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New member
your right the tiny bits of foil are a problem using 8 uS,on the wet sand i find 8 uS has good benifits for very small gold items,im thinking at sometime of experimenting with 5 uS which should be very interesting,ive found that making a 12" coil to work at 8 uS works well on wet sand,but i made a 14" coil to work at 8 uS and depth is amazing but the ground effect can sometimes be a problem.


New member
As I understand it, commercial metal detectors for scanning food and clothing for metallic bits such a broken OBN needle points, bits of staples, etc operate at 2us or so. It occurs to me that if careful design of detector and coil can reduce usable pulse delay of the TDI to 5us, that new designs might be able to produce even shorter pulse delays. While foil might make beach use impractical, gold nugget hunting might benefit greatly - of course, there is the issue of bird shot in lots of nugget hunting contexts, but in some locations like Africa, where less shotgun usage has occurred, it could be a game changer.


New member
i found that its mainly the coil and getting the coil damping correct is what gives a low delay,the main parameters are coil wire,coil shielding,cable,damping,to get a low delay,thats what ive found by experimenting,so even a tdi can be modified to work down to 8 uS and maybe even to 5 uS,i compare it a little like radio,a good aerial will get those weaker signals,and what is a pulse coil ??? its in essense a aerial which transmits and receives,so get the aerial correct first to get good proformance.

Jim Robertson

Active member
ive seen a video showing a tdi pro detecting a nickle at 18" would that be a loud signal or a whisper or slight change on threshold or strong signal ???
I feel like there are a lot of things that are different on every beach no two are a like. I think in some conditions it is possible but not every beach for sure.


sand, white or black
already makes a big difference
on this video, I take out a beautiful ring at more than 15 '
I have several friends who have tdi
I rarely see them digging as deep = in this type of sand ..

the first 200 tdi pulscan (with number plate)
its able to fall to 8us see less
if you have the coil capable of doing it

then there are other problems
most important = noise
each parasite makes you lose a whisper
and each whisper can turn into gold :)