HALO EFFECT PROBLEM

[daverave]

ive just been testing my surf pi that i constructed and i went on the local beach but some of the targets that i dug dissapeared....ive read that this problem is called halo effect....what is causing this to happen ????? have i got something wrong when i made the detector....ive had this problem sometimes with normal motion machines but why with pulse detector ?????

[Ferric Toes]

Hi Dave,

Is this on the wet sand? If so, then there is an explanation. Wet sand on a sea water beach is conductive and the pulsed field from the transmitter causes eddy currents to be generated in the wet sand. This has the effect that to the object the TX field is enhanced. When the sand is disturbed by digging, this enhancement disappears and hence the object signal weakens, and maybe even disappears if it was weak to start with. This is not a halo effect as commonly described, but is well known when hunting in a sea water environment with a PI detector. In favourable conditions you can get an additional 10 - 20% more range than for an 'in air' test.

Eric.

[daverave]

would i have to make the sample pulse later to stop this problem....i did read that halo effect makes small items bigger to the detector...i wondered sometimes if im detecting a tiny object thats made bigger to the detector then when i move the sand the halo effect is gone and the tiny object is now too small to detect.

[daverave]

forgot to mention yes wet sand...i already get ground effect cause my sample delay is very early but the signal im getting is like a coin or ring very good strong two way signal but dissapears sometimes after digging.

[Waikiki_Sweep]

Also once you start to dig something you can change target orientation.

Coin or ring that lays flat gives you strong signal from long distance because eddy currents circulating over perimeter of ring or coin.

But when it stays on edge detecting range decreasing in two - three times because there is not enough area to create eddy currents loop.

If colored targets acting like transformer loops ferric targets acting opposite way like transformer cores.

If nail stays vertically you can hear strong signal from long distance because ferric nail acting as a core for your coil accumulating magnetic field and returning it after flyback.

If nail lays flat the signal is weak or you can hear double beep (detecting its ends where field is strong). This orientation is not so good to act like a core for the coil.

Try to pinpoint target better and dig deep. Or if target has lost move the sand to let it rotate and get better position.

You can't believe how orientation is important for successful recovery of target.

Once my wife has been asked to find heavy gold ring in small sand area that was lost 10 minutes ago.
She does not find anything after two attempts of full coverage of the area in different directions. Sand was dry, soft and deep.

So she asked ring owners to mix sand by hands knowing that effect of orientation influence.
Ring was found in few minutes and signal was very strong and loud. Target just went to flat position as result of sand moving.

Sometimes I can find rings that lost on ocean bottom only after 2-3 days because when people walking they mixing sand and changing targets orientation.
In one hour they can push gold ring to 8-10 inches down and put it on edge making it undetectable.

- I lost ring.
- Where? I checked area three times. Nothing found.

[daverave]

i guess like you said it maybe orientation with the target changing position...i use to get the same problem at times with motion detector...its just frustrating locating target at times.

[golfnut]

I tend to kick the soil or sand out to a big area to make it easier to locate,

do you use a garrett probe? these are reasonably good.


With some VLFs you can dig for something which disappears - then you sense the edge of the hole you made!

S

[Carl-NC]

PI detectors are very good at detecting tiny rusted fish hook shards. They go right through a scoop and if they fall at the right orientation can become invisible.

[daverave]

thanks to you Carl and the other guys for your help...pulse is so sensitive even two the tiny rusted fish hooks that carl mentioned...i just started using pulse instead of my tesoro motion machine and i must say im enjoying pulse but some of the signals im getting are far too deep for me to dig...im having to leave deep targets as the holes just keep filling with water.....ive had to put a high/low sensitivity switch on my pulse machine to reduce depth which i know is defeating the purpose of a pulse machine....sometimes i find the audio blares at me as the auto tune does not instantly recover...not sure what causes that.