D-Tex GCD (Ground Cancelling Discriminator)

[vlad]

It was 1982 and I had just moved to Memphis from Beaumont, Tx, and getting my connections set back up for dealing detectors. Sometime in the late '70's Frank Ball and Dorian Cook had left Garrett to take over D-Tex, that was on the verge of bankruptcy. They started out with two models, a 5kHz that used six 9 volt batteries, and a 15 kHz that used four, and they were not frequency specific. Basically modeled after Garrett's Deepseeker & Groundhog, but smaller boxes and the batteries plugged into the right bottom side angled up at a 45 degree angle with a cover. They also had a two speed auto tune fast/slow and the best shielded loops on the market-nothing caused interference except another detector of the same frequency, and they used Garrett loop connectors so they worked on Garrett detectors (Garrett later changed the pin number to stop that).I had met Frank years before when I went on a hunt with A.M. Van Fossen out of Houston, and the hunt was on one of the oldest U.S. Cavalry bases, Fort Clark Springs,Texas, last commanded by Col. Robert E. Lee, when it was ordered abandoned. (Later the U.S. Army would bring in Seminole Indian Scouts to this area to track the Apaches.)
It was a late weekend because I remember my Fisher distributor from Hickory Valley Electronics coming by shortly before to show me the new Fisher 1260. There was a treasure hunt scheduled north of Jackson Tennessee, and I met Frank at the airport with the new GCD. The detector used TR reverse discrimination, but then reversed that so the audio when you hit a target you would have normal audio, instead of the detector going silent over a good target and giving a sound over a discriminated out [discrimination pt. set by user] target. The selector knob for modes was setup for three modes: Scan Disc.
(normal TR), Analyze-GCD, and VLF non motion.The switch on the end of the handle was pushed left to over ride of the auto function of the GCD Analyze mode and make it faster; pushing the handle switch to the right retuned the analyze mode (or acted as a conventional mode change switch to VLF/TR if in one of the other modes, plus retuned them.) When in Analyze there was no all metal mode; you set tour disc. to whatever level you wanted and started hunting. When you got a signal you centered the loop over the target;after a few seconds a beep was heard and you slid the loop off the target without lifting the loop. If you got a signal you dug, if it was silent you left it. If you didn't want to wait for the auto Analyze sequence full time period, you pushed the handle switch to the left to over ride the time lag and moved the loop over the target, going by the same audio results as full Analyze. Pushing the handle switch to the right retuned the detector. If I remember correctly, putting the mode switch in All Metal or Scan Disc. turned it into a regular VLF/TR. The problem was that Analyze was a gimmick-every VLF/TR had TR reverse disc., but it was called reverse because once you located the target and hit retune, you slid the loop off and if it was silent you dug, and if it gave an audio you left it.(TR reverse was deeper than regular TR, but slow.) The reason it went silent is a good target is giving out an audio, but retuning you return to the threshold, the level you were at, which pushes it silent. A discriminated out target makes the detector go silent, so when you retune the null is brought up to threshold, but sliding it off makes it loud because the retune brought the null of the disced out target to threshold at that one point, any other place lacking that metal resulted in a full blast sound. Frank took out full page ads saying "MOTION IS DEAD-GET THE NEW GCD BY D-TEX.," and advertised it a lot-to no avail.
I bought that prototype but immediately noticed a problem. In my test bed it would not hit the deep coins in Analyze or TR. I called him up and told him, and he said in the lab the 5" co-ax would match the 8." I said you have two problems; its too small and its a co-ax (the D-Tex regular 5kHz loop wouldn't work on it.) not a concentric That call resulted in an 8" concentric for all GCD's. But within 12 months a new mode was added to the GCD, a 4 filter motion mode. You can't beat the market. Shortly thereafter when I was back in school at Lamar mine quit working and I sent it in. They called me up and offer me a new GCD with motion for $50 in trade which was hard to turn down. Maybe they wanted it for a museum, I'll never know-but they were out of business in three years-never offered 2 filter, or TID.
(A few years later they were back making a licensed improved copy of the Fisher 1265X which you could lock in either disc.1 or disc. 2)


http://treasurelinx.com/uploads/detector05.jpg

 

[JoeTex]

....Vlad......I found a D-Tex Coin Shooter GCD Motion Plus at my local Flea Market.....it is the hip-mount model with the LED for Coin Depth and for the Battery check......the control box looks like the same ones that D-Tex used for their Search King series.....this may be the last of the GCD series that I know of ??.... this detector has a few problems but I plan to on getting it repaired soon......I found a D-Tex 5 inch Omni coil which should work good on this model......I think that it is Ironic/Uncanny that the GCD series was the one that Frank Ball stated why Motion is Dead in their advertising campaign......this model shows that Motion is Not dead since it has a Motion circuit mode !!....Anyway I think that it is Neat and this is one of the ones that is a Keeper ....no matter if it works or Not......Joe

 

[Tom_in_CA]

Vlad , thanx for the nostalgic look back, and a little "behind the scenes" history of that. I remember seeing those in the magazines at that time. And go figure, in those days pre-internet, magazines or hearing-from-your-buddies was the only way to have contact with the out-side world. Not like today where you can just get on-line and see the pro's and con's buzz talk from various places and people. Back in the older days, you were at the mercy of glitzy magazine ad claims.

Yes, some people did buy it based on the claims of ability to supposedly get motion-disc. depths WHILE NOT having to swing fast (or motion at all, or whatever). And while that's laughable now, yet you have to put it in perspective: At this time (very early '80s) the motion discriminators then on the market were VERY fast swing machines. So the prospect of getting away from those golf-swing speed monsters, was inviting enough for some to invest and try it. No one could argue with the depth that 6000 and 6dbs were getting, but no one liked to have to "whip" the coil either.

And the end result was exactly as you stated: The machine had problems measuring up, and never really did as promised. Within a few years though, various manufacturers had slowed the swing speed way down though, so it eventually all became a mute point.

Great nostalgic look back. Thanx !