The Deeptech Onyx 'River Performance'

I wanted to get the Deeptech Onyx for my river hunting, did I really need to get another machine? no not really but I genuinely love metal detectors, I can't have too many, it's the simplicity within the operation of the Onyx that attracted me to it. It's very similar to the Vista X just without the extra settings and options, I've used the "X" on the river with great success so I knew that the Onyx would perform really well. Deeptech were kind enough to build me a 5.5' inch coil because I don't require the larger stock coil for my hunting on the foreshore.

The build quality is along the same lines as the Vista X, it's the same shaft, module and battery compartment, the overall design isn't the best but to be really honest it doesn't bother me. I'm far more interested in the way a machine performs as opposed to what it looks like. The controls are simple, you have threshold, discrimination, volume and a switch that changes between disc mode, all metal and ground balance. Ground balancing the machine is easy, you find an area of ground that contains no metal, you push the switch down to GND and slowly raise and lower the coil. When the audio evens out or goes silent then the machine is ready to go. This might have to be checked and repeated if the ground you're hunting over changes. 

I'm not looking for depth when I'm hunting the river, it's all about separation and unmasking the shallow targets in, under and next to the iron. In this environment I tune all my machines down. Personally I find Deeptech machines to run with a high gain and the preset sensitivity on the Onyx provides more than enough depth even when the threshold is set to zero. Due to the overall sensitivity I swing the coil about 3 inches off the ground and this still provides more than enough depth.

There are a few basic rules that I follow to get the most out of it on the terrain I'm hunting, the first is swing speed. the Onyx has a really fast recovery speed so I swing slow, this allows the machine to separate targets perfectly and lock on to the really small stuff, swing too fast and you'll miss the smaller targets because you can mistake them as false signals. If you're going to swing really fast in the iron then you're going to be missing stuff as well, a slow to moderate swing speed is perfect. The second element to understand is the discrimination level, if you push the disc up you're going to kill the machines ability to unmask effectively. I set my disc just under the red preset level, keeping it here aids unmasking, it actually does a fantastic job but you have to listen very carefully and understand what a potential masked target sounds/feels like.

One important point that needs to be mentioned when you're hunting with a low discrimination setting, you're going to be letting a lot in, your hunt is going to be lively so you need to know how to identify iron. Also you have to take into account that the machine is operating at 18KHZ so it has the ability to pick up the smallest of non-ferrous signals. On the river there's hundreds of tiny non-ferrous fragments littered all over the surface so it can give the impression that the machine is unstable, this isn't the case, it's just really hot on the tiny targets.

The tone of the Onyx has lots of nuance and even with the disc turned all the way down it provides enough audible information to I.D iron. You have to remember that the environment I'm hunting takes iron content to an extreme so I need to have the least disc I can get away with to enable me to hear the masked targets. If I was using the Onyx in the fields where iron isn't so crazy I would leave the disc setting at zero, having the disc this low still provides you with enough clues that you've got iron under the coil, you just have to go slow and analyse all targets carefully.

Identifying iron with a low disc is exactly the same as all my other analog machines, to I.D large flat iron I'll draw the size of it and listen for the signal to break up on the outer edges. Raising the coil up high also helps you to suss out the larger pieces of iron because you get a strong signal when the coil is a considerable distance from the ground. Large and lumpy iron gives an overload signal and clicks on the perimeter, after using the machine for a while and applying your mind it becomes very obvious what it's telling you.

To sum up the Deeptech Onyx is a wicked little machine for the money and on the river foreshore it performs great, I have no doubt it will perform equally as well out in the fields. If you're going to be setting it up and swinging it like a Deus then you're going to be left disappointed, this detector isn't going to serve you. As with all analog machines, if it's set up right and you swing with a considered approach carefully listening to what the machine is telling you then you will mesh with the detector just fine, anyone with a mass-produced, digital frame of mind won't get on with this machine. 

The Onyx With Its Stock Coil