Sometimes these old machines can pack a punch !! More Information needed , Please !!!

[amtech2005]

Here are two files I got from someone a few months ago who has been on the forums for sometime !!!!

Definitely worth taking a look at . We need the full article of the kits that were sold , asking for anyone's help .

Here are the two files from 1977 and 1974 , that I was sent .
Regards............Eugene

[amtech2005]

Pack a punch , probably not !!!! I believe the first one from 1977 is a 10 khz 17 transistor 1 fet . Which was good for the 70s . The second project from 1974 is called a Phase Readout Gradiometer 7.2 khz inductive balance may have been good in the 70s also . We just want some more information . If anything these files can be moved to the Geotech Archive on the other pages .

Regards.........Eugene

[Altra]

I was always interested in the Phase Readout Gradiometer. Before PI's became popular this detector was used in saltwater hunting. Apparently when adjusted right it could ignore salt interference. Charles Garrett mentions it in a few of his old books. Attached is the patent with a full schematic of unmarked components. Maybe someone can modernize it?

[Altra]

Link for patent https://docs.google.com/viewer?url=p.../US3826973.pdf

[Qiaozhi]

Link for patent https://docs.google.com/viewer?url=p.../US3826973.pdf

You must have a gmail account to download the file.
Why can it not be attached here? Is it too big?

[Qiaozhi]

I managed to find it with Google. Please find attached.

[Altra]

For some reason my copy is 6.5mb? Also my return key does not function when posting?

[Tepco]

Strange, my version is only 604Kb long and apparently better quality, freepatentsonline.com uses better compression?

[Gwil]

Re post #7: My return key stopped working. But now it works again. I have no idea why.

G

[Qiaozhi]

Strange, my version is only 604Kb long and apparently better quality, freepatentsonline.com uses better compression?

As this patent appears to be a scanned document, the size will depend very much on the number of dots-per-inch used during the scan. Also, the one I downloaded is in Letter format, whereas your download is a custom size that is slightly smaller than A4. I've overwritten my local copy with the one you downloaded because of the better quality.

[technos]

These machines would not have been "kits" (in the traditional sense). The ECE BFL BFO 1977 machine was in the era and very sunset of the BFOs. And I pretty much doubt that the target ID really worked very well (they never did on BFOs). There were dozens of small manufacturers making them at the time as they were easy to understand and straightforward to make.

The 1974 PRG on the other hand is probably the father of the modern VLF machine. I can't help but wonder if the Whites or Garretts possibly infringed their patent with their early VLF machines. An interesting ad and schematic was poted in another thread in this forum (discussing simple machines primarily).

[technos]

If you haven't seen them in the Compass nabble forums forums there are these comments;

....in 1974....my DAD decides to upgrade from the Garrett BFO and gets the PRG.....PHASE READOUT GRADIOMETER....BASICALLY IT WAS A TR WITH A TID METER.....at this time only the very basic discriminators were being introduced to the Metal Detecting Community.....so this was a major improvement to anything else being used at the time....it would be 1980 or 1982 before anyone else would come out with the VLF TID detectors....I filled a metal pot (that was also dug up)...full of silver coins mainly silver quarters and silver half dollars......found a lot of gold rings...silver rings....and many silver and brass medals and insignias .......it was weatherproof which was another major innovation at the time....it would detect to maybe 10 inches on a silver quarter but the TID meter was only accurate to 6 inches or so....I had a few techniques where I could tell if the target was deep ....found some historic items also......(...I sold most of the above years ago..)..this detector was years ahead of its time...and today it is very rare.....the Manufacturer has stated that only a few hundred were made....BUT THE DEALER WHO WE BOUGHT IT FROM SAID THAT ONLY 50 WERE MADE..........in almost 7 years of searching I have Never seen one on FeeBay...although I have tracked one down using the old investigation methods the current owner is refusing to sell....I hope one day to be able to get it back...............

[technos]

And this comment;

The Phase Readout Gradiometer, or PRG, which was a TR-IB designed by a group of NASA engineers and marketed by Technos Inc.of Maitland, Florida (still in business) for hunting the wet salt, non black sand/low mineral Florida beaches. It was a straight shaft with a meter on it that measured Target I.D.; this was around 1973, and did so in a completely different method than today's TID units. It did not have ground balance capability, or autotune either, and this was several years before George Payne would patent the synchronous phase circuit we know as motion (George also submitted a patent in '78 for a discriminating time domain detector). The PRG cost around $900, this at a time when a top of the line detector from someone else cost about 1/3 of that, and BFO's were still being used by a great many people and it was the only detector you saw prospectors with. The search coil looked like two bowls used for feeding a dog, one upside down and the other atop it; at its widest in the middle it was around 10" and, from top to bottom was about 8" tall, and it would hit a quarter around 12" deep. It had an unusual tuning procedure it recommended, and worked by tone. You first get it to give a low tone on iron and everything above would give a high tone; you then repeated the procedure with a pull tab giving the low tone, and you then disregarded the low tone and dug only the high tone after looking at the meter to see the if it was a target you wanted; it read from 100 down to 0. Now it still continued to identify everything but you had to monitor the meter for all of the low tones to see where they read out if you were interested in nickles/rings. It was also heavy and difficult to read the meter, and depth decreased rapidly with an increase in ground minerals.Teknetics led to its demise with first the 9000, and then the 8500, and White's was right behind them with the 6000Di.
But we will never know where we would be today if this design had continued to evolve.
Maybe one day it will get a second look.

[technos]

An interesting thought experiment I like to do is ask whether you could take the 16 transistors and accomplish a better, higher performance detector circuit or not.

[Davor]

It is state of the mind that drives you to employ transistors/op amps/micros but at the end it is the set of building blocks that do the trick, as often emphasized by mikebg. You can do more with less, but market is a place where doing less with more often pays better, so there goes your incentive. Your IP is kept secret much better if you shove a few programmable devices in, without any other practical reason.

It is perhaps time to demand energy efficient solutions. If you observe state of the art, in fact state of the whole art of electronics, you'll see one winning gene of evolution: energy efficiency. It is linked with reliability, availability, ergonomics, autonomy etc. Less is more.

As for 16 transistors, deemon prefers transistors over other solutions. I tend to prefer whatever leads to a cleaner design.