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Re: Ground penetrating radar?
Posted by: JJames1610
Date: September 25, 2017 05:37PM
I have tried many detectors from just about all the makers of detectors. Including whites, Garrett, xp deus, deeptech vista, fishers, a lot just trust me. To go as deep as i need to go, you have to hunt in all metal, no discrimination, and cranked up. Its the only way to get deep enough on a larger target, i know because i have test targets from 1 to almost 4 feet deep. Problem is when you do set them up this way they pick up every mineral and iron rock around. When you start to add enough discrimination to fix that problem, your depth just went also. Very frustrating. I had a Garrett 2500 with a eagle eye depth multiplier. I got a good signal sounded just like a metal target. Dug a hole about 4 feet across and 3 feet deep. NOTHING THERE. Took a long time to figure out it was picking up mud. The dirt went from dry to very wet under the soil. It sounded just like a metal target. If you doubt this try it yourself. In the summer when its dry start your machine up and start running it on dry land, then head to the edge of a pond where you can see the difference between dry soil and muddy. Go across it and see what happens, a good signal.
Trying to figure out if someone knows a detector that will ingnore ground minerals, hoping someone could come up with some serious suggestions. I appreciate everyone's input, thanks.

Re: Ground penetrating radar?
Posted by: Tom_in_CA
Date: September 26, 2017 08:27AM
Quote
JJames1610
....
Trying to figure out if someone knows a detector that will ingnore ground minerals, hoping someone could come up with some serious suggestions. I appreciate everyone's input, thanks.

Don't take this wrong, but if you got a false signal from "wet ground" (and dug multiple cubic feet to figure this out), then me thinks "ground minerals" are the least of your problems. I have used scores of detectors also, for over 40 yrs. now. And regarding the Garrett 2-box set up you were using when you got the false wet-ground signal: While I can't say I've used that exact one, I have had experience with the TM-808. Which would be similar. And while you might get drift and flutters over anomolies (wet ground or whatever), you should have been able to tell the difference between THAT and a true target.

So I think you are mis-interpretting something in the audio, or are in some way not using it right. Without being there, I can't diagnose the particular issue. But just saying, that soil going from dry to wet will not cause a signal that the user can not discern via experience, audio, etc.....

Re: Ground penetrating radar?
Posted by: MI-AuAg
Date: September 27, 2017 10:12AM
Question for you Tom. (or anyone else with any thoughts on the subject)

I've never had occasion to use a two-box machine, but, I've always had interest in what's out there.

One thing that's puzzled me about the TM 808, and Gemini 3. Both are utilized for the same purpose, yet employ vastly different frequencies. The TM 808 around 6 or 7 KHz, and the Gemini 3, way up there around 80 KHz if I am remembering correctly.
What are your thoughts about the huge difference in frequencies used between these two, for essentially the same purpose?



Edited 2 time(s). Last edit at 09/27/2017 10:22AM by MI-AuAg.

Re: Ground penetrating radar?
Posted by: Tom_in_CA
Date: September 27, 2017 12:05PM
dunno. I've always thought all 2-box detectors (since the earliest fishers) were essentially the same. Dunno anything about "frequencies" of them, and so forth.

2-box detectors are sort of in a camp all by themselves when it comes to measuring detector ability. Because NORMALLY a "measure of ability" (when it comes to detectors ) is sensitivity. Right ? But ironically, when it comes to 2-box detectors , you DON'T want a machine that is "more sensitive". So for example, if you hold a domino sized metal object *just right* for the TM 808, you can indeed pick it up. (although it's designed only for large-objects-at-depth). Well gee, if you start to make the TM 808 more sensitive to GO DEEPER, then ... gee, what if that starts to make is sensitive enough to ring loudly on domino sized objects, or even smaller ? IT BEGINS TO DEFEAT THE PURPOSE .

But anyhow, getting back to your original question: I dunno :rolleyes:

Re: Ground penetrating radar?
Posted by: MI-AuAg
Date: September 27, 2017 12:58PM
After asking the question, I was thinking, in the yrs. since I was looking at some two-box specs out of curiosity, perhaps the frequencies held in the cobwebs of my memory were off. I checked the numbers, gladly senility hasn't set in, YET. The TM 808 is 6.59 KHz, and the Gemini 3 is listed at 81.92 KHz. I think that's why it stuck in my mind, the huge difference.

I guess the mystery remains? Thanks for the reply!

avatar
Re: Ground penetrating radar?
Posted by: Mega
Date: September 27, 2017 09:44PM
Thats a very good question regarding the different freq's of these 2 machines,as mentioned the 808 is a LF twin box and the Gemini or TW-5 which i have does indeed run at a much higher freq,but both basically do the same job,may ask the question on Geotech why they are so wide apart freq wise,should get some explanation from the boffins.

Will recharge my batteries in the Fisher and take it out for a while over this coming weekend,dont use it much,but like too keep on top on using it.



Deus and Nexus MP main everyday detectors

Displays on a Detector are really the equivalent of relying on sub-titles,give me a Analogue machine anyday.

Some of my site specific use machines.
TDI Pro 20'' Mono
Nexus SE dual 9'' coil
Nexus MP 14x13
Fisher TW-5 twin box
Crossbow PI Coiltek 14x9 Mono
Mirage PI 5'' Mono
DFX 18'' Detech
T2 SEF15x12
IDX Pro 15'' Concentric
Arado120b
B1 and B3
Trident11 Extreme NEL Snake


Mainly hunt deep ploughed and pasture sites,trashy roman/saxon and celtic permissions.

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