DFX limits

[TXDIRTFISHER]

How do you know when you've gone beyond the limits on the DFX (AC, preamp gain). I set up a backyard test with several coins buried at 7 inches. Some are flat, upright, and slanted. The coins are .50, .25. 10, and a penny. The preset coin program doesn't do well on the flat coins and won't even detect the ones on edge. Deep silver program does a little better but it isn't impressive. When I enable single freq 3khz things get a lot better.

I took the Deep silver program and tweaked it a bit (turned up AC and preamp gain). After I did a GB (my yard has almost no mineralization) the detector went nuts. I was getting signals when the coil was in the air (no electrical lines around).

What are the indications that you've got the DFX set too "hot"? I'm trying to make my DFX detect the coins in the yard at 7 inches, plus make it detect the ones on edge. So far 3khz works the best. I need some help on how to set this up or how to recognize when I've turned things up too much. Thanks.

[Admiral de Salee]

Assuming Gain is at 3, I think a common error (it was mine, anyway, as recently as the start of the 2007 season) is to have AC too high for local EMI conditions.

Knowledgeable people like JerDFX run AC at 85, "because they can".

I was running at about 75 in my old 'standard custom program', but I've dropped that to 73--which seems to work okay as a starting point when I'm near fat power lines. I still might get a bit of noise when I raise the coil a foot, but I can pretty much believe what I hear on the deck.

There's a standard routine for alternately adjusting Gain and AC Sens to run as hot as you can at your site. I think it's in DDwtDFX (Jeff's book), which is presently in the basement, sad to say.

[DFX-SE Gregg]

Very simple, to check if you are running to hot especially your ac sens. air balance at waist...when you go down to ground and ground balance...you should be able to lift detector coil up toward waist and back down to ground with the detector remaining quiet...if you are getting all kinds of signals...sounds lower your ac sens...and try air/ground balance again,,,good luck!

[Kas]

There is a section about this in Jeff Foster's Digging Deeper with the DFX. www.fielddepth.com

In short he says

Start
Set pre-amp gain to 4 pull and release trigger to exit out of menu
next
Is the DFx stable with the coil held steady at waist height?

If yes increase Ac sens by 4

If no
decrease AC sens by one.

It a big circle of questions and reduction of AC sens until stable.

No this.
Best to decrease AC sen than pre-amp gain until you get under 70 on the AC sens.

I usually run mine

pre-amp 3
ac sens 75 I can't get much more than that around my area. Depends on EMI and ground. About the deepest I can detect is 7".