Jump to content
Sign in to follow this  
aufarmer

Fisher Gemini 3 For Prospecting

Recommended Posts

Just curious if anyone has had an experience using a Fisher Gemini 3 or similar detector in prospecting trying to find an ore vein.

fisher-gemini-3-metal-detector.jpg.9c58d
Fisher Gemini-3 Two Box metal detector

Share this post


Link to post
Share on other sites

I have not but I am familiar with the Gemini-3. To bring others up to speed I added a link to your post for more info on the Gemini-3.

These "two box detectors" can be used as an integrated unit connected by a rod. These detectors are in effect a very large coil and can only detect objects about the size of your fist or larger, but at great depths depending on ground mineralization. These are induction balance detectors and a large coil pulse induction model may work better in severe soils, especially on objects that are small enough to be borderline targets for this type of detector.

However, you can also use the transmitter and receiver separately to create a larger search field, that can be used to look for large hidden bodies like large veins or ore deposits. This is what Fisher calls a Wide Scan Inductive Search on page 12 of the Fisher Gemini-3 Operating Manual:

Wide Scan Inductive Search

This mode of operation is the preferred method for searching a large area quickly. Two operators are required and the handle assembly is not used.

The Wide Scan Inductive Search mode is practical only when searching for ore veins, pipes or cable 40 feet long or more. If the  operators are too close together, “direct air coupling” will result, meaning the receiver is detecting the Transmitter signal directly through the air instead of through a buried conductor.

fisher-gemini-3-wide-scan-inductive-search.jpg
Figure 7 - Wide Scan Inductive Search

Set Up

Two operators line up at least 20 feet apart, one with the receiver and one with the transmitter, parallel to the assumed direction of the buried conductor. The transmitter and receiver should be in line with each other, facing the same direction.

Tuning

1. Set the transmitter: Power: ON

2. Set the receiver: Power: ON Sensitivity: ZERO

3. Slowly increase the SENSITIVITY control until the audio signal is heard, then reduce SENSITIVITY until the audio just disappears. This is the point at which “air coupling” has been eliminated.

Operating

1. Keeping the receiver and transmitter sections in line, the two operators can now walk their predetermined search pattern. The SENSITIVITY control should be checked periodically to ensure that the receiver is tuned just below the “air coupling” threshold.

2. If both operators cross the same conductive body (pipe, cable, ore vein, etc.) at approximately the same time, the receiver tone and meter will rise to indicate its presence. The receiver operator should alert the transmitter operator that they have detected a conductive object.

3. The receiver operator should then hold his position while the transmitter operator moves back and forth for the strongest receiver response. At this point, the transmitter operator should stop and place the instrument on the ground with the handle grip on top.

4. The receiver operator can then pinpoint the buried object by moving the receiver back and forth in line with the transmitter. The object should be directly beneath the point of maximum response.

5. The receiver operator may then trace the signal along the length of the unseen object as described in the Inductive Trace section (page 12).

The methodology above describes looking for a pipe or buried fuel tank. You can however find a very detailed expansion of the subject as regards prospecting on pages 46 - 52 of the Handbook of Geophysical Prospecting Methods for the Alaskan Prospector under the heading "Electromagnetic Methods". This publication is an older one but this type of detecting is even older, dating back to the original two box Fisher Metalloscope of the 1930's. The booklet is written for the practical layman prospector and so describes several geophysical prospecting methods in a relatively understandable manner.

See also the discussion starting on page 4 of Geophysics For Mineral Exploration - A Manual For Prospectors for more up-to-date information on the subject.

  • Like 6

Share this post


Link to post
Share on other sites

Interesting topic and thanks for starting it and Steve's reply,i own and use a Fisher TW-5 which is basically the same machine as the Gemini-3 model,only use it as has been suggested on the supplied rod that is suspended from the shoulder by the provided strap.

Alas as we dont in 'theory' have gold in its raw state here in the UK i cannot comment on how it would fair for gold nugget hunting or gold detecting in general,how i use mine is for locating the deep container ie hoard or deep artifact/s after i have located what i suspect is a potential scattered hoard ie the top of a container that has been clipped by a piece of farm machinery usually deep ploughing,this then drags up some coins from the top of the pot/container and scatters the coin in a dragging fashion by further ploughing.Once i have located such a coin scatter then its time to use a twin box in this case the Fishers.

My twin box does not come out too play all that often but is the ideal detecting machine for the job in hand,of course its totally useless for locating single coin size items,but i am not after those as i am after the 'holy grail' the pot itself.In the new year hope to be back on a potential celtic gold stater hoard site,we have located about 20 full staters all in a very tight radius and all the same style,so it ticks all the boxes for a possible container location rather than say a purse drop.

  • Like 5

Share this post


Link to post
Share on other sites

aufarmer

We used to use my Gemini 2 box with a high sens setting to find black sand concentrations along creeks. We would set up our dredge up there with fairly good success.  Should work better for high banking. rh0dium

  • Like 2

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Similar Content

    • By calabash digger
      What is this Deeptech VISTA X ???
    • By phrunt
      Well, after reading JP's review on the QED followed by Reg and Northeasts review and the occasional QED user popping up I decided it's time to get one.  I didn't need the full package and was on a budget so bought a new one but without the 11" coil it comes with, also with the different shaft more like my Gold Bug Pro shaft.  I'm quite used to that shaft style and like it.  I'm yet to get my wireless audio kit for it, I ordered the Quest Wirefree mate kit from Phase Technicial yesterday. It's meant to be good for the QED but I'll use it for my other detectors too, it can make any detector wireless using 2.4Ghz, nice fast audio.   Once that arrives I'll be completely wire free from my QED. 
      The QED feels so light, super easy to swing.  It's just using 2 x 18650 batteries so really there is just no weight to the detector at all, the only weight I notice is the coil.  I was surprised how small the control box is, it's tiny!

      On the floor next to it is my little Sony speaker, it's powered by 2 x AA batteries and makes the audio nice and loud on the QED until I get my wirefree kit and then I'll start using my Steelphase SP01 booster with a SPK08 GME like I use on my GPX, only difference is I won't be tethered to my detector.
      It was raining when it arrived so I played around inside with it.
      I fired it up and was surprised, even inside my house it was hardly bothered by EMI at all, I adjusted the Threshold B to suit the coil, simple to do, move the numbers down until it makes noise, move it up until it makes noise, in my case down went to 48, up went to 58, here you can either favour smaller targets by going to say 49 or 50 or you can favour larger targets by going to 56 or 57, or you can leave it smack in the middle at 53 for an even balance between both.   That's why understanding anyway, I'd hope some experienced QED user would correct me if I'm wrong.   As our gold is mostly small and the only gold I have to test it with is small I settled on 50.
      I then moved my gain up to 10 (the maximum) and it was running nicely, even inside my house there was very little false signals.
      The QED has a mode as well, between 1 and 16, 1 for mild ground and is more sensitive to small gold, up to 15 for mineralised ground, and 16 for the beach.   I of course wanted to be in 1.
      Still the QED was running pretty quiet inside my house, very little false signals at all,  my house is full of EMI, a very powerful long range WIFI router and all the usuals, plus my house is only a short distance to high voltage power lines coming from some Windmills.  To be able to run the QED maxed out inside with minimal issues shocked me.
      I tested my various coils on it including the 12x6" X-coil which ran like a dream, then the Coiltek Joey 10x5, and the same settings as the X-coil and worked just fine.  Then the Nugget Finder EVO 14x9 was installed, I had to adjust my Threshold-B after installing this coil, so moving the numbers down till noise, then up till noise then picking the spot you want it... no big deal, takes about 20 seconds even for a first time user.
      The EVO had a bit more falsing inside due to it's size I guess, lowering the gain down to 7 from 10 fixed it up, tested with a shotgun pellet and the depth difference from gain of 10 to gain of 7 was hardly noticeable.   The other thing i tried was moving off Mode 1 onto Mode 5 and then I was able to run at gain of 10 again with very minimal falsing.  I was getting between 1 and around 2 inches on shotgun pellets with all coils I tested in an air test.
      The rain stopped so I headed away from home to a more remote location (3 minutes drive) away from the EMI of my house and put on the X-coil.  Now it was completely silent, not a peep from the detector unless I went over a target.  I ran on it on the default threshold which is silent, I turned the threshold up and found I had a nice smooth threshold but I was happy with it on silent, It was like using my Gold Monster, only noise if there is a target,  On my basic tests it didn't seem to hinder it's performance running silently but I'll test further in the coming days.
      The QED has a default ground balance of 100, I didn't need to do a ground balance, I could raise and lower my coil all I wanted with no noise, Auto ground balance didn't do anything as it was already balanced, I ended up lowering my ground balance to 70 manually and it was still silent pumping my coil so I just left it there, I tried as low as 50 but noise started to come in then so 70 seemed a good spot.  This is where I will differ from a lot of people so take into account my ground is VERY MILD so my results will likely be different to someone in higher mineralisation.
      I tested over various nugget sizes and was pretty amazed by the results, it felt like I was using the Gold Monster, very sensitive to small gold, I was detecting bits as small as 0.02 of a gram, 0.04 of a gram was giving me over an inch.  A shotgun pellet was also over an inch, more likely 1.5 to 2 inches.  I wasn't accurately measuring of course.
      The small gold ability of the X-coil on it to me seems far better than on my GPX 4500.
      I could move around the ground and never get any false signals, nothing caused me issues, if there was a noise it was a target.  This was pretty good as I was running it in the settings I believe are maxing it out.  I might be wrong but that's how I understand it being a first time user.  To me it feels like a Pulse Induction Gold Monster 1000.
      The only negative I have is the audio without some form of amplification is too low for my liking, I like loud audio.  With the SP01 booster it's brilliant, with my Koss UR30 headphones plugged in directly  I found it was pretty quiet, although I'd never use them on it anyway as I want wireless.  Once I get my Quest Wirefree kit I am sure it will be resolved as that's a powered unit, I think anything powered will work well on it but non-powered speakers/headphones will be too quiet for me.  My little AA battery powered Sony speaker works great on it.
      Obviously I've got a lot more to learn and a lot more hours on it to be able to even consider leaving a review but these are my first impressions.  All the outdoor testing was done with my 12x6" X-coil, I hope the weather is good to try my NF 14x9 EVO and Coiltek 10x5 Joey on it tomorrow.  I hope this post makes sense...
      So far I'm very happy with my purchase.
       
    • By squirmingcoil77
      Hello all.  I was wondering if it's possible to customize the tones on the VX3.  I know you can assign tones to all the vdi #s on the V3i and even change the tone pitch on the XLT and DFX, but I did not see where you can alter the tones on the VX3.  Maybe i missed it in the manual.  Does anyone know?  thanks.
    • By Steve Herschbach
      Published on May 14, 2019
      “Hello all, hope you’ve all had a great weekend. We’ve just put a short video covering some of the aspects on the DeepTech Vista X together, some of the features that you’ll see in the video has been altered but we will be making a new video on these changes very soon. We’ve had so much interest in the Vista X, we put a video together as fast as possible to show some of these new features. Thank you for your patience, more information and update video on performance coming shortly. Recommended retail price: 580 Euro”

    • By Steve Herschbach
      Tarsacci MDT-8000 Data & User Reviews
       
×
×
  • Create New...