Which X-TERRA coil is best for me? - Part 3

There are several things to be considered when choosing a coil for your X-TERRA. In Part 1, I mentioned that larger coils detect larger targets deeper, small coils are more sensitive to smaller targets, concentric coils provide a more accurate TID, and Double-D coils separate targets better than comparably sized concentric coils.

In Part 2, I explained how to check your soil conditions to determine if a Double-D coil might be beneficial.

One important piece of functionality we find unique to the X-TERRA is the ability to change the operating frequency of the detector by simply switching to a different frequency coil.

Just as when outlining the attributes of coil size and design, there are a couple generalities to be considered when considering coil frequency. Higher frequencies are designed to maximize their response to targets with lower conductivities, such as gold and iron. Lower frequencies are designed to maximize their response to targets with higher conductivity levels, such as silver and copper.

Don’t get the wrong impression that specific frequencies only detect certain targets. Each of the X-TERRA coils are capable of detecting anything metal. Some coils just do a more proficient job than others, at specific sites.

For example, higher frequency coils are considered the best coil for gold prospecting and jewellery hunting. This is because, on the X-TERRAs, high frequency coils expand the target ID range for low conductivity targets and compress that target ID range on targets with high conductivity levels.

Conversely, the low frequency coil expands the target ID range on high conductive targets and compresses that range on targets with low conductivity levels.

If you’ve read my eBook, Understanding your X-TERRA, you know that I prefer using the 3-kHz coil in and around old homesteads because it provides a very distinct audio response on deeply buried iron. If you've ever hunted an old homestead, you know how much iron can be buried in the ground!

With the high frequency coils, and to a certain degree the medium frequency coils, the audio response on deeply buried iron does not provide the harmonic audio distinction that I get with my 3-kHz coil. The response from this coil greatly reduces the “wrap around” effect often encountered when trying to separate deeply buried iron from an old coin.

This example not only takes into account the low frequency providing good information on high conductive targets, but also demonstrates how we can use this technology to assist us in identifying targets whose conductive properties are not “favored” by a certain frequency. This can best be depicted by comparing the width of each notch segment when using each of the three different coil frequencies.

In Part 4, I’ll offer some practical advice for making a coil choice. And, finalize this discussion on X-TERRA coils.

Randy Horton (Digger)
You'll never know for sure... unless you dig it!