False beep at end of swing

[6666]

Hi Qiaozhi
just a question about PI 1-4
because these circuits dont have earth field cancellation like in the surf pi
do PI 1-4 give a false beep at the end of a coil swing ?
thanks

[Qiaozhi]

Hi Qiaozhi
just a question about PI 1-4
because these circuits dont have earth field cancellation like in the surf pi
do PI 1-4 give a false beep at the end of a coil swing ?
thanks

The Earth Field problem will be present with PI-4, but since it is a simple design with a relatively low gain, the effect will be reduced.
I guess you're asking this question as a comparison with the PI Polish, and the same applies in that case. Also, the Sandbanks design (on which PI Polish is based) does not start sampling until 50us. This, combined with the low gain, may also reduce the Earth Field effect somewhat.

With designs like MPP, Baracuda, Hammerhead, Delta Pulse, etc., you must include Earth Field Cancellation due to the high gain.

[6666]

AHH of course late sampling, completely forgot about it, over the last few years I've been so obsessed with concentrating on super fast coils, less than sub 10uS sampling for tiny gold and ground balancing, late sampling and the effects it can have slipped my mind, thanks for the memory jogger

[Carl-NC]

I don't see why late sampling would affect Earth field pick-up.

[Qiaozhi]

I suspect the lower gain would make the Earth Field effect less evident, But, as far as a later sample is concerned (on second thoughts) this will still contain the same amount of signal wherever you sample. So the main reason must be the former.

[homefire]

My guess is your ark of the swing is changing the distance from the ground. That is the issue. Just swing the detector as your suppose to wide sweeping level to the ground and it won't be a issue.

[daverave]

My guess is your ark of the swing is changing the distance from the ground. That is the issue. Just swing the detector as your suppose to wide sweeping level to the ground and it won't be a issue.

i had the same problem with all my surf pi's and i found its a magnetic field of the earth problem...you need to add a balance control as in the hammerhead...and precisely adjust using a ring magnet to cancell the earth mag problem.

[6666]

i had the same problem with all my surf pi's and i found its a magnetic field of the earth problem...you need to add a balance control as in the hammerhead...and precisely adjust using a ring magnet to cancell the earth mag problem.

Hi Dave thanks for the info, did you watch the signal on a scope or just listen to the audio ?

[daverave]

i just listened to the audio while rotating ring magnet several inches away from coil.