Has anyone tried one of these Coil Filters?

[Fisherfinder]

I was wondering if anyone has tried one of these coil filters.

They are supposed to help filter out EMI, much the same as the ones that are often seen on computer cables.


[attachment 210403 coilfilter.png]

 

[DirtyDeedsDugDirtDeep]

I was wondering the same thing.
Could just be a gimmick ??

 

[Larry (IL)]

This should answer all your questions: http://www.findmall.com/read.php?22,1291783

 

[Fisherfinder]

There is one place here in town that I search, (a sand box), and only 15 yards away there is an electrical sub station.

The first time I went there my 1235X went nuts. It would not stop chattering. The closer I got to the sub station the worse the chattering got, to the point I could not use my machine.

I have since tried one of those filters but I was using a different coil.
I experienced much less chatter, but a true test would be using the same coil I had used the first time

I asked the dealer what his experiences were and he replied.............


Seems to depend a lot on the type of detector, conditions, and the source of the noise causing issues.

I've used it on an Fisher F75 and Teknetics T2 with mixed results.

I have gotten good repors from people using them on:
Minelab Sov., GP & SD models.
Fisher F2, Gold Bug.
Garrett Ace 150 & 250

Seem to work better on models with plastic control boxes (less shielding for the electronics).


I will post here when I try that filter on the same coil I used the first time I had the problem.

I will post a photo of that damn electrical sub station, you can actually hear it "Buzzing".
.

 

[Larry (IL)]

Try it and see is the best policy but the effectiveness will depend on the source of the interference. The toroid coil filter is designed to suppress RFI/EMI for 25 MHz to over 500 MHz sources. What you are experiencing with the power station is commonly known as 60 cycle hum or 60 Hz EMI where I think the filter would have little or no effect, but stranger things have happened. I have one on the coil input of my V3i and it has made no difference whatsoever.

 

[Fisherfinder]

I just ran an errand close to that park.
Here are pictures of what is giving my machine fits.

Actually it is closer than 15 yards.


[attachment 210502 AAAA002.jpg]


[attachment 210503 AAAA004.jpg]


This is the place I found the most valuable item I've ever found

A miracle really, through all that chatter, and dealing with all those steel poles........

It pays to use headphones, literally.
.

 

[Ronk]

I recently posted about this subject with no replies but that's fine.I'll say it again anyway.All of my detectors with a Metal Case are the quietest also the older ones I've had in the past with Metal cases have always been super quiet compared to my ones with the Plastic cases! A lot of manufactures refuse the shield the inside of the Plastic housing for their own reasons.Even the detectors with higher gain will be a little quieter with proper shielding and that also includes proper shielding for the cables and the coils.Highly Sensitive electronics NEED some kind of shielding these days with all the EMI that's around us.Detectors are not stationary as they go to difference locations especially in or close to town where most of the EMI occurs.
To Me it just doesn't make sense to not shield a sensitive electronic device.That little very tiny area inside the box of some circuits with shielding paint is next to useless and does very little to nothing to protect.Maybe it just cost too much to shield things these days.The copper tape is great for shielding anything! I use it in electric guitars to cut down on noise and it works great and you can solder to it. You just have to make sure you don't create what is called a ground loop or the noise will be worse.
To me shielding in electronics is very important!

HH!
RonK

 

[Fisherfinder]

Ron, you are reading my mind!

I just came back from talking to the guy who helped me a bit with the problem I was having with my 1235X.

The problem started "The night I detected at the sand box pictured above". Along with all the chatter I lost 90% of
the audio to my headphones. Pull the plug, speaker worked fine. Tried my other headphones, same problem, only
a ghost of the audio could be heard via my headphones, and only when they were turned up full blast.

Last night while searching a totlot a few miles away, with my headphones turned up full, with a rushing sound
my audio came back to normal, had to reach up and turn them down.

When I mentioned this to the tech, he said Ahhh, there is a coil on the board that likely had been "Magnetized".
When it lost it's magnetism the circuit returned to normal.

He also said to "Avoid" high power lines, electrical sub stations, and the like, that areas like that can screw up
the circuits in a detector.

I was sitting here thinking how to line my box with some thin copper sheet when I saw your post.

I found a source for that copper tape...
http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Shielding/Conductive_Copper_Tape.html

Also a call to Electronic City here in Burbank,CA payed off.
http://www.electroniccity.com/

They have packages of two pieces 3 1/4" wide X 10" long for $6.25

That may be just the ticket to shield the box on my 1235X

.

 

[Ronk]

It won't do any harm to try it.Just make sure the tape doesn't touch anything else in the circuit or any other wires or switches.Sometimes you can run a ground wire from the ground on the board to the copper tape but I wouldn't do that unless you know what you are doing.Just putting the tape on the inside of the plastic housing might improve things but there is no guarantee.The main thing is "Make sure the tape doesn't touch any part of the electronics or you could Kill the detector! I have never seen the inside of a Fisher 1235x but I had the 1236x but sold it because I hated the VCO pinpoint on it.It was too annoying for me! Everything else on the detector I liked.
Just be "EXTREMELY CAREFUL" if you try to shield the detector. If you have any doubts at all you might see if someone you know that is experienced in electronics to do the job for you. Hope some of this helps.

HH!
RonK

 

[Larry (IL)]

That is a good idea but the shielding has to be grounded to do any good, the battery negative would be OK.

 

[Ronk]

n/t

 

[Larry (IL)]

Sorry, I must have misread your comment:

"Sometimes you can run a ground wire from the ground on the board to the copper tape but I wouldn't do that unless you know what you are doing. Just putting the tape on the inside of the plastic housing might improve things but there is no guarantee."

 

[Ronk]

I don't know of any Specifically made for metal detectors but I know they are used on computer and office equipment like Monitors,Scanners,Fax Machines,Printers,Modems, and other similar items.Some have claimed they worked ok on their detector and others have said they did nothing.It's possible they could work only in certain areas but not in All areas.Just like the detector itself without a filter.It's really hard to say.If it DID work on one detector that doesn't mean it will work on all detectors.It's possible that the frequency of the detector could play a small role as to how the filter performs but not many has used them enough to draw any conclusions.Like a few have already stated...I can put up with a little chatter as long as the performance doesn't degrade.If it chatters too much then lower it just enough till it stops.I still think a metal detector should be shielded and that includes the Cabel and Coil.More than likely the cables probably are but how good..I don't know unless I cut one open to see.Most coils should be what is called "Electrostatically Shielded" or Faraday Shielding which is metal foil of some type around the windings of the coil and is suppose to reduce or stop noise from wet grass and the like.Although some use the metallic paint on the interior on the coil housing is suppose to do the same thing.The Metal Detector Circuit Board itself Definitely Needs to be shielded to some degree at least as much as possible.

HH!
RonK

 

[Fisherfinder]

Thanks Larry, I was wondering about the neg of the battery, that makes sense.

I have an idea......

Since it is going to be a chore to get my hands up inside that box, especially with the sticky tape grabbing every time it touches somewhere,...........

I may make a snug fitting liner that just slips into the box out of thin card stock or plastic. Then I'll apply the copper tape to to the outside of the liner, that copper tape is only a little over .001" so maybe I'll put two layers, that equals about .0025", I'll look and see what the electric guitar builders do when it comes to thickness.

Then ground it, that copper tape can be soldered, and then just slip the liner in and button it up.

If some one wanted to they could do a nice clean job of covering the outside of the box, then spray it with several light coats of that rubberized paint, the one you use for lawn furniture.

The city I live in is very hot with EMI.

There are several places where it even messes with the our car radios.
.