Tracking Speed, Motion & Sweep Speeds – PART 2

Coil Sweep Speeds

One of the hardest skills for a new detector operator to develop is a slow swing speed. I’ve lost count of the number of times I’ve seen new users swinging the coil so high and so fast you’d swear they were using a whipper snipper! The gospel of “low and slow” has been preached enough, but the importance of a slow swing speed has never been greater since the introduction of the slower Motion options in the GPX series.

Basically, for maximum stability and to detect targets at the limit of their detection range, a slower sweep speed is best, but what is slow? I have done a number of tests to determine what a slow sweep speed actually is, and on average I would say that it should take you 4 seconds for every left – right sweep. Now, there are several variables to this, which can determine what the optimum sweep speed is:

1. Mono coils can allow a slightly faster sweep speed.

2. If you sweep too slow, a large deep target can sound quite broad, and    almost ground noise like, particularly with a large mono coil.

In this instance a slightly faster sweep speed will sharpen the target response, but too fast and you may miss it altogether. If you sweep too slow you won't cover much ground, and as mentioned deep targets may be difficult to recognize.

So, the next question is - What about when I am patch finding?? Obviously there needs to be a compromise between detecting slow for maximum sensitivity and detecting slightly faster to cover the ground. I guess if you think you are in a good looking area (whether you know there is gold there or not) you should slow your sweep speed down a notch. On the other hand, if detecting in a large open area, with good looking gravels, ironbark trees or other good indicators but no natural or obvious concentrations (i.e. the gold could be anywhere) then opt for a slightly faster sweep. The trick here is to go fast enough to cover the ground, but not too fast so as to potentially miss a 1 gram nugget buried at 6 inches, that is on the edge of a 40oz patch! A good combination here would be a Mono Coil, Medium Motion, Slow Track, and drop your Rx Gain slightly to keep the threshold nice and stable.

For patch finding and general detecting, about 2 seconds for every Left-Right swing is a good compromise, particularly if using a Mono coil. So what about working a small defined area that has produced gold? I’d say that approximately 5 seconds for every L-R sweep is recommended, and yes that means 10 secs for one full return sweep, from left to right to left. I have seen video footage of operators in WA detecting at a rate of 3 sweeps in 2 secs, and although they do find gold, I'd be very keen to walk behind them and follow their chain lines!!!!  

Nenad Lonic