EMI and the Sovereign

[lloyd0161]

I have the Sovereign XS-2. In my neighborhood this detector rarely can be used do to electromagnetic interference. At the end of my yard I can barely use it even with the lowest sensitivity setting. There is a rythmic pulsing sound when in all metal and random beeps and nulls when in discriminate mode. At the local park about 1 mile away the situation improves but in some areas of the park I need to dial down the sensitivity.

1. Anyone else have similar issues?
2. What are the sources that could cause this besides power lines?
3. Any way to lessen the effects?
4. Do the Sovereign Elite or GT handle EMI any better?

 

[babulin2002]

hi
i have the gt and in some areas i experience exactly the same symptoms as you described. don't think there's a way to get rid of it, just have to change the place. i think it is the power lines, sometimes they are underground and hence not visible. not sure if other cables, like phone lines, also give as strong an interference.
cheers

 

[kered]

I got my XS2apro given(non working) when i opened the box there was no insulation screen on the electronics once fixed i tried it and it was very unstable, a screen made from foil was put on and it cut out almost al emi here at home, try having a look inside, i seam to remember the first units didn't have the foil screan, also the wire to it may have come undone as its conected with a paper clip and easily tears loose

 

[crazyman]

Certain frequencies are more affected by EMI than others. My understanding is that Minelab uses different frequencies to compensate for ground minerals and I might be wrong but I think to some degree maybe those frequencies change depending on the mineralization and that frequency change might be affected more by EMI. Low frequencies operate better and handle minerlization better than high frequencies. lower frequencies also seem to be less affected by EMI from my experience so maybe the Sovereign uses a higher frequency or frequencies in good ground than it does in bad ground and the higher frequency might be more affected by the EMI in your area. That might explain why some people don't have the amount of EMI problems others seem to have. That's just a guess on my part but there is more to how Minelab uses different frequencies than I had thought. I have no EMI problems and I have some pretty bad ground.I had once thought the iron mask feature was nothing more than a expanded discrimination range switch similar to the black sand switch or the the hot rock accept/reject switch found on some Whites detectors but I think it's more of a frequency shift that uses a certain frequency or frequencies that allow certain size iron to bleed through the normal discrimination range making it easier to see other targets close to iron. Iron mask seems to affect the sensitivity setting around EMI also. You can see this by testing in your house where there is a lot of electrical interference. Turn off iron mask and turn your sensitivity up until it starts to react to the interference now turn it down just until the detector is stable with a steady threshold. Now switch iron mask back on and I think you will see the difference. In my tests the sensitivity setting can be set higher around electrical interference with iron mask off and needs to be set lower to get the detector stable again with iron mask on. I've been wrong before though!

 

[lloyd0161]

I will need to open the box and have a look inside for EMF Shielding. I thought of this and will try to add this if not present. I tried a ferrite choke on the coil cable but this did nothing to help.

 

[UK Brian]

A combination of design factors I'm afraid. Multifrequency uses a square wave created by taking a sine wave and adding harmonics.
Using harmonics creates various design problems due to the increased sensitivity to iron and external noise. Thus the Explorer has both iron mask and noise cancel.

The shielding (pre GT as I haven't opened one of these up) went from none to having a open ended plastic box with a thin wrap of foil round it. My XS-2 was not earthed. A Fisher CZ has a thick copper foil shield thats earthed by means of a paper clip and wire. I haven't seen earthing on the XS-2's but they need it. I scrapped the foil covered box and shielded the whole of the inside of the control box except the reverse of control panel face which would be to difficult so at least the circuits don't face unprotected towards the coil.

As I said i haven't been inside the GT but is does cope rather better than the older Sovereigns.

 

[Art (NWOH)]

BBS operating frequencies are harmonics of both 50 and 60 hz power line frequencies. Single frequency detectors use a frequency that is chosen to NOT be a harmonic, so interference from power lines is usually less with them.

You can also get interference from other sources, but in most cases it will be from the power lines.

Don't feel bad. I have been in some really severe areas too.

HH

 

[lloyd0161]

Thanks guys. I did open my XS-2 and found the open ended box with a thin foil and paper clip ground. Where do I find the heavy copper foil? This is becoming a challenge. I am bound and determined to alleviate some of the interference.

 

[lloyd0161]

I tried wrapping the entire outside of the box with foil and grounding it to the inner shield. This did nothing to alleviate the issue. All of the detectors that I have owned have had electronic interference issues in this yard. The Tesoro Vaquero could not be used. The X-Terra 305 is hit or miss depending on the day. On certain days it was unusable as well. The Garrett ACE 250 has done the best of all. With the sniper coil no issues. With the 6x9 coil sensitivity of 8 no issues. Anything higher and unusable. With the 9x12 coil sensitivity of 3 or 4 and same depth as 6x9 coil. The ACE has cleaned out my yard with the exception of one war nickel which the X-Terra found. The Sovereign has yet to work at all in my yard.

 

[Art (NWOH)]

There are some problems here.
Noise gets in through the coil and cable as well as the box.
There are three kinds of fields that are unwanted. Electric, magnetic, and electromagnetic. They are all different in behavior.
Electric and magnetic fields are anchored to the source. Eletromagnetic goes into free space radiation with no connection to the source.
Electric and electromagnetic fields can be blocked by common metallic shielding that is grounded, but magnetic fields are not phased by anything but ferrous shielding. It passes right through everything else.

If magnetic interference is the main problem, then you can not escape it .

HH

 

[JHM]

Check the wire going to the foil shield inside the box. Mine came loose and made it act like a bucking horse. Interference everywhere. Worst thing I've found to cause EMI is a central air conditioner. I fan hear the fan running through the speaker in my Tejon when it kicks on.

 

[lloyd0161]

Check the wire going to the foil shield inside the box. Mine came loose and made it act like a bucking horse. Interference everywhere. Worst thing I've found to cause EMI is a central air conditioner. I fan hear the fan running through the speaker in my Tejon when it kicks on.

I already checked this. it appears to have good contact. I made sure of this by moving it around and creating fresh metal where it looked like it had oxidized a bit. Still no luck. I really wish this detector would work because I know there are still some older coins to be found.

 

[UK Brian]

All proves that its not a Sovereign E.M.I. problem as all your detectors suffer to varying degrees. Thing to do is select a machine that uses a frequency well away from the standard ones as shielding can only do a certain amount as most is picked up by the coil or one that will actively find the EMI frequency and then ignore it.

 

[Critterhunter]

On the GT sometimes switching from the normal band 2 everybody seems to use (to keep the IDs the same as older Sovereigns for the most part) to band 1 will eliminate the nearby noise. That being said, I haven't found the GT to be any more prone to RF noise than any other machines I've owned and used. Older Sovereigns (some of them) came with no shielding depending on the production run. Wrap it with foil (don't short anything!) and put a paperclip on the foil and then attach that to the ground. When I had my GT open for my remote pinpoint switch mod I noticed no shielding in the front or back of the unit, just around the board. Seems shielding those would make it even less prone to RF.

Some say egg shaped coils like the SEF coils will reduce RF noise too. Might want to try a 12x10.

 

[lloyd0161]

I have found that the XS-2 works ok in all metal and will work anywhere in my yard for the most part. The threshold is not a nice steady hum but it works. Of course I will need to dig everything. It is just when placed in discriminate that the EMF prevents it from working. When I get out to the park about a mile from my house the detector works flawlessly.

 

[kered]

You could try using the all metal to locate the target then shift to disc, knowing exactly where the target is the sov should lock on to it and overcome the emi present, at least you know its not a false emi target and something is there, should cut out the amount of iron you have to dig in the yard too

 

[lloyd0161]

You could try using the all metal to locate the target then shift to disc, knowing exactly where the target is the sov should lock on to it and overcome the emi present, at least you know its not a false emi target and something is there, should cut out the amount of iron you have to dig in the yard too

Good idea. I also went back to hip mounting the detector. I made a bag from a fabric lunch bag which has some sort of metallic fiber looking plastic liner. It is also somewhat waterproof from rain. Anyway, once in the bag the EMI was lessened a bit. Using my yard as a test bed for dealing with the EMI has been a challenge but maybe I will come to some compromise through trial and error and be able to hunt other bad areas. I also tried wrapping the entire upper rod assembly with cable wound around and control box in heavy foil and grounding this but did not work.

 

[Critterhunter]

That's a good idea- shielding a carry bag to stick the GT into.