Troy Custom Detectors is no longer manufacturing metal detectors. As a tribute to Troy Galloway, Graphique Du Jour is
hosting a copy of his original website for his achievment in designing and bringing to market a the Shadow line of detectors,
with features and performance previously unmatched. Graphique Du Jour Home

Electrical Interference and the Modern Metal Detector
by James R. Williams

As the world continues to fill up with every conceivable electronic device and gadget that mankind can conceive, and now that most households contain at least one or more “wireless” devices of some sort it is no wonder that we are hearing more and more strange beeps, squeaks, squawks and gurgles as we attempt to detect our favorite spots.

If we can understand what causes most of this interference that is typically experienced by the detectorist then we have a better chance to successfully deal with the problem and be able to search any given area. The modern detector itself with its more sensitive circuits no doubt contributes to the problem, but then we all want and demand that “extra inch” from the designers and manufactures. Most manufactures attempt to deal with the problem the best they can. But if you are going to build a sensitive machine then sooner or later there will be a situation where some form of interference is bound be encountered.

It appears that the most common type of disturbances are from the basic 60 hz AC circuits and appliances in our businesses and residences. Two of the most notorious trouble makers are the halogen light bulb and dimmer controls. When the two are put together in a lamp of any sort it has the potential to be a serious problem. My experience has been that the Torchiere type floor lamps are among the worst. Another generator of huge amounts of electrical interference is the touch control type of circuit typically used in various table and bed side lamps. The bad thing about these touch lamps is they will often emit interference without even being turned on. Just being plugged in will often do the job. Some other items that have been known to cause these type of problems are door bell transformers, furnace burner igniters, air conditioner controllers and fluorescent light fixtures. The list goes on and on. Virtually anything that gets connected to the power grid has the potential of being a problem.

Although most of this garbage is generated by common household items, there are other sources as well. The power lines themselves can cause problems, especially the high tension types. Only one dirty and leaky insulator can wreak havoc for blocks around. Also electrical components in control boxes for traffic signals can be a problem and completely blanket with noise that vacant lot filled with buried goodies.

Most of the items so far mentioned are what we normally encounter in the urban setting. When out in the wide open spaces things are usually pretty quiet except for the occasional electric fence or cross country high tension transmission lines. These large cross country transmission lines at times can be devastating to a sensitive all metal gold detector out in some remote Arizona canyon.

Don’t despair all is not doom and gloom, given the amount of extraneous electromagnetic energy floating around us the chances of encountering this problem is less than one might imagine but it does happen and usually at the most inopportune time. As with most problems there are usually ways to deal with them and lessen there impact. The detector itself can be used as a very effective tool to deal with the situation. The detector is basically a receiver or detector of electromagnetic energy (that’s why you are hearing the noise in the first place). When interference is encountered just raise the coil three or four feet off the ground and while standing still, rotate the entire detector thru a full 360 degrees. The best way to describe this is to turn the entire unit as though it was a giant screwdriver. Then hold the coil at the same height and slowly rotate your whole body in a circle while performing this “screwdriver maneuver”. If the interference is from an external source, somewhere during these two maneuvers there will most likely be a spot where it will do one of two things, either get worse or fade into a null or possibly even go away. If you are unable to find a null even with the detectors gain set at minimum then it can be assumed that you are dealing with an extremely strong source . What you are doing is using your detector coil as a directional antenna or sensing probe. This operation will at least assist in determining whether the problem is external or a detector malfunction. A sure indication that the noise is from an external source and not a detector malfunction is if you hear the null indication.

By utilizing this procedure you can keep moving in the direction that causes the interference to become stronger, it is often possible to trace the offensive signal directly to its source (as in my case, that reading lamp by the couch). When you get very close to what ever is generating the noise you most likely will not be able to find a position that will produce a null even at the minimum gain setting, but it should get louder and more annoying as you approach.

In the event that the noise is being generated by a faulty power line, if the general vicinity of the noise source can be located by you and the power company notified they will usually be more than willing to remedy the situation. They had rather we pay them for their power than have it dribbling away into thin air across a bad insulator somewhere.

If the source of the problem cannot be located and dealt with, there is another way that I have found in many instances to be very effective. Remember the detector coil is an antenna, what about using a smaller antenna! That would of course be a smaller coil. As an example at my home we have a lamp in the living room with a dimmer controlled halogen bulb and when that lamp is on it is absolutely impossibly for me to operate either of my two modern detectors anywhere in our yard. That is unless I use a smaller coil. My primary machine is a Shadow X2 and with the standard 7 inch coil the racket it bad and with the 9 inch it is horrible, when I install a 4 inch coil for all practically purposes the noise has disappeared. I have experienced similar results with a Whites XLT using small coils. These small coils also work very well in locating the extremely strong noise sources that will sometimes completely saturate a larger coil.

Yes I lose a little depth and can’t cover the ground as quickly, but the point is that I can continue to hunt where as before it was absolutely impossible to do so. Now there will be situations where the problem will be so severe that even the smaller coils will be swamped with this stuff, that is probably a good time to start hitting the research material and find another spot.

If there is a spot you have an absolute burning desire to hunt and simply can not defeat the noise problem any other way there is another “last resort” solution possible. There is no way I would want to go back to these relics on a regular basis but you might try and get your hands on an older model machine of some sort. I have an old Garrett VLF Master Hunter and a Whites Gold Master, both early 1970s vintage and either of them will completely ignore the noise problems that I have experienced. Each of these machines certainly have their shortcomings, limitations and idiosyncrasies as compared to the more modern models, but again you can hunt in areas where otherwise you probably could not.

In review, using your detector as a directional finding device is one way to locate and identify noise interference. If this does not work try use a smaller coil which will force you to search a little more slowly and carefully.

A lot of good finds have been made with small coils. If none of these suggestions work, get a beverage pleasing to your taste, relax and hit the books. Or possibly better yet temporally forget the whole thing and invite someone close to you out for a nice dinner and evening on the town.

Reproduced with permission from James R. Williams
© 2003 All Rights Reserved

Webmaster - Shadow21