Audio anomoly

[Squirmingcoil77]

I was out at a local high school soccer field the other night, and wasn't really finding much. I did, however, encounter a strange audio response from my X-terra 705. I had the sensitivity set around 15 because a lot of the targets were shallow and the ground was rock solid. I could barely dig three inches without my hands starting to hurt.

Anyhow, as I was sweeping the coil I heard a very faint buzzing sound, almost like feedback through an amplifier. It wasn't the null of the threshold or a quick target signal, it was just a very faint electronic buzz. I was in disc. mode with -8 through -2 and 48 notched.

So I went over the area again and pumped up my sensitivity to the lower 20's and got a very jumpy signal. I dug it up and it turned out to be just the top sliver of a pulltab about two inches down.

Has anyone ever experienced this type of noise and is this common? I've never heard it before.

Thanks for looking.

 

[Squirmingcoil77]

Guess I'm the only one that's experienced this. That's why I love my 705!

 

[Digger]

I've not experienced that exact situation. But it sounds to me like you may have two different things going on at once. With the Sensitivity set at 15, it is possible that you wouldn't have gotten a "solid" signal with the small portion of the pull tab. Detectors bounce their signals off of surface areas..... and the irregular shape of the pull tab top doesn't offer much of a solid surface area. Regardless, the noise you've referred to sounds like some EMF or RFI. I know I've hunted a few yards that would give me some weird intermittent sounds.... nothing that was consistent in pitch, duration or location. As you said, kind of like a faint feedback from an amp. A couple of them turned out to be the wireless network the people had in their house. I never figured the other one out, for sure. But I suspect it has something to do with the "invisible" electronic dog fence that was buried around the perimeter of the yard. HH Randy

 

[Squirmingcoil77]

I really appreciate the reply, Randy. I had never experienced that before, so your info is good to know. I'm always experiencing something new with this machine.

 

[Digger]

If it happens again, change Noise Cancel channels. You might be able to neutralize the interference by tweaking the freq a bit. Changing the NC will do that. HH Randy

 

[Squirmingcoil77]

If I ever encounter that again, I'll try that. Thanks!

 

[Old Longhair]

From my experience.......

A possible explanation for the pulltab reacting that way, might seem a little bizarre, but it could have been collecting a static charge from something that your detector didn't notice....aluminum does that.

Let me relate a short story. I had a friend of mine stop out to visit me when I lived in Colorado. And while he was there we took a trip up to the top of Pikes Peak. The view really is something, especially when there are storm clouds around. An electrical storm moved in while we were up there, and as the cloud enveloped the top of the mountain we headed for the car. On the way to the car, I asked my buddy if he heard a buzzing sound, and he said that he didn't. When I got into the car, the buzzing sound that I was hearing stopped. And as soon as I stuck my head out above the top of the car it started again. Hmmm...
It took me a minute, but I finally figured out what it was. I had my sunglasses on top of my head (it was foggy....we were in a cloud), and the frames were collecting a charge and arcing it to my head where the plastic on the ear part of the temple piece ended....right in front of and above my ear. Small wonder that my pard couldn't hear it.

Anyway, there may have been stray electricity being collected by that pulltab from either underground or overhead power lines. When you NC'd, it chose a channel that took care of the power line noise, but may not have picked one that would knock out the harmonic excitement that it was causing the pulltab. I've found fences (especially the ones that are aluminized or galvanized) that collect a charge, and often act similar to an antenna, in that there are certain places around them where the interference is directed or reflected to.

As for data streams. To me they sound like exactly what they are. If you've ever put a data CD in an audio only CD player, you have an idea what it sounds like (only in multi-tone), and nothing else has the same type of rhythm. The closest would be an underground fence. They just cause pandemonium. Electric fence chargers are easy to identify, because the UL approved ones pulse. Weed-burners have a drawn out pulse, but it is still a recognizable pulse pattern. Cell phone issues are periodic, and tend to follow a pattern that you can learn to recognize.

The only thing that really buzzes consistantly, is bad plug wires or the lack of resistor plugs on cars and small engines. The arc from a bad wire can put a hunt on hold for as long as it is present. Usually if it's a car, it either leaves or gets turned off ($4/gal gas makes people want to turn 'em off). But the mower w/o resistor plugs that's cutting the grass at the park you're hunting is going to be there until he's done, and since you probably can't cancel him out, you might as well go get lunch and come back later.