I've tried to buy more bigfoot coils (I have one on my XLT, and a second one on my wife's IDX) because both of mine a getting pretty beat up after about ten years of nearly daily use. No luck. The problem, as I understand it, is that the bigfoot coil cannot, with current technology, be mass produced. They still have to be hand wound (I don't know why, but this what I've been told) and the "hand-made" cost is simply too high.
I really don't understand this, because really the bigfoot is just a double D coil front-to-back instead of side-to-side. If you look inside one (I have because I've had to repair mine a couple of times) you'll find essentially three loops - like a squared figure 8 inside a squared zero. The loops are wound around styrofoam shapes to hold their shape.
I'm not sure about this but, it appears to me that the "8'" is the transmit coil arranged like a double D except front to back instead of side to side, and both halves must be exactly the same reactance so that the signal induced into the receive coil by one half is exactly the same strength, but opposite, the signal produced by the other half. This is accomplished by winding one end of the "8" in one direction (clockwise) while the other half is the opposite (counter-clockwise). The number of turns and the geometry of the loops have to be identical also. The "zero" loop is the receive coil. The signals induced into the receive coil by the two halves of the transmit coil, being equal but opposite cancel each other out and no signal is seen by the detector. When a metal target comes under the coil either end of the coil, that careful balance is upset, and a signal is produced. Interestingly, if the target is EXACTLY centered on the coil the two coils are once again "balanced". That is why one way to pinpoint a target with the bigfoot (this is not the method I use) is to find that point which produces NO SIGNAL (a very sharp signal cutoff) or "null" indicating the target is centered under the middle of the length of the coil.
Mechanically, the bigfoot coil has a couple of problems. First, the upper and lower halves of the cover are plastic seam welded together using methyl-ethyl-ketone. This produces a pretty, but no so durable, fusion. Many coils have developed cracks in this seam weld allowing moisture to get into the coil. There are pieces of foam rubber surrounding the coils to protect them from being distorted by a small bump, and this rubber soaks up the moisture like a ....well, it IS a sponge. The result is a coil that cannot ground balance, screams at everything; in short, doesn't work. Opening up the coil (VERY carefully), drying it out, and putting it back together is a time-consuming but not too difficult task. When you have to coil opened, though, you must be extremely careful not to damage or alter the coil windings, or the farady shield (pieces of aluminum foil connected to wires taped to the top and bottom covers).
The second problem is that the "ears" where your lower shaft attaches to the coil are not really strong enough. I have seen more than one broken off by accidentally bumping the coil or hanging it on something while swinging from side to side. If this happens to the coil near the front or the back, the coil twists and the "ears" could be history. My wife had this happen to her (she didn't even know how- or when - she did it) but fortunately for me a gentleman who knows one heck of a lot more about these coils than I ever will lives only a half hour drive away and he was able to make a repair.
Anyway, getting back to your question, I have asked Jimmy Sierra about the bigfoot coil situation, and it would seem that if and until he is able to find someone willing to take over the "handmade" operation, or some sharp engineer figures out a way to mass produce the coil, no more will be made. Too bad. Maybe someone could get them made in China where the labor cost is non-prohibitive. (I HATE that idea, but I also hate not being able to buy one). Whites won't take the job on because of the problems trying to mass produce something that, until now, has to be more or less hand-made.
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rage
retired