Metal Detectors

[NA4BH]

Any of you use metal detectors? What is a good entry level unit? My sons birthday is coming up soon and he has expressed an interest in doing it. Any help would be appreciated.

[KG4CGC]

Want!
What's your budget? A really nice one can be had for 5 bones.

[NA4BH]

You trying to get rid of one?

[KG4CGC]

You trying to get rid of one?

No sir, sorry. I am not. I have been studying them on and off for the last 8 years. One of the greatest ground hounds I ever met, found a large bore mortar near the beach at Myrtle Beach a few years ago. It didn't make the news because being ex military, he knew the stink it would raise if he went to the popo with it not even considering the rectal exam they would have put him through.
His level of circuit discrimination surpassed even the best amateur extra who made a career out of electronics RF and otherwise except for Fred.

[W4GPL]

I prefer the x-ray scanners. Giggity.

[K7SGJ]

I've had a White for years. They have some good entry level stuff, and some nice high end stuff, too. The thing I like about them is you can swap out the coils to match the soil condx, and the type of treasure you are looking for. They also hold their resale value if you want to upgrade. I really like mine.

[N8YX]

I've had a White for years. They have some good entry level stuff, and some nice high end stuff, too. The thing I like about them is you can swap out the coils to match the soil condx, and the type of treasure you are looking for. They also hold their resale value if you want to upgrade. I really like mine.

Gets a +1 from me if you're going to buy commercial stuff.

One of the greatest ground hounds I ever met

...snip...

level of circuit discrimination surpassed even the best amateur extra who made a career out of electronics RF and otherwise except for Fred.

What you did there...we're going to turn it into a teaching moment.

Why not build a detector from scratch and learn some RF theory in the process?

Simply put, a metal detector is an RF oscillator. The coils in the detection head make up the "L" in an LC network and the "C" can be fixed, tunable (manually or electrically) or switchable. The LC network is the tuning portion of an RF oscillator (Colpitts, Hartley, pick your favorite) and its output is processed then compared to a reference. A disturbance in the field (metallic object near the detection head) causes the resonant frequency to change and thus the output of the oscillator relative to its reference...which can then be observed on a meter or heard in the gadget's speaker or headphones.

Many designs get far more advanced that that. The "discriminator" variant can discern treasure from trash.

Here's a good explanation of the differences:

http://www.hobby-hour.com/electronic..._detectors.php

There are a metric shit-ton of circuits for these things on the 'Net. Wanna try rolling your own?

[W7UUU]

I have a White's Spectrum I've used exactly TWICE since new... wanna make a deal?
It was around $1000 new....

Dave
W7UUU

[al2n]

The Bounty Hunter Lone Star is a decent detector. You can get one for 150-200 dollars. Not too fancy, but with enough features to get the job done.

[NQ6U]

Metal detector: