The Amazing Dave Johnson

From an article on the "Detector- Prospector" forum, by Steve Herschbach
List of metal detectors designed by Dave Johnson
Gold detectors highlighted in red.

Fisher in California: 1260, 1220, 1210, 1235, 1225, 1212, 1265, 1266, CZ6, CZ5, CZ20, original Gold Bug, Gold Bug II, Gemini, and industrial instruments including TW6, FX3, XLT-16, PF-18, and circuitry of the TW-770.

Tesoro: Diablo MicroMax, Lobo SuperTraq.

White's: GMT, MXT, analog circuitry of DFX, Beach Hunter and PCL-600 line tracer.

Troy: X-5 and X-3.

FTP Bounty Hunter: major revisions to existing platforms most of which originated with George Payne. The BH Junior, Platinum, Gold and security wand (sold under various trademarks) were new designs.

FTP Teknetics: T2, Alpha, Delta, Gamma, Omega, G2.

FTP Fisher: F2, F4, F5, F75, F70, new Gold Bug, circuitry of the TW-82 industrial line tracer.

What an amazing guy.

Hopefully, one day, Dave will put his brilliant mind to work and design a Gold Detector to rival Bruce Candy's swan song, the Minelab GPZ 7000. Minelab needs ( although doesn't desire), real competition! And if anyone can do it, surely it will be this man.
I know the American market doesn't need one, and that's probably why he hasn't made one. But as a final swan song, and just to finish his career at the top of the tree, maybe he might get around to it. (He ain't getting any younger)    Here's hoping.  

Fisher have not produced a PI since the Impulse which I think ended around 2000. It was an OK beach and scuba machine.
It would be good to see another competative PI from Fisher.
      I still have my 553D which has an excellent GB All metal mode and runs a silky smooth threshold. The Disc mode a typical TR discriminator but what I like about it is that it can Reverse dicriminate to the depth of the target if you are carefull to control the height of the coil above the target.
      This detector has located a lot of pre decimal coins in the disc mode from surface to around 10 inches deep and was my primary coin and relic detector untill I purchased the SOV.

Dave's all time favourite detector he designed is the Tesoro Diablo Umax .

He posted the following some time ago about using the secondary Ground balance feature on the Diablo Umax .

Many years ago, Ed Coogan taught me a trick for dealing with suspected hot rocks: you balance out the offending spot, which of course means you're no longer balanced to the ground matrix. Then you sweep over the spot very level and slow in different directions, listening carefully through the ground noise. A hot rock, usually you can make it disappear. A nugget, usually you won't be able to balance it out completely, you'll still hear it.

With other metal detectors, this is a time-consuming trick which makes it necessary to rebalance over matrix when you've given up on the hot rock. So few people use it.

In many areas, hot rocks will tend to be of a particular type, fairly consistent on their ground balance point. If you've got that kind of situation, with the Diablo uMax you balance over one of 'em (or a collection of several of 'em) using the secondary GB. Now you search in the regular GB mode but when you hit an anomaly you switch to the secondary GB setting to check the target. If it's disappeared or gives a very muffled response, it's probably a hot rock. If the zip is still there, you've got metal. And if you're lucky, it's gold.

--Dave J.

Yes I like the Diablo Gold demon and the dual GB feature.
I have a LST which although it has Auto ground balance it is reluctant to gb small gold. Hot rocks take one or two pumps of the coil and gb quickly whereas small gold down to 0.2g requires three to four pumps to tune down and even then the gold will not go completely quiet.

Fisher never designed a detector totally for gold detecting, other than the Gold Bugs which are still good on small shallow gold in fairly tough ground while still being able to find large nuggs at significant depth in quiet ground but being single frequency VLFs they will always be hindered in heavy iron mineralisation and hot rock conditions.

A new PI AQ Impulse detector is about to emerge from Fisher. First version for beach hunting, second version for nugget hunting with an expanded ground balance, plus they are making additional nugget coils, a larger battery for extended use nugget detecting, etc. The beach version is equal to the GPX Minelab in depth. Yet a lightweight detector! 3.9 lbs beach version.

http://www.dankowskidetectors.com/discussions/read.php?2,145750,page=14

http://hobby-detecting.com/fisher-impulse-aq-a-new-pulse-metal-detector-with-metal-discrimination-2019-novelty-first-photos/?fbclid=IwAR1M3tVtULxFnuYZtvIs4zbrYu_2NUDkrzvNM-LbRA_uiQzdN08pgMWl-48

Interesting to see how it stacks up against the GPX series for sensitivity/depth. Good discrimination on a PI unit is a welcome sight indeed, but not if the discrimination side drops off dramatically at depth. Interesting to see though. About time Fisher.

Cheers Kon.

AQ Impulse is supposed to find an 18" nickel same as gpx. Just some of what i read about it. Obviously quite a bit more power than a TDI. The big question is, once they add an expanded ground balance to the machine for nuggets how deep will it detect. Personally I am eyeing this machine for use for tiny nuggets to 2 gram gold at depth, hoping that the 7 usec timing will excell. The timing is adjustable for other uses.

Mineralization, or the amount of concentrated mineralization within any given area or section of ground, is & has always been a major drawback factor, for all past PI units (more so on VLF's) regarding depth over positive targets. If this newly designed & long overdue PI detector from Fisher, can replicate the penetrating power, of a GPX 5000, on or over a majority of various size/type ferritic/alloyed targets, then coupled to a good discriminator, as well as value for money, will be a winner. Can't wait to hear of some positive results coming back.
Looks like 2019 will be a good year for the introduction of new developments within the prospecting/metal detecting world.    

Cheers Kon

Kon61gold wrote:Interesting to see how it stacks up against the GPX series for sensitivity/depth. Good discrimination on a PI unit is a welcome sight indeed, but not if the discrimination side drops off dramatically at depth. Interesting to see though. About time Fisher.

Cheers Kon.  

I think comparing the AQ Impulse to a GPX is unrealistic. The Impulse is designed as a beach machine with iron disc....It will take an extremely accurate iron discriminator on a beach PI to stop me digging all targets. So many metal detectors in the market have iron discrimination but none to date are totally accurate and as a result those operators who use discrimination above foil will always be leaving small low k gold jewellery in the sand.

Agree Adrian. I should have been a little clearer of my interpretation, as a comparison with a GPX 5000.
This might be the first presentation of a new PI detector, in the form/designed for coin/relic hunting, but there is mention (& no doubt with various cosmetic changes)  using the same or similar PI principle foundation, to soon have a detector designed specifically for the prospecting of gold. Like the GPX 4800 which was specifically designed for coin/relic hunting & although lacking some of the better refinements of the 4500/5000, (maybe not often) but was used & can be used for the detecting of gold. It was more on that line of thought I was basing my comparison of Fishers new upcoming PI gold detector, to the Minelab GPX series, & not on the AQ Impulse alone as it stands) .
Currently, discrimination on all or any current PI unit, is found lacking in some way or another & although Minelab does have a new discriminator patented to work on/with pulse induction systems in the not so distant future, is yet to be incorporated, finalised, as well as judged by the individual detectorist upon its introduction.

Cheers Kon.

I don't place much interest or faith in the discrimination for a gold machine, some want it, I don't care. I try and stay remote with my nugget detecting and have little trash to deal with generally. This new machine is supposed to have accurate iron disc quite deep. The deciding factor in this new machine will be how much will they butcher its performance to get a wide variable ground balance for the nugget detecting version, will it affect nugget depth or sensitivity, the AQ model now has only a 10% variance in depth between all metal and using disc. Not bad.

To me the main secret sauce will be the 7 usec timing, this will give a SDC like detection ability but to far greater depth than a sdc. The nugget version could be a nice lightweight change from using a gpx with heavy coil, I am only good for 3-4 hours with the gpx and a big coil. Then I am looking for something lightweight to swing in the afternoons. This new machine might be it. Dunno yet. At least Fisher is moving forward with something new finally. I credit them for that.

Ditto & I couldn't agree more with you there GBS. Fisher were leaders in their field of metal detecting for gold/coin/relics back in the mid 80's/90's.
The weight factor of the AQ alone, is worth its weight in gold. Its been a long time in the making, but sure am looking forward to what they'v come up with, or what else they might have up their sleeve.

Cheers Kon.

Interesting, the circuit was purpose built with low noise in mind, same with coils, its also a multi channel machine which eliminates detection holes. They are claiming its a very very quiet machine. Here are their latest depth claims by the maker on the beach model:

Hello,

Salt wet sand for US nickel :

IN ALL METAL MODE 17'' without noise at 7µs with a maximum ferrous discrimination

IN TONE MODE 17'' without noise at 7µs with a maximum ferrous discrimination

IN MUTE MODE 17'' without noise at 7µs with a maximum ferrous discrimination

With fast or slow SAT speed setting...

If the competition is better I pay them a tray of strawberries... grinning smiley (with a fast swing without noise)

Alexandre

The first Fisher Impulse beach machine is being shipped to a customer monday 23rd. Production is under way. The Nugget version is in prototype and being tested now as well.

G'day gold bug sniper

I doubt not the coin version in PI will be a killer.
All/any detector/coil combination can be made to run quiet, but to be able to run quiet, over mineralized ground, with minimum loss to sensitivity or depth, is every gold detectorists dream.
Like yourself, I can't wait for the gold version to appear & to see how it stacks up against what we currently have.
Thanks for the update GBS

Cheers Kon.  

Scroll to the bottom of the last page.
Someone has the privilage of testing one out.
With abit of luck we will soon have some real info on this new Fisher PI.

If it was any good why does Fisher not do a promo video?
https://www.findmall.com/read.php?26,2481899,page=4