Need definition of symptom...

[IDXKevin]

As I sweep in all metal mode(audible threshold present) there is a slight rise in threshold volume as the coil accelerates into the sweep. Is there a term for this and description of exactly why it happens? I am a relative noob/lurker,sorry if this is common knowledge...
Thanks!

[joop]

Could it be related to the coil passing over ground?

[golfnut]

Hi, Joop is probably right, it sounds like your

ground balance is not set optimally,
To set it, put unit in Disc mode, turn GEB high (to maladjust it so machine will false) turn sens up (so can detect small things easier) and bob coil head up and down vertically over the ground, dont bounce the coil on the ground - but stop within an inch. Each bob up and down you will hear as tone.

Now, while bobbing, rotate the GEB control slowly and the tones should stop. At this precise pot position you have averaged out the ground signal - on the ground you bobbed over.

Having got to this point you go off detecting. Redo the ground balance every 10 mins as the ground minerals change in every location. When the geb is set very well you can raise the sensitivity control so you trip tone on successively smaller items. So they work together, I normally raise sens to max and GEB it, then decrease sens a tiny bit - to give a defined quiet level, rather than falsing on minute mineralisation or slight ground balance degradation as you walk off somewhere else.

Most modern machines once calibrated, track the ground signal return continously and almost in real time track the ground signal out - so the sens can be set high to see real small signals - because the elephant in the room - The Ground Signal, will be tiny.



you may be doing this on wet grass? These machines are susceptible to falsing over soil with wet grass, and wet beach sand. They love flat bare earth with low iron content.

If not the above the sheilding on your coil may be less than required ?

If you swing aggressively it may be that alone.

If the cable is wrapped loosely, it can move during the sweep and you are detecting the cable movement.

It could be flex in the stem, giving a short whip to the coil position in the sweep.

It could be the coilhead itself having poor stiffness, so the Tx Rx coil in relation to each other move slightly in the sweep.


You may have iron in the soil and disc not set to fully reject iron?

S

[golfnut]

"You may have iron in the soil and disc not set to fully reject iron?"

Sorry, you were in all metal, so there may be iron in the soil and your getting that - Set Disc to reject Iron as a test and retry.


You may be in PP mode?


You may have a build error where you left out the 100k pull up on the PP mos switch and so are stuck in PP

Your Tx frequency and Rx frequency may be too close to each other - this makes these units twitchy.

S

[IDXKevin]

Thanks so much for the timely replies, I will investigate all the solutions when the weather warms up here in a Wisconsin. I did not think this was normal. I am hunting more and more in all metal to try and catch the threshold variances on deeper/smaller targets but the condition I described is making that difficult. I don't have any falsing in silent search so I didn't really realize there may be a problem/misadjustment until I started using all metal a lot. The unwanted rise in threshold happens more with the 950 coil, not so much with the 5.3. This would of course make sense as the 5.3 is not picking up as much signal,I just have to narrow down the cause.