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B.. Just what was a "Metal / Mineral Locator" I spoke about?

May 07, 2021 10:03AM avatar
Most of the popular devices we had from about 1964 and into the early '70s, both BFO (Beat Frequency Oscillator) and TR (or T/R for Transmit / Receive), were called 'Metal / Mineral Locators'. They had a control knob labeled 'Tuner' which was used to properly 'tune' the detector for peak operation, and you adjusted the 'Tuner' control clockwise or counter-clockwise for either 'Metal' or 'Mineral' based upon what type of metal category you wanted to 'Locate'. It was very simple.

The 'Metal' direction was for Non--Ferrous Metals, such s silver, gold, copper, aluminum, foil, lead, etc., etc., The 'Mineral' direction was for Ferrous or Iron Metals, such as nails. bolts, screws, washers, steel rods, and almost everything in the magnetic class of ferrous-based objects.

How to properly 'Tune' a metal detector. First we had to understand that there were two operating principles used: BFO and T/R, and they operated differently. (Note: I may use either TR or T/R in this nd future descriptions.) Here's the difference:

BFO ... The Beat Frequency Oscillation design is a Frequency Change design, and to properly 'Tune' the detector, you adjusted the 'Tuner' to hear a 'motor-boating' sort of 'putt-putt-putt' to an ideal 'putting' speed for that detector. Most models featured both a Metal and Mineral Tuner direction so if you were Coin & Jewelry Hunting, you adjusted the Tuner towards 'Metal' to get a good, functional, 'putting' to listen to. When the search coil was moved over a desired non-ferrous metal, such as a coin, token, copper thimble, lead bullet, and so forth, the 'putting' or 'beats' would increase which was a shift in the Frequency. You pinpointed at the highest pitch and recovered your target.

If you swept the coil over an Iron Nail or most rusty washers or other ferrous-based metal, which would be considered a 'Mineral' class target, the 'putting' you were listening to would slow down and diminish. Become silent. That was your 'audio classification' that you encountered an undesirable piece of Iron trash.

T/R ... The Transmit / Receive design is a Loudness or Volume Change design, and to properly 'Tune' the detector, you adjusted the 'Tuner' control to hear a slight audio 'Hum' which is adjusting to the 'Threshold' of sound. You didn't adjust the Tuner to be silent or to be loud. Only to the where you're at the comfortable 'Threshold' of hearing an audio 'Hum'. If you swept the search coil over a non-ferrous object, such as a coin, token, thimble, button bullet, etc., you would hear an increase in Loudness or Volume as the center-axis of the coil was positioned over the located object. Then you recovered it.

If you were listening to a good working Threshold audio and moved the coil over an Iron Nail or Washer or other ferrous-based metal, the audio 'Threshold' would diminish to even become silent. That was an 'audio classification' you encountered an undesired Ferrous object and could ignore it.


NO, not all ferrous-based junk was going to produce a nice-and-proper rejected audio when we were Coin Hunting, but most did. There were, and are, some bothersome pieces of trash we had to live with, but it was nowhere as annoying as it is today with our so-called 'modern' digital circuitry designed models.

By the early-to-mid '70s we generally moved away from models with a Metal / Mineral Tuner and the units were only tuned to respond to Non-Ferrous objects which was good for the bulk of the detecting Hobbyists who were Coin & Jewelry Hunters. We also saw the change from calling them Metal / Mineral Locators to simply Metal Detectors. And, for the most part ,we continued calling a 'Tuner' control just that until we got into the mid-to-latter '80s when the popular trend was to rename that a 'Threshold' control, which is exactly what the 'Tune'r' was supposed to adjust for.

For those who haven't understood what that original term was or how the two basic types of detectors worked, I hope this might have helped as we continue on our pathway to learn more, hunt better, and deal with that blasted ferrous junk out there.

Naturally, as this closed thread continues, if you use your detectors and have any questions, or are a little lost in something I've posted here, simply shoot me an e-mail to either address below.

Monte

"Your EYES ... the only 100% accurate form of Discrimination!"

Stinkwater Wells Trading Post
Metal Detector Evaluations and Product Reviews
I'm now located in Clyde, Texas
monte@ahrps.org ... or ... monte@stinkwaterwells.com
503-481-8147
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Edited 1 time(s). Last edit at 05/07/2021 06:26PM by Monte.
Subject Author Views Posted

Now we are going to take a stroll out of the urban trash.

Monte 296 May 06, 2021 10:46AM

F.. We have now arrived at Iron Nails and Rusty Tin ... What to Use and What to Do?confused smiley

Monte 115 May 14, 2021 02:37AM

E.. Problem Common Trash; so-called 'False Signals'; Useful Search Techniques.

Monte 132 May 11, 2021 06:26AM

D.... The next major advancement: VLF-Disc. and Motion-Discrimination.

Monte 113 May 09, 2021 09:22AM

C.. And then came the Discriminators, and VLF's and VLF/TR-Disc.

Monte 88 May 07, 2021 06:27PM

B.. Just what was a "Metal / Mineral Locator" I spoke about?

Monte 97 May 07, 2021 10:03AM

A.. First, let's follow the path that leads us into various Iron / Ferrous debris.

Monte 166 May 07, 2021 05:08AM



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