Jump to content
Sign in to follow this  

Recommended Posts

Also called RF detectors and depth multipliers.  Invented in the 1930's by Gerhard Fisher (founder of Fisher Research Labs, now part of the First Texas conglomerate), this type of detector seems to not have changed much in operating characteristics in 80+ years.  From what I've found there are still three competing models in production:  Fisher's current Gemini-3 model (now 30 years old) https://www.detectorprospector.com/metal-detector-database/fisher-gemini-3-r27/, Garrett's Treasure Hound Eagle Eye Depth Multiplier (quite a mouthful) which is an add-on to their aging GTI 2500 standard style metal detector https://www.detectorprospector.com/metal-detector-database/garrett-gti-2500-r44/ and White's TM808 https://www.detectorprospector.com/metal-detector-database/whites-tm-808-r38/ , a spinoff of a collaboration between White's and Discovery, another Sweet Home, OR company that appears to now be defunct. 

The Fisher unit, operating at 82 kHz, seems to be the most closely aligned survivor of the early design.  Garrett's 'latest' depth multiplier (easily the most expensive at $1300 retail when combined with the GTI 2500) with its 7.2 kHz operating frequency advertises its advantage of being in the VLF range, ignoring ground minerals. White's unit (operating frequency = ?) has ground cancelling controls.  Unlike today's deep PI's and ZVT which can also go deep, these 2 box transmit/receive (T/R) detectors ignore small objects -- an advantage when the sought after target is large and in a trashy area. 

That's a brief overview of the current commercial climate, but what I'd like to know is how much different these three units are when it comes to operating characteristics.  Specifically do the differences in operating frequency and/or ground adjustments translate into better performance under certain conditions?

 

  • Like 1

Share this post


Link to post
Share on other sites

I can’t claim to be an expert on two box detectors though I sold quite a few. The only one I ever used was the Gemini 3 since I was a surveyor for a few years and they were pretty standard fare in a lot of survey rigs due to the ability to separate the transmitter from the receiver and the line tracing option. They also seemed to be the model of choice for the “treasure hunters”. Seems like most of the Gemini units I sold were headed to Mexico to look for lost treasure.

 

Important note: The chart and depths quoted below are based on optimistic low mineral conditions. Real life results will probably be less impressive.

whites-tm-808.jpg

fisher-gemini-3-two-box-detector.jpg

  • 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 LowTide
      It looks like C-Scope has something new on the Horizon.    What I found interesting was that twice in the linked video they make a point of showing the coil in saltwater, the second shot shows it being moved quite vigorously apparently to emphasize resistance to fals-ing.  Could this be a Multi-Freq or PI?
       
       
       
       
    • By rled2005
      I saw a White's High Sierra metal detector the other day for sale. I've never hear of that one. Looks like a very deep searching detector with no discrimination.
    • By kac
      The Coin Finder CF77 looks like a nice simple machine, has anyone here used one? Does it compare the Fors Relic?

      Nokta/Makro CF77 metal detector
    • By mn90403
      DetectorPro, the headphone company also makes detectors!  That is news to me.  I saw a guy in the dry sand with one of these waterproof detectors the other day.
      https://detectorpro.com/headhunter-12-underwater-metal-detector/
      I kept looking and chatting with him and there was no control module on his belt or on the shaft!  I looked at the waterproof headphones and there are extra knobs.  Imagine that, a headphone company puts the detector module in the headphones.
      Ok, I probably missed when these came out and the other models.
      How do they do?  Who has given a review?
      https://detectorpro.com/all-metal-detectors-2/
      Mitchel
    • By rled2005
      What is White's DFX Spectrum worth these days? Is it worth the effort to learn? Does it have a place with today's detectors?
    • By calabash digger
      What is this Deeptech VISTA X ???
×
×
  • Create New...