SURF PI DELAY POT PROBLEM

[daverave]

When i turn the 100k potentiometer fully anti clockwise the sample pulse go's to far near the falling edge of the tx pulse...so im having to adjust a tad clockwise to get the sample in the best position...i want it so when control is fully anti clockwise the sample is in the right position...i noticed on a friends dual field this control has a click which puts the sample in the correct position...pls can anyone advise ?????

[Waikiki_Sweep]

100k is wrong idea at all. If you have properly build coil than it will work with 10k.
Your friends dualfield has even smaller delay - less than 20 microsecond.
100k in maximum position is eqal 100 microsecond of sample delay. It is too big. Good to find cannonball.
For gold you need as small delay as you can set (lower resistance on your pot) and your detector keep working without falsing.
Check your pot what direction you need to turn to reduce resistance. ( 1 kOhm = 1 microsecond. Add 15 microsecond from permanent resistor 15k in series with pot )
Get some small gold ring and try to find delay position that gives you maximum detecting distance in air.
Because it is something near 10-20 k then your 100 k pot is useless to find exact position.
Replace it with 20 k. If it is not working at 10 k position than coil is badly made and decays to slow.

[6666]

You can always solder resisters or pots in parallel with the 100k pot to bring the value down, saves unsoldering.

[daverave]

when i adjust the 100k delay pot i can get really close to the decay curve and the detector becomes so sensitive that the depth on small items is really good but if i turn it just that bit more then the sample lands up very close to the falling edge of the tx pulse and then i loose sensitivity...im not having much luck with this problem.