Tweet
Hi Exciter,
Yes it is possible for a coil to give false signals when bumped. Usually, what happens is the coil lead moves rapidly and it is sensed as a target. This is more common when regular coax is used and the delay is very short.
A quick test of the coax is to simply thump it without moving the coil itself. If you get a false signal, then the coax is most likely the cause.
Now, if the coil is right on the edge of working then it can be hypersensitive and when operating that way, it can respond with a false signal because the windings move ever so slightly. You might try turning the delay back just a little and see if that helps eliminate or at least, minimize the problem.
Also, try to make sure the coil lead goes up almost vertically at least for a short distance and is not allowed to move or wiggle easily.
BTW, this is not an uncommon problem when first building coils and trying to operate at the shortest delay possible.
There is one more possibility and that is the earth field effect is causing the false signal. This will usually occur when the coil is moved quickly and the gain of the two signals is not the same at the differential integrator. It was found out that the gain drops off at delays of less than about 13 usec or so, when the gain of the preamp is high. What actually happens is the sample taken at the short delay is not amplified the same as that taken at the later delay. This becomes more obvious when using TI brand NE5534A's.
Reg
Yes it is possible for a coil to give false signals when bumped. Usually, what happens is the coil lead moves rapidly and it is sensed as a target. This is more common when regular coax is used and the delay is very short.
A quick test of the coax is to simply thump it without moving the coil itself. If you get a false signal, then the coax is most likely the cause.
Now, if the coil is right on the edge of working then it can be hypersensitive and when operating that way, it can respond with a false signal because the windings move ever so slightly. You might try turning the delay back just a little and see if that helps eliminate or at least, minimize the problem.
Also, try to make sure the coil lead goes up almost vertically at least for a short distance and is not allowed to move or wiggle easily.
BTW, this is not an uncommon problem when first building coils and trying to operate at the shortest delay possible.
There is one more possibility and that is the earth field effect is causing the false signal. This will usually occur when the coil is moved quickly and the gain of the two signals is not the same at the differential integrator. It was found out that the gain drops off at delays of less than about 13 usec or so, when the gain of the preamp is high. What actually happens is the sample taken at the short delay is not amplified the same as that taken at the later delay. This becomes more obvious when using TI brand NE5534A's.
Reg
Comment