I just took the V3i outside and turned it on and no falsing with the coil in the air. Turned Rx gain up to 15 and no overload. But if you barely and I mean barely touch the coil if falses every time you touch it.
I understand your frustration. However, give me a minute to cover a few things about the Vision regarding falsing. I currently own seven detectors and have many hours swinging a V...my original was serial #16.
The fact that you get no overload with Rx at 15 in the air tells
me that the detector and the 10D2 coil are fine.
Unlike other detectors which need to be cranked up beyond the factory settings to get good depth, the Vision comes hot right outta the box. I'm an old MXT'er. That machine is good with the factory presets. However, to get the most out of it one needs to run it on the edge of insanity...as close to maximum gain as possible.
When I got my first Vision, I naturally assumed that the answer to everything was to run the Rx Gain on 15 to get the depth that the machine was touted to have. Wrong.
Without getting into filter settings, let me pass along the best advice I ever got when first using the Vision...
1. Start with the Rx Gain around 7 and the Disc Sensitivity around 78...then perform a ground balance. Once you've done this, you are ready to adjust BOTH the Disc Sens and the Rx Gain to obtain optimum settings for the ground under the coil.
2. Unlike most detectors (DFX excepted), there is not a single control (usually labeled Sensitivity) that adjusts both the returned signal that enters the box (Rx gain) and the algorithm in the firmware that decodes the returned signal (Disc Sens). A Vision works best (no falsing, but deep) when the user has balanced the two variables. I've found over time the more important one is Disc Sens.
3. Start adjusting both upwards until the machine falses when you bump the coil. Once it begins falsing because it's just too powerful for your ground conditions, it's time to start backing the two controls downward. Here's the rule-of-thumb:
Sacrifice Rx Gain for Disc Sensitivity.
I realize (cause I've been there) that many first time users think Rx has to be at 15 to get the results that you've read about. Not true. A Vision that has been stabilized with good ground balance and an Rx gain of 5 will be incredibly deep when it's stabilized by an appropriate Disc Sens setting.
I'll be glad to discuss it with you further if you're interested. Drop me a PM and we'll talk.