Simple solution to EMI!

CincinnatiKid · Dec 7, 2013

Hi all. My new Fisher F-70 is in hand. Electo Magnetic Interference seems to be a regular problem for this machine and others? I seem to have a solution!?
Today I visited "The Shack" and purchased item # 273-0105. This item is described as; a snap-on, ferrite data-line filter.
It highly reduces EMI, ( electro mag interference ).
Clip this small device near your control housing. You will be amazed at the lack of interference!
Thanks to "kascinoh" for my initial info!
Peace

CincinnatiKid · Dec 8, 2013

I'm not quite sure but the RadioShack tech says that this small device will "shield" any device it's clipped to. Field tests are forthcoming soon, although this device does quiet my machine indoors. Simply clip device to coil cable where cable inserts into housing. That's it, you're shielded!

Rob in KS · Dec 8, 2013

CincinnatiKid said:
I'm not quite sure but the RadioShack tech says that this small device will "shield" any device it's clipped to. Field tests are forthcoming soon, although this device does quiet my machine indoors. Simply clip device to coil cable where cable inserts into housing. That's it, you're shielded!

It doesn't really "shield", it just stops the interference from getting into the control box.
They are used a lot in radio. For example if you have alternator whine getting into your Ham /CB radio, it will knock that right out.

Does it effect your depth or signal strength? Some simple air tests might be in order.
It's too cold to do anything else !!

CincinnatiKid · Dec 8, 2013

Thanks for the info Rob in KS. I have preformed many air tests with device attached. I notice no difference in depth at all. True test will be in field though.
My main concern about this small device is why they're not installed from factory in current detectors? It can't do harm to circuit boards, it protects them. Doubt size or weight would be an issue either. And cost is low, $6.00. I will post field tests soon... Peace

Rob in KS · Dec 8, 2013

Air test will be a good indicator, since the only thing we are testing is ferrite on or off.
People put down air tests. It's the only we can compare detectors. I know it doesn't correlate to soil depths.

What is causing your interference? Power lines?

barrywk · Dec 8, 2013

I looked on radioshack website and they also have a smaller,less obtrusive one for 2.99

CincinnatiKid · Dec 8, 2013

Thanks barrywk, but if you go to "The Shack" in person as I did, you will notice the less obtrusive model you speak is to small to clip onto a detector cable. I suppose you could tape it to detector though? Peace

barrywk · Dec 8, 2013

They show two 0f the bullet shaped ones online....but if what u say is true kid then radioshack misrepresents them online because they say they will fit over coaxial and AC cords

XL-PRO PRO · Dec 10, 2013

The only EMI interference that I have experienced has been from electric fences.I can't help but believe that if a five dollar filter would eliminate this interference, every manuafacturer would ship their detectors with these already in place.

CincinnatiKid · Dec 10, 2013

Thanks again barrywk. I initially looked at the two smaller versions, but noticed neither would clip onto a coil cable. The one I purchased fits exactly and was only 3bucks more. The only reason I even looked into EMI is because of my new F-70 and it's "supposed" high susceptibility to it. I've not yet found this to be the case, except in my home with normal household emissions. The device did stop these. When I encounter field EMI, I will test and let you the results. Peace

Rob in KS · Dec 10, 2013

XL-PRO PRO said:
The only EMI interference that I have experienced has been from electric fences.I can't help but believe that if a five dollar filter would eliminate this interference, every manuafacturer would ship their detectors with these already in place.

That makes sense now. An electric fence will interfere with about any detector. A pulse running down a long wire which makes a great antenna. I'm surprised it filtered it out without hurting performance.

They don't put them on detectors because most people aren't around electric fences and they can cut a buck off the price. I usually avoid fences. They are just too trashy.

Your house is a soup of EMI. My PI makes funny noises inside. But I have to give it a tune up so its running in the shop.

I'm gonna remember this tip

Thanks

foiler · Dec 10, 2013

An in-line device can help to reduce EMI emanatiing from the coil and through the cable. It would have little effect on a radiated signal directly on the control board and circuits thereon. A faraday shield or cage would be more effective. Manufacturers could easily use shielded cable and embed wire shielding in the plastic control bodies. This would leave only the coil exposed to EMI effects. Perhaps said manufacturers through testing discovered that even with the shielding described here the exposed coil produced significant interference anyway and the cost of shielding wasn't justified. Its the only reason I can think that such a simply manufacturing fix isn't employed.

CincinnatiKid · Dec 10, 2013

Thanks foiler! Your response is very informative and helpful.

XL-PRO PRO · Dec 10, 2013

Rob in KS said:
That makes sense now. An electric fence will interfere with about any detector. A pulse running down a long wire which makes a great antenna. I'm surprised it filtered it out without hurting performance.

They don't put them on detectors because most people aren't around electric fences and they can cut a buck off the price. I usually avoid fences. They are just too trashy.

Your house is a soup of EMI. My PI makes funny noises inside. But I have to give it a tune up so its running in the shop.

I'm gonna remember this tip

Thanks

I haven't filtered it out.I have found that by using a different detector with a different frequency or by adjusting signal strength that I can sometimes work these areas.Most Civil War sites are on farmland and unfortunately electric fences sometimes go with the territory.However, I do very little indoor hunting so EMI there is seldom a problem.I just find it hard to believe anything that attaches to the outside of the cable would have any effect on the signal passing through it.I have installed inline noise filters to remove alternator whine from cb radios but the current actually went through the filter.But then again I've never understood how those pest control devices that you plug into the wall plug keeps rodents and insects away either(haven't seen them advertised lately come to think about it).

Rookster · Dec 10, 2013

Cool. How much and is it something to buy online?

foiler · Dec 11, 2013

The Minelab X-terra 705 I use has an EMI circuit in it. It identifies any interference to the machine then offsets the frequency to eliminate it. I've not experienced any EMI problems using the 705.

docbars · Dec 11, 2013

Cincinnatikid
Does your F70 have freq. shift? I can change freq. on the F75 and have very little trouble with emi. But I don't hunt in or around town much.

p.s.
read another of your post. Your machine should of came with the rubber bushings,coil cover,and Velcro. Call Fisher and let them know,they will take care of it.
HH

CincinnatiKid · Dec 11, 2013

foiler, you just became my "go to" for EMI info.
I have never used a Minelab, yet, and had no idea they solve EMI internally. This said, I do believe all machines will be effected at some point/place. My machine does have freq shift, but as I'm new to this machine, I wanted all bases covered.
Can you explain a bit more on how your 705 deals with EMI please. Peace

devilpookie · Dec 11, 2013

I bought one of the EMI filters like you are describing from Ebay for my ATP. There are a couple of spots on the beach when the detector would just start getting wacky making R2D2 noises until I would move away from the area. Changing the other frequency offset options did not help either. Installed the EMI filter. Did not make any difference.

CincinnatiKid · Dec 11, 2013

Thanks docbars! Yes my new F70 does have 7 different Hz shifts. In my limited use w this machine, they do work. But one of my favorite sites is beneath "humming" power lines. These lines have seriously effected every detector used there, to the point that detecting is impossible. I think this lil gadget just might work? I hope to detect this site Sat. I will keep you posted...
The accessories? Every site I check, list them as options/additional $. Even the new "Users Manual" that came w my F70 lists them as options? I think this is nuts! Rubber washers and a coil cover combined might cost $1!? I have fabricated rubber washers, but had to order coil cover. It's a shame a company like Fisher doesn't provide such simple things?
Peace