Surf Pi 1.2 depth response

[Freediver]

Hi all,

I just finished a Surf Pi (my first detector project), that I bought from Silverdog's shop and when testing it in air I have found that I get a consistently strong tone from 0 cm to about 15.5 or 16 cms with a 1 euro coin. Between 16 and 17 cm I get a weak tone and after 17cm absolutely nothing. I had assumed that the tone would reduce gradually as the coin moved further from the coil but it does not. It dies in a very short range between 16 and 17 cms. Can anyone tell me if this is normal for this kind of detector? (I built a flat spiral coil 32 turns about 120mm ID and 175mm OD with enameled 24AWG)

[jap]

Hi all,

I just finished a Surf Pi (my first detector project), that I bought from Silverdog's shop and when testing it in air I have found that I get a consistently strong tone from 0 cm to about 15.5 or 16 cms with a 1 euro coin. Between 16 and 17 cm I get a weak tone and after 17cm absolutely nothing. I had assumed that the tone would reduce gradually as the coin moved further from the coil but it does not. It dies in a very short range between 16 and 17 cms. Can anyone tell me if this is normal for this kind of detector? (I built a flat spiral coil 32 turns about 120mm ID and 175mm OD with enameled 24AWG)

Hi Freediver
its normal, see photo i hope it help.
best time
j.

[Freediver]

Hey thanks for the diagram Jap, now I can start experimenting with different coil geometries.

[xycy]

Hi,
I have Surfmaster Pi. The value of R28 in it is 240k. Is it OK or I should use 210k? What if I use 51k? Also I use for R2 4k7 and the freq. is a little lower. Are these changes for good or not? Should I use 5khz to improve the detector?
Regards.

[6666]

Freediver some of the early kits had the value of resistors R18 and R22 swapped did you get them in the correct holes ?
the wrong values made quite a difference to the depth.

I just did a quick test with my surf pi for you, my nicad pack is down to about 8 volts
but with a simple 20cm round coil
I can get a 1 euro coin made in Spain at about 25cm
that's in the air only.