Is The Bigfoot Coil A DD Or A Concentric?

[Woodbutcher]

I was trying to figure it out, hell I have no clue.. when I use it on the V3i I can run the RX to 15 and sensitivity to 90 with no problem, really quite .. But the nickels ID in the 50s, at least in 3 frequency…I put it on my M6 tho and it rocks, ID for a nickel is 18-20 and all other coins ID correctly too…thing just kills mid conductors at depth on the M6,,But is it a DD or concentric,the Bigfoot coil? I’m in western Pennsylvania, not mild but not real mineralized either, just old coal ashes occasionally..Seems to get the depth of a DD here,,concentric coils usually don’t do as well it seems in my area for depth.

[Steve Herschbach]

Neither. It’s a figure 8 winding, which means polarity reversed front to rear. See pages 4-5 here. The DFX was specially made with the Bigfoot in mind and compensates for this, MXT does not. I still have a DFX with Bigfoot combo.

 

[Woodbutcher]

Thanks Steve for the reply, I don’t have a DFX but I might hafto look into getting one. I’ve had a few over the years but never clicked with the r2d2 tones

[Steve Herschbach]

20 hours ago, Woodbutcher said:

Thanks Steve for the reply, I don’t have a DFX but I might hafto look into getting one. I’ve had a few over the years but never clicked with the r2d2 tones

I just noticed all the reference links I put on that old thread are to sites that are gone now, need to see what I can do to fix that.

See pages 4-5 here for info on figure 8 winding

In many ways the MXT is a better detector than the DFX. Ironically I like the DFX precisely because it is very mild mannered unlike todays overly twitchy detectors, and my setup is still the best park and field ring scanner I have used in 50 years of detecting. Really need to get back on that. 

The coil does also work on the MXT but it's a bit odd. It took some digging but here are the original operating instructions that came with the coil. The same version worked on MXT and DFX, literally the same coil. The instructions are not the best as they kind of stuck the MXT part in italics in the middle of the DFX stuff, but it does give very important info about the coil you need to know to run it properly. The ground balance info at the end is critical.

JIMMY SIERRA BIGFOOT OPERATING INSTRUCTIONS DFX/MXT

This NEW Bigfoot coil is a completely new concept, designed especially for the DFX. It is not shaped differently JUST to LOOK high tech. IT IS HIGH TECH! This particular shape is necessary to house a coil design known as differential geometry. This design has two goals. First to cancel the effect of much of the ground mineralization before it gets to the detector and secondly to cover a large area of ground in one sweep from tip to tip for the full 18 inches of the coil length, much like a windshield wiper. An added bonus is that it helps to reduce 60 cycle interference, such as transformers and power lines. The BIGFOOT is 18 inches long and 3 1/2 inches wide. 

The DFX Bigfoot will work on the New MXT, but in a unique fashion. The Bigfoot on the MXT will produce a single beep on the front half of the coil and either a double or a wide beep on the rear half of the coil when passing over a target. In addition, it may read about 2 numbers higher on certain targets, which can skew the Icons (eg quarter to read half-dollar). The front half of the loop should be used when trying to identify targets on the MXT, as it is more dependable. Even though the MXT tracks the ground automatically while searching, do not forget to ground balance initially by pump-the the coil up and down a couple of times with the tip of the coil on the ground at a 45 degree angle as noted in the last paragraph below, with Track toggle set to GND. After that you can either leave tracking ON or set toggle to LOCK. I prefer to lock tracking off except in heavy mineralization. 

While the detector is operating in the GEB DISC (motion mode) the BIGFOOT detecting targets across the entire 18 inches of coil. When the detector is operating in the GEB all metal (non-motion) mode, the BIGFOOT is detecting targets ONLY on the front half (9 inches) of the searchcoil. Unlike the Spectrum & XLT, the DFX does NOT require the use of "Absolute Value" as the DFX only detects on the front half in the all metal mode, such as when in the Prospecting Mode. 

Pinpointing with the BIGFOOT is very simple and accurate. Squeezing the pinpoint trigger on the detector will make the BIGFOOT go blank (negative) on the back half (9 inches) of the coil. The front half of the BIGFOOT remains sensitive (positive). In other words, the target will only be heard under the front half of the coil. The trick, then, is to center the target by moving the coil from side to side till is seems to be midway from either edge and then squeeze the pinpoint trigger and push the coil forward like on a shuffleboard. The target will disappear as it leaves the midsection of the coil (marked by the two arrows) Thus by pushing the coil forward and backward you can easily hear the sound of the target appear (when it is under the front part of the coil) and disappear (when it is under the rear half of the coil) That point where it appears and disappears is exactly at the center of the coil between the arrows. The rear half of the coil is actually rejecting the target and so you hear a very distinct sound when the coil is pushed forward and the front half leaves the target. You might note that the coil is first moved side to side to center the target between the side edges of the coil, much like with a round coil and after it is centered, squeeze the trigger and posh the coil forward. Of course, if no target is heard when the pinpoint trigger is squeezed, the target is probably under the back half of the coil and being rejected. You should then just pull the coil backward a bit to get the target under the front half where it will be detected and then push and pull as described. Some users prefer to pinpoint right off of the front of the coil. This is OK, but I prefer to use the above method as it is more precise and very fast and easy once you get used to it 

IMPORTANT: You may AIR BALANCE the BIGFOOT the same as any coil, with the Bigfoot held in the air....HOWEVER, you MUST GROUND BALANCE the detector with the BIGFOOT pointed at the ground at about a 45 degree angle , with the FRONT tip of the coil touching or just above the ground and the REAR of the coil held OFF the ground at 45 degrees, You will then lower the coil parallel to the ground for searching as with a standard coil. It is, of course, best to keep the front and rear halves of the coil as close to parallel to the ground as possible. Use shorter strokes in trashy areas and broader strokes for covering larger, cleaner areas. If at any time, the Bigfoot appears to loosen up on the rod and wants to tip or paddle, it is time to either clean or replace the rubber washers where the rod joins the coil. The nut should only be tightened "finger tight". 
 

[Woodbutcher]

Thanks Steve, very interesting info. Here’s a pic of mine, I resealed it where the two parts go together on the coil, and put bed liner spray paint on the bottom of the coil. I looked for a coil cover and I don’t think they made one..But these coils can’t be bought anymore new so I figured I better reseal it and paint-the bottom of the coil for reinforcement.. Only takes a small crack to let moisture in and the forget it, coils shot..