Question about the 9 x 8 coil

[Billsie]

I recently bought a new 9" x 8" standard concentric coil for my Bandido uMax. In testing it, I find that I get no response when I swing the front toe of the coil over a target. In other words, if I swing the back or middle area of the coil over a target, it sings out loud and clear, but is silent if I swing the front 3" of the coil over a target.

Is this normal, or do I have a defective coil?

Thanks.

 

[tvr]

I just fired up the Cibola to check it out since it has a 9 x 8 mounted. Found no difference front edge verses back edge. If the coin is near the coil (like half an inch), I get a response all the way to the inside edge of the outer rim of the coil; for the entire circumference of the coil. As I get further away I need to get closer to the center of the coil to get a response. Further away it gets, closer to center it needs to be to get a response. Can almost visualize the cone shape. I swept the coin from all directions around the coil.

I was testing with the coil in the air, away from anything that might mask.

So a thought; when you tried it, was the coin on the ground? Did you move the coin to another location and try it again? Did you walk around the coin as you swept and tried it from different approach directions? The thought; actually theory: if where the coin was sitting had a piece of iron near, say 6 inches or so behind it, it could have started masking the response to the coin and seemed like shutting down on part of the coil.

Just a thought, on masking.
Cheers,
tvr

 

[Hombre]

Hi Billsie

It's kind of hard to diagnose your problem without knowing the specifics of your test. Was the target (coin?) on the surface of the ground, or naturally buried, or just recently buried, any Iron around it, etc. Also where your Disc. was set and if ground balanced properly. It came stock with the 8" brown coil, do you still have that to test with? There are lots of variables that you can try, like moving the target to a different spot to test.

 

[Billsie]

Hi tvr,

Thanks for your comments; they were helpful.

I have now had the chance to try a 9 x 8 coil belonging to someone else. Operating them both under the same conditions, it appears that my coil is indeed defective. Back to the factory it goes.

 

[tvr]

Thanks for the update on how things are. I was kind of wondering. Seems like a strange failure mode, but I guess some mis-alignment in the wire loops when the coils are wound could give a strange, asymmetrical pattern.
HH
tvr