The kHz Ratings on a Metal Detector

kHz -  kilohertz

Have you ever wondered when looking at the specs of a metal detector what the kHz means. To be honest  when I first started metal detecting I thought the higher the kHz the more powerful the machine was. I was so wrong. Over time I have got to understand more about the kHz of a machine. In this post I have tried to put together a basic explanation about the kHz rating of a machine and how the different ratings do different things. If you are not sure about what these ratings mean then it could help you to decide on a first machine or an upgrade.

So what does the kHz mean.  Now I had to copy this from my notes as my tiny peabrain wouldn't hold it. The kHz rating of a metal detector stands for the number of times by 1,000 that a sine wave current is sent and  then received per second by the coil. So, 3kHz stands for 3,000 times per second and 18kHz stands for 18,000 times per second. There is quite a bit of difference between the two and it affects the way in which a machine 'sees' a target. There's quite a bit of scientific stuff going on here but I will keep it basic so you can understand, as I had to. If it has stirred your juices for the scientific aspects there must be lots of info around the net.

Most of us in the UK don't do any gold hunting, I mean like our American cousins who head up into the mountains to search for gold deposits. So here we mostly operate machines in the 3kHz to 19kHz range. Metal detectors with a higher rating like 20kHz to 30kHz are mainly used for nugget hunting.

How do these kHz ratings affect a detector, lets take the 3kHz to 6kHz range first.
Machines in this range are better at distinguishing ferrous metals (rusty old iron and nails etc). Also this range is not affected so much by ground mineralisation. The larger and thicker coins will be found at greater depths than higher rated kHz detectors. Discrimination is also good in this range. Quite good on the wet sand.
 The minus side of this range is that the recovery speed is slow and don't do to well in finding thin coins like small hammered silver.

Now take the 16kHz to 19kHz range. These detectors can have very fast recovery speeds and are great at recovering the small and thin coins including gold, even in amongst the nails.
The minus side, depth on the larger thicker coins will be less than the lower khz machines and iron can be a problem on normal discrimination unless it has tone ID. Ground mineralisation can also be a problem also making it not very good for the wet sand.

The 8kHz to 15kHz falls in between the two. This range is neither the deepest or the fastest but are not affected by some of the problems of the other two. According to statistics, this range has accounted for most of the finds made to date in our hobby. Discrimination is good in this range. Not too bad on wet sand if the discrimination and sensitivity controls are used well.

I hope this post has given you some idea now on the kHz ratings of a metal detector or stirred you into finding out more. At least you can see at a glance how the kHz rating can affect your choice of machine.
Remember, there is no 'Best Detector', only what's best for your sites and needs.