Technical information desired

Question in relations to the F75 coils.
I would like to have an illustration of the signal pattern transmitted from both the standard 11" DD and the 5" DD coil.

From what I've read the concentric coil has a so called cone shaped pattern but what about the F75's coils?

Youre already half way there.

The DD coil has a "hot strip" down the center, front to back. Imagine a broom as it sweeps along the ground and that is the idea.

The DD coils usually pinpoint of the ends, as well.

Laymans terms just turn on the windshile wipers of your car and will get the basics. Have seen and read various ways to pinpoint but working with either edge usually works well...Just an addendum to dahut who was right on with his post...

Amp info:

A true 'elliptical' DD coil will present a narrower/tighter EM footprint.....as compared to a concentric (round) DD coil. The round DD coil will have a footprint that is a bit wider.

dahut Wrote:
-------------------------------------------------------
>> The DD coils usually pinpoint of the ends, as
> well.

Would you elaborate on pinpointing with the DD coil? I've been having trouble zeroing in while using the stock 6x11 DD that came with my F75 LTD.

Thanks

Ill speak about this in general terms, considering a shallow target like a coin:

When you get a response from the detector indicating a target hit, it is telling you the target is somewhere under the center of the coil. The "hot zone" of detection on widescan, DD coils is in a strip down the center, from front to back.

So you wiggle the coil back and forth and draw the coil rearward until the signal stops. This will place the target just at the tip of the coil.
This works either at the front or the rear, but most people visualize the process best at the front tip of the coil. Since you cant see the target, you have to keep the coil moving and coordinate the beeping with smooth, small backward sweeps of the coil.

The deeper the target is, the more it will pinpoint towards the coils center. This is because the targets field tapers toward the bottom.

The best thing to do is to lay out some visible targets on clean ground and work at this until you get the hang of it. Remember, don't "hover" the coil. Keep it moving in smooth motion.

The entire 'beam' under the DD coil ... is the 'hot spot'. BUT......the hottest spot (from fore to aft) in this entire beam...... is the dead center of the coil.

dahut Wrote:
-------------------------------------------------------
> Ill speak about this in general terms, considering
> a shallow target like a coin:
>
> When you get a response from the detector
> indicating a target hit, it is telling you the
> target is somewhere under the center of the coil.
> The "hot zone" of detection on widescan, DD coils
> is in a strip down the center, from front to
> back.
>
> So you wiggle the coil back and forth and draw the
> coil rearward until the signal stops. This will
> place the target just at the tip of the coil.
> This works either at the front or the rear, but
> most people visualize the process best at the
> front tip of the coil. Since you cant see the
> target, you have to keep the coil moving and
> coordinate the beeping with smooth, small backward
> sweeps of the coil.
>
> The deeper the target is, the more it will
> pinpoint towards the coils center. This is because
> the targets field tapers toward the bottom.
>
> The best thing to do is to lay out some visible
> targets on clean ground and work at this until you
> get the hang of it. Remember, don't "hover" the
> coil. Keep it moving in smooth motion.

Thanks dahut. All metal pinpoint (trigger pull), takes a bit of time and for some reason I'm often off the mark when I dig. Your posts in this thread got me to thinking. Maybe in fairly trashy areas the coil is seeing some response from nearby trash as well as the primary target. Also any "ground" response makes all metal pinpoint more difficult. Pinpointing in discriminate mode as you suggest might be more accurate in these situations. I'll sure give it a try. What's your opinion on the scenario I brought up?



Edited 1 time(s). Last edit at 04/07/2010 03:32AM by dgc.

Im not certain which scenario you are referring to.

As for pinpointing in DISC, it will always be smoother and quicker than switching modes and hovering around over the target trying to home in. Keep in mind as you work at this that the hump running the length of the coil center is the active response zone.

It helps if you pictures two "D's" laid back to back, each belly of these "D's" facing opposite and to either side of the coil. The straight backs of these "D's" meet and overlap in the center of the coil, in the active response zone about 1-2" wide. The name we use for such coils, "DD," is misleading, as it does not accurately describe the windings within the coil.

Detectors with fast response, like the Fishers, are especially good at DISC pinpointing. But you are right, if there is more than one target within the coils field at the same time, it will cause obvious problems with pinpointing. Sometimes turning the coil in a different direction will alleviate this - 90 degrees away there may not be anything else to get in the way.

This is the other reason why smaller "sniper" coils are often suggested for use in congested (trashy) sites. They simply "see" less of the matrix and so are not as affected by multiple targets when it comes time to pinpoint.

In trashy sites, , , it is recommended to NOT use the PP feature....especially if any form of Disc is being utilized........due to multiple targets being under the coil...'pulling' the coil away from where you will need to dig. Use the regular detecting mode....and do your best.

NASA-Tom Wrote:
-------------------------------------------------------
> In trashy sites, , , it is recommended to NOT use
> the PP feature....especially if any form of Disc
> is being utilized........due to multiple targets
> being under the coil...'pulling' the coil away
> from where you will need to dig. Use the regular
> detecting mode....and do your best.


Thanks Tom. I believe that is precisely what has been happening to me.

Sometimes I pinpoint if I've got a 2 way response and not a 4 way to try and determine if the coil is just falsing on nearby iron. Usually in this case the pinpoint location doesn't agree with the sweetest discriminate tone location

VERY common; hence, use the best 'ID mode location'.