Possibly the best detector ever made that operated very differently than todays detectors ceased production-who knows where we would be today with an

[vlad]

It was initially designed by NASA engineers to hunt Floria beaches for Spanish ship wreck coins and built by Technos Inc. It could do something the best discriminators
today can't do-accurately separately coins by denomination, and it did this in 1972. The search coil looked very different, like two round pet bowls for water,
one sitting upside down atop the other.[an axial gradiometer consist of two magnetometers placed in series, one stacked above the other. The result from it is the difference
in magnetic flux at that point.] How this was incorporated into a metal detector for finding metal I don't know. It could hit a quarter at 12" in neutral soil, but the more mineralized the soil caused constant tuning, and utilizing the readout to i.d. targets, and lessened depth. Probably the biggest cause of its demise was cost; when top of the line detectors from other companies sold for $300, it sold for $900. But had it stuck around, with constant evolution, metal detectors as we know them would be quite different. [why I'm looking to buy one]

Thanks to Ty Brook who wrote the Tech Talk column for many years for much of the information.

 

[Tom_in_CA]

I've heard of this machine. Basically an early attempt at TID's conductive scales. Not a difficult concept, when you think of it. Because already, at the time, in 1972, there was already ascending/descending knob disc. machines (albeit primitive, and disc. was still a novelty at the time). And if conductivity disc. settings could be increased or decreased with the turn of the knob, then ..... in effect, a person could attain a form of TID, just be checking targets over and over again, to see where the target ceases to be heard. Ie.: the fallout point. And with that you'd know where on the conductive scale it was. The only thingthe PRG did, was automate that concept.

And no, it could not tell the denomination of coins. Well, at least no better than any machine today can. Ie.: any TID machine today can tell nickel, vs dime vs quarter, and so forth. But it's not really telling you "this is a quarter" or "this is a nickel", etc.... It's just telling you what the conductivity is (per the size ratios) of the targets. So for example, a car key may give an exact TID as a penny. A beaver tail off a tab my say nickel, and so forth.

Great nostalgic look back! thanx for posting about it.

 

[vlad]

Controls went like this. Using various controls one tuned the machine to allow it to distinguish between ferrous material,( 800Hertz-tone)
and nonferrous material (1100 Hertz tone.) The controls were then manipulated to make foil or a pulltab respond with the 800 Hertz tone so that it
would be ignored. Coins and other targets above this phase response would produce the 1100 Hertz tone, alerting the operator to the fact that a target had been
discovered. Then actual meter readings were used to determine the targets potential denomination. For instance a copper cent read about 80, a nickel about 48,
a dime at 79, a quarter at 90 a half-dollar at 93 and a dollar at 95.
Reading every target's position on the scale was a chore, as well as keeping it tuned. It was a TR-IB [not all TR;s were IB's]-no auto tune, ground balance, not VLF range,
and several years before George Payne invented the motion discriminate circuit.
Howeve it worked like no detector before or since.Hoprfully, someone could bring back this design highly evolved for our next leap in frequency domain detectors.

 

[John(H)]

....Basically the downfall was the price and only if you was an owner would you know that many of the meters failed after a few years and they were expensive to replace...luckily mine was replaced under warranty....it was loads of fun but did not get the depth of the VLF's in regular ground....the tremendous depths quoted are on Non-Black Sand Beaches in Florida....I never got the depths that were quoted.....and it was heavy......it would take both hands to use it if you hunted more than an hour at a time....me and my dad took turns with one operating it and the other digging....lots of silver coins found and copper pennies and other non-ferrous objects....but it did Not have the depth of the VLF's......Joe

 

[John(H)]

....Someone in the company destroyed all of their records so nothing has survived except the information from the Patent Office....even today they do not Not like to discuss the PRG....most probably were Not around.....since that was a long time ago ....42 years....that is a shame would like to see all of the info that they had on that detector......even tracking one down today is tough....it is basically detective work figuring out an original owner and the then because of the time factor have to try and locate family members who would know what happened to it since a lot of the original owners have probably died...........Joe