The Nautilus DMC-II B
By Gary's Detecting
" How did this metal detector slip through the net ?"
The Nautilus DMC 2B
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Nautilus review and basic information by Garys metal detecting
Most of us have heard of the Nautilus name but like myself how many of us know about the Nautilus, by this I mean have we ever stopped and read about this machine or talked to people who own them.
For quite some time I have been talking detectors with my good friend Richard from Scotland, some of you may know him as Filterozzle on the forums, Richard is a smart methodical guy who just loves quirkiness and just thrives on fitting square pegs into round holes...will he be beaten ?....no never, even at the age of 6# I have just been informed he is still trying to master the Rubik's cube.
Most conversations we have had in the past tended to drift towards the Nautilus,
he has always been an avid fan and owns several models, personally they have
never excited me although based on Richards enthusiasm I have always wanted to
test one. I finally noticed one for sale.
I decided to buy it out of curiosity, the machine arrived a couple of days before Richard was due to visit me, so I had some time to get to grips with this odd looking machine.
It was a fine example of what not to have on a modern detector, 4 x 9 volt batteries clinging to the underside for dear life, a metal control box with some lovely gaps in it to allow water or dirt to enter, potentiometers that looked like they came out of a "lost in space" stage prop and to top it all a concentric coil...who uses concentrics these days ?
I had already had a lot of information from Richard and my shorthand telephone notes were scribbled onto a piece of paper, the writing got smaller and smaller as I was running out of room, until it started going up the page rather than across, which is quite normal these days.
My first test was in the garden, first you have to balance the coil to the machine...not ground balancing this is totally different, this is to tune the coil to the machine, and should also be done throughout the day, especially if the temperature changes. It's an easy process and takes less than a minute. The Nautillus has lots of tweak able features but the key ones are coil voltage from 6 to 44 volts, sensitivity and discrimination, I will cover these features later in this article.
The garden test went well and I soon became familiar with this machines language, the best way I can explain is : The Nautilus is two machines running on the same coil, you have an all metal machine and a discriminating machine, the all metal and discrimination circuits are split between your two ears...one channel in each, which sounds bonkers but really is very clever. As you approach a target the all metal starts to kick in (left ear) with a low tone then as you pass the target you get a high tone in your right ear if its non ferrous or just the low tone left ear if it's non ferrous, well that's the theory.
large mis shaped iron fools most machines, with the Nautilus you get a different signature, left ear then as the coil is leaving the target a right ear sound, the clue is in the signal timing, a good signal will have the all metal and discrim both at the same time as the target passes over the center of the coil with no signal lag, it sounds tricky but in reality it's quite simple...providing you have two good ears !
When Richard arrived we had a catch up and headed off to a local field, I had mentioned to him that I was strangely comfortable with the Nautilus DMC-IIB and found it extremely sensitive to small targets, his smug look said a thousand words.
Out in the field this machine excelled, on some targets it really showed up some top of the range machines we took with us...the Dinosaur was eating the robots !, my finds pouch was full of non ferrous and to be honest I wasn't really that good with it, but it just felt right.
The following week I had a club dig and decided to use the Dinosaur, as we were getting ready the lads had a good laugh, "what the F###k have you got there Gaz" "did you find it at a car boot ", " did you take the batteries out of your smoke alarms " and so on, which made me feel very much like the under dog, personally I have always backed the under dog which is probably why I am so poor.
The dig got underway and I had to spend a little time getting the settings sorted as the soil was very sandy and iron contaminated, but very soon I started finding, there was a copse of trees that most of the lads were working around, so I made my way over, as I approached I got a small signal, Graham and John were near by so I asked them to check it....John "rubbish mate", Graham "uncle Brian" his name for iron, I knew it wasn't but said to them they were probably right and asked them to hang around while I dug a very small button...I felt king of the field.
By lunch time the mocking had turned into "So Gaz where can I get one" "will you be selling these", "how much are they"...Oh how the mighty have fallen !
Sadly Stephen Garriss, President and major owner of Nautilus Metal Detectors recently passed away so I am guessing the Nautilus is no more unless someone releases the schematics to another company, which is worrying if I ever need a repair or service, hopefully Pentechnic www.pentechnic.co.uk can throw a lifeline as they are the UK's leading metal detector repair centre.
For some people this machine will have no appeal whatsoever and I can understand that, it is very different to the conventional models of today and you do have to work with it. For me the Nautilus is a keeper I feel so comfortable using it, another working tool to the collection.
The Concentric coil worked in harmony with the machines circuit, I would have never believed it, the balance is perfect, I have to say the Nautilus is one of the smoothest most responsive machines I have ever used....If your up there watching Mr Garriss I salute you, your Nautilus is a true work of art how did I ever let this one slip through the net !!!!!
If anyone has a Nautilus or spares they want to sell please contact me on email@example.com
Due to the audio nature of the Nautilus conventional headphones may not work, you may need specialist units that are wired differently, please drop me a line if you require more info.
Operating Frequency: 14kHz
Audio 1: All Metal and Non-Motion Discriminate 240HZ tone
Audio 2: Ground Reject Discrimination 950HZ beep
Search coil type: Concentric
Search coil size: 10
Aluminium control box dimensions, approximately: 177mm x 128mm x 77mm
Weight of stems and control box, excluding batteries, approximately: 1250g
Weight of 10 coil, including stainless steel coil bolt, approximately: 460g
Batteries (not supplied) 4 x 9v PP3, alkaline or NiMH rechargeable's
Battery life approximately 20 hours
Maximum stem length, 126cm
Minimum stem length, 106cm
Headphones: stereo/mono, 32 ohms, twin volume controls
A very brief description of the Nautilus controls
Lower control box
SLB R and C. These knobs are used to balance the coil in conjunction with the SLB switch.
Auto-Tune on/off. Turns the detectors auto-tune function on or off,
operates in the All Metal and Non-Motion Discrimination modes.
Transmit power and sensitivity
Treat these settings with respect, it is counter productive to ever power the machine if site conditions will not allow.
The battery mounting
At first it is quite laughable, I now like the fact it is different, powerex rechargeable batteries and charger were a fantastic investment at £60
The ground balance has a very fine operation, when you make other adjustments especially the transmit power, you may have to re ground balance
This control effects both the All Metal and Motion Disc modes, pay attention to the ground balance level, if you get it wrong you will reject large Silver, I always take a test piece with me to check.
The factory pre sets are a very good starting point when learning this machine.
Upper control box
SLB (Search Loop Balance) on/off. Switches on and off the detectors SLB
On/Off. Turn the detector on and off
The re tune button
Red re-tune button. Located on top of the hand-grip. Depressing the
button restores the threshold when working without automatic tuning.
The discrimination on the Nautilus is so sharp and precise I can now see why they have chosen this type of potentiometer, it is second to none.
DMC IIB main controls
Transmit Power Regulates the power and overall gain of the detector.
Ground Balance Balances the detector to the level of mineralisation in
the soil. .
Discrimination Sets the level of discrimination the operator desires.
Sensitivity (Discriminate left bank) Controls the sensitivity of the
Sensitivity (All Metal right bank) Controls the sensitivity of the All Metal mode.
Threshold Sets the level of audio threshold.
There is another model available which is slightly easier to set up it is the Nautilus DMC II BA,
it has an auto coil balance and fixed all metal and discrim sensitivity.
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