and error to find out if it will work. You are looking for a specific tone.

You could use a brick wall high pass filter. You could have a low voltage relay switch that only closed when it had electricity running through it. Run the audio that you would have just listened to through the relay. You could control the sensitivity by changing the frequency cutoff of the limiter. And use that to run your switch. Probably would be better with two coils though.

Yes. Aluminium is diamagnetic, which means it would be affected by the metal detector. You can test it with a soda can.

You can use either one. All that is required is for the radio to be capable of tuning to AM radio. It is better to have an external antenna though.

Check out the pictures.

BestBuy or any other store that sells electronics would be a good place to start. You could also try Amazon or other online retailers.

The depth penetrated depends on the strength of the magnetic field and the composition of the medium you are trying to detect through. This is more complex math and takes more time and expertise than the average person has to put into detecting surface metal.

The calculator mostly creates a small magnetic field that interferes with the static and creates a humming sound by the antenna. You want the calculator's power circuit as close to the antenna as possible, so try moving it closer.

The calculator creates a small electrical field that interferes with the static, allowing the radio to pick up short range interference shot back to the antenna by the metal.

No, you must use the AM or FM/AM radio because FM's can't get the tone and AM's can.

Yes, but it would need to be a lot bigger, possibly an antenna. The person who you hypothetically are searching for would need to be carrying metal objects, and your detector would need to be long/deep range.

The depth penetrated depends on the strength of the magnetic field and the composition of the medium you are trying to detect through. This is more complex math and takes more time and expertise than the average person has to put into detecting surface metal.

It cannot because gold is a type of rock. There might be types that can detect gold but this type will only get you metal.