Gardiner 202A

Back in the late 60s early 70s when I was beginning to think about buying a real metal detector to replace my WW2 mine detector that I had been using since 1962, I often saw adverts in "Australian Post" for Gardiner Treasuretron C metal detectors. They were around 700 dollars so were beyond my concideration.
Anyway about two three weeks ago a Gardiner 202A came up for sale on Ebay and this triggered some early memories and I decided to find out whether the Gardiner detectors were actually capable of detecting gold.

I scored the 202A and it turned out to be in pristine condition and had belonged to a chap in the states who had flown and survived 52 missions into germany on B52s during WW2.

It arrived with the original sale receipts and catalogue and instruction manual.
After reading the manual I had learnt that it was one of the first GB/VLF Discriminators and had some interesting features like:
temperature compencated ccts and components, A fixed Disc mode set up for yank coins, A coil cable that runs down inside the shaft and a Plug in coil, the cable plugs into the coil at the coil. it runs on a single 9 volt battery and one AA. The 9 volt is said to operate the detector for more than 100 hours and the AA will last as long as the shelf life of the battery.
The received tone is like a VCO tone that rises in pitch as the target signal strengthens.
The detector can be set to fast auto re tune or manual push button retune.
There is an signal strength/Tuning/battery check meter, an internal speaker and a decent set of HPs with a 6mm plug and socket. The stem is a two piece unit with a hand grip just forward of the control box.
At first glance this seems to be an awkward set up but in fact is pefectly balanced although the the box is behind the operator elbow making access to the controls a hassle but yet again, once the detector is tuned and ground balanced it stays that way with little need to fiddle with the controls unless changing to the disc mode and with this detector I doubt that I would be using disc very often.

The detector is a VLF but runs like a cross between a vlf and a BFO.
The manual states that the detector will handle salt, black sand and iron mineralisation.

So in went some batteries and switched her on and she burst into life like it was new and out I went to my test patch in mild iron ground. After setting the machine up as per specs I discoverd that the thing was so smooth and stable that it didn't even need ground balancing to the extent that at first I thought it was not detecting, but it was and found all of my coins at 8 inches (Just). Then I tried it on some small nuggs and no kidding folks this machine will detect gold down to 0.05gm and found one of my 0.2 gm bits at 3 inches in the ground no problems.
The disc mode is OK for silver brass and copper; The threshold goes quiet on iron and rusty metal and some fairly large gold rings and all Aussie decimal coins except 1 & 2 dollar coins.

The threshold of this detector is absolutely rock solid stable.and even with the GB way out of adjust it still found my test patch coins.

I did a field strength measurement on the coil and it is very weak compared to machines today and I am a bit baffled as to how the detector is so sensitive to small targets within 6 inches of the coil..
I have absolutely no doubt that this detector would perform very well on the mullock heaps.

The coil (6 inch) has electronic components within the coil housing and so I was not able to obtain any inductance readings of the windings.
This detector is clearly not a pure VLF/TR or BFO, it is a bit of a mystery that works very well and I am happy that I purchased this item and satisfied a memory from a long time ago.

G'day Adrian

That sounds like an interesting purchase mate, let us know how it goes out in the field and on mullock heaps when you get a chance.

It also sounds like it has some very interesting technology incorporated into the machine and the coil especially for it age, amazing.

cheers dave

Hi Adrian
I know that one of the things thats been on the agender lately with detector design is the front end saturation control such as the one woody does at the moment.Having the weaker transmit may help in eliminating the ground mineralisation.The other thing you mentioned was the amplifier in the coil,this is like the sovereigns giving them less interference sort of like a masthead amplifier giving a higher signal to noise ratio.It doesn't surprise me that in the process of pushing for depth and all round detectors there's still a place for these earlier detectors with their sensitivity to surface targets.
Thanks for an excellent post I,m sure this will be of interest to many people.
Steve

The TX signal is from this old detector is not just weak, it is nothing short of feeble.
Where I can measure the field strength from my Infinium, LST, SOV, Scorpion out as far as 20 feet from the coil,
The field from the 202A is not detectable by my meters at 4 foot but in close to the coil it is strong.
I have not taken the detector into the field yet but have subjected it to most of the tests that I have applied to my other machines and the All Metal mode has an excellent GB range that easily smoothes out the effects of some large solid iron ore samples.
I ground balanced the 202A over a 2.5 kg slab of iron ore with ease and then placed a 0.5gm nugg on my flagstone pavers and placed the iron ore slab on top of the nugg, the detector responded to the nugg easily and with just a little of the usual threshold boinging that you get with most auto tune vlfs on hot ground.
I thought that the GB range would not be wide enough on the iron ore but there was plenty of adjustment to spare.
The GB has two controls, a course and fine adjustment. The course adjustment is a tad touchy but is consistant in operation and the fine adjust realy gets the GB accurate.

I am going to enjoy trying this old detector in some gold fields when the oportunity arrises.... It has been a bit of an eye opener to date.

Well I have not been out in the field yet with the 202A due to the crap weather lately but I have run a few more basic tests and I can say that the Disc mode is not at all usefull and that if the detector ever signals a target in this mode it is a fair bet that it will be a goodun and probably sil, copper or very large gold ring, everything else gets disced out inc some pretty heafty gold rings.

The All metal GB mode is very good but not deep at all, although the coil is only 6 inch.
The detector is very good on small sub gm nuggs and fine gold and sil chains. It even responds to gold foil.

I have some fine gold chain that my scorp picks up OK, the Super traq struggles and the Sov won't signal on at all but this old timer detector picks em up like it was designed to do exactly that. The machine handles some fairly significant iron ore and even tho it does not get a lot of depth I am certain it would do well on the mullock heaps where the small gold is. It runs a very suprisingly smooth threshold.