Thursday, July 14, 2005

Gain Experiments at the Beach - CharlesNY

I have not been able to get to the beach with my Explorer this year but some have and are getting good results. I recently got permission to share with you some beach experiments made by CharlesNY on Gain and Sensitivity. They are not yet conclusive but do contain great insight. I will update it as Charles gets more results or I try them myself.

From CharlesNY -

A friend and I have been hip deep in building ourselves a better beach coil for the Explorer. One of the goals is to reduce or eliminate the falsing that takes place in the wet sand on our NE salt water beaches. Coils which seem perfectly stable in the dry sand false when you move out onto the wet sand or into the water. All the coils we have tried seem to false, stock coil, ML 8, and the other brands. The degree to which they false varies quite a bit, and even with a group of stock 10.5 ML coils some are more prone to falsing than others.

I noticed something when we were testing an 11x14 eliptical recently that got me thinking about sensitivity verses gain.

My friend had his sensitivity turned way down to reduce the falsing, something in the 16-18 range which I hear is common for beach hunters. But he had his gain higher, 8-10 so that he would not miss the small gold.

I was setup just the opposite with my sensitivity at 26 and my gain at 5. Here's my reasoning for this...if you rated a target on a scale of signal strength from 1 to 10 a coin or ring might be a 10 compared to a wet sand false which is more like a 5. But when you increase your gain it boosts the wet sand false higher in volume to the point that it sounds about as strong as a coin or ring and so it was difficult for me to tell the difference between a wet sand false and a real target.

But I thought what if I reduced my gain to 5 (I normally run it at 7), that might quiet down the wet sand falsing to the point that I could ignore them and just concentrate on the loud stronger signals. That approach worked out pretty well as it turned out. I was still digging deep and sometimes quite small targets.

Now here's the interesting part of this story. I had a decent signal on a deep target and asked my friend to come over and check it before I dug it. He could not hear it at all, yet it was pretty decent on my machine. It was a bit fainter than a solid signal which makes sense with my gain at 5 but it was clearly there. With this gain at 8 or higher why couldn't he hear it???

Here's the question...which is processed first by the Explorer electronics, the gain or the sensitivity?

Keep in mind that the Explorer transmits at 100% power no matter how you have your machine set up. When you change your sens or gain its just modifying that signal its not varying the amount of transmitted signal strength or received signal strength. Its saying here's a signal in my electronic brain, and based on your settings it processes the signal and provides you with a response.

Now...does it make sense that it would process the gain boost first before the sensitivity setting? I think not. It makes more sense to process the sensitivity setting first, eliminating the unwanted noise and ultra faint signals and then apply the gain boost in volume to those that are left.

This would explain why he could not hear my target, with this sensitivity turned way down to 16 I think it eliminated this target where as my machine at 26 allowed it in. Therefore a higher gain cannot boost a signal that has been eliminated already by a lower sensitivity setting.

This is just a theory, but I think a lower sensitivity even on the beach is not a good thing which has been my experience in land hunting deep targets. Something to think about.


In summary, it appears that CharlesNY is experiencing more depth and less falsing by reducing GAIN first before SENS. Cant wait to try it.

HH, Bing