I recently went out for a few hours detecting not far from my home here in Clermont (Central QLD, Australia). The reason? I had just received a new coil, an 18” Commander Monoloop, and I wanted to give it a go on some deepish ground I knew. Because I had also just bought a new POV (Point of View) camera I decided to rig it up on the detectors stem and record some of the potential action for posterity.
What prompted this blog were my experiences during filming using the large Mono and my thoughts on their effectiveness in the arsenal of serious prospectors. Before we go too far I should also inform you I’m over 6 feet tall and don’t suffer from a lack of strength so swinging an 18” Monoloop is not a big effort for me.
A lot of times it’s felt by the vast majority of detector operators the size of a coil is what gets the power into the ground. I suppose technically this is correct, however what is far more important is the size of the receive area that has to capture the resultant disturbance in magnetic field from a potential target at thousands of times weaker strengths than the transmit field.
It’s the receive where the magic of a large Monoloop takes place in combination with one more important thing of note, namely the size of the coil dictates the amount of windings required for the coil to reach the correct inductance (measurement required for the coil to work). This is why smaller coils have better sensitivity to small nuggets close to the coil (they have more windings) and large coils less windings, due to this fact larger coils are less reactive to ground noise which can be advantageous especially on the deeper gold or gold laying within reactive variable ground.
Knowing this I targeted just such an area with a history of good alluvial gold records. Within minutes I scored a tiny nugget that weighed in at 0.19 grams and shortly after (not shown in video) another piece at 0.15 grams, one of which was in other people’s scratches. Both signals were faint but obvious due to the coil running so quiet. The next signal was also in someone’s unfilled hole and sounded very nice to my ear with a soft and mellow sound that almost always heralds a deep good target (see video for more details).
Where I’ve really noticed the advantages of a larger coil with the GPX 5000 is with the new Enhance and in some cases Fine Gold timings, I feel this is due to a lot of the signal response being removed by the timing in the bid to get rid of the vast majority of ground signal, what is left behind benefits hugely from the larger receive area and quieter running of the bigger coils especially on the deeper bits.
So next time you’re out on a favourite gold spot why not give a larger Mono coil a try, you just might be surprised with what you find! Just remember one thing though, “Low and slow is the Go!”
Jonathan Porter
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Cheers
Jennifer