Which coil around power lines.

[7centsworth]

I hunted a sight saturday for relics and it was the worst place I have ever hunted for emi inteference. The place had a electric fence around the field and a power line right over the middle of it. I only had the 10.5 dd 7.5khz coil with me and man was it bad. I had to turn sensitivity down to 19 to get it to calm down . But there was know way i was leaving it at 19 in a field with civil war relics in it . The grass was tall and I bumped the sensitivity up to 23 and dealt with alot of it. I have the 10.5 coil the stock 9 inch coil and the 6 inch dd. So my question is which coil would be the best there? I found one of the best enfield bullets I have ever found there. Thanks for the help. Travis.

 

[mapper65]

My post may or may not help to answer your question but a few months back after about 7 trips to the same picnic grove in a local park I found 263 coins in this particular grove. The thing that still has me a little stumped is that the grove has power lines running right through the middle of it and most of the coins that I found were within 30' on either side of the power lines. I have attached a Google Earth photo of the location.

It has been the best single location that I've ever detected in producing 8 silver, 4 buffalos and 15 wheats with the remaining 250 coins being your typical pennies and other clad coins. The power lines are definitely active being that they feed power to a neighborhood just on the other side of the park. These are main lines which in one direction is the grove and neighborhood and in the other direction you can see the lines running through a cutout area of the woods that are easily in view for 3/4 of a mile.

I guess it may depend on what level of power that power lines supply and if they are using any kind of insulation as to what may be radiating off of them. Each day I did my typical setup of noise canceling and auto ground balance. I was using the 10.5" & 6" HF coils and at one point used the 6" MF coil for just a short period of time.

I believe that you are having this issue but so far I have not ran into any noise problems in any areas that I have detecting in.

Again, this may not answer you question but I guess it's input never the less.

 

[7centsworth]

Mine constantly beeps and chatters. I have ran into it before but not this bad. With the power line and eletric fence makes it really bad.

 

[Clad2Hunt]

Im hunting with a 9"MF next to the huge towers and a place my FTP wouldnt settle down. But when the wires get closer to the ground for house feeds I had to go down to a 6"HF and could run at 23 sens on 705. EMI can spoil a day so glad I carried a backup.

 

[Digger]

All metal detectors are susceptible to electrical interference. Simply put, the purpose of a metal detector is to detect a magnetic field. And electric lines produce magnetic fields. The more "sensitive" the detector, the higher the likelyhood that it may be effected by this interference. VFLEX in the X-TERRA circuitry has greatly reduced the amount of interference induced into the circuitry via the cable to the coil. (most detector cables act as an antennae for interference). When mine gets sputtering due to some sort of interference, the first thing I do is to perform a Noise Cancel. If I can't get it perfectly quiet, I lower the Sensitivity a couple clicks and do the Noise Cancel again. Go through this process until you get a combination that works for that site. Another suggestion I would offer is to hunt directly parallel to those power lines. I've found that running at a 45 degree angle to the lines is when I get the worst interference. Seems the more parallel I go, the quieter it is to hunt. Smaller coils will be less succeptible to outside interference. (the coil acts as an antennae, too) And when I'm hunting around power lines, cell towers, or any other source of RFI, I've found I can run my 3 kHz coil with higher sensitivity than the other two frequencies. Bottom line is........ if after trying the things I suggested, recognize that hunting with a lower (than desired) Sensitivity is still better than going home to mow the yard. JMHO HH Randy

 

[7centsworth]

I think the combunation of the power lines and fence are what make it so bad.

 

[Donut]

There is definitely a electrical field under high power transmission lines. I was once driving a 1ton pickup truck carrying four large industrial wire basket stacked two high in the bed and I stopped on the interstate to secure the load and I accidentally stopped under the lines and jumped out of the truck and just garbed one of the baskets with my hand to help clime up and got one heck of a shock.

Doug

 

[TURNMASTER]

Bottom line is........ if after trying the things I suggested, recognize that hunting with a lower (than desired) Sensitivity is still better than going home to mow the yard. JMHO HH Randy... Agreed

Just a though,t but I was having problems and it helped to get rid of the coil cover. I think there were still a few particles of dirt still in there and it helped to set up a bad resonance. I was hunting fairly near to high tension lines. I seemed to be ok with the cover. I doubt I was able to run the sense any higher than 22 to 25 though. Give it a try next time and let us know.

Jeff

 

[Mtnmn]

I have three different size coils and the 6" coil works the best directly under high tension lines when used along with noise cancelling, probably for the reasons Digger stated. My XT-70 was never setup very sensitive at the factory and while it has definitely cost me some depth, it has also made detecting around and under high tension lines not much of a problem. Which in turn has allowed me to find a lot of coins where the EMI was probably too much for the average detector, helping even things out a little...

 

[Furious T]

If you are working in an area of intense interference, sensitivity between 19 and 23 doesn't sound too bad...it may not be as much as you would like, but if you do the noise cancelling procedures outline by Digger, you will be able to run sensitivity as high or higher than some other "high end" machines would cope with. JMHO

 

[7centsworth]

I noise cancelled about 15 times during my hunt. It never seemed to help much. Every spot I have ever hunted it helped ,but this one having two interferences is killing me. I will not get frustraed though I am going to hunt it anyway I can. I know it has more relics on it. I managed to find a perfect enfield drop almost under the power line. And it has been hunted before. I had to really listen to figure out the electric noise and a good signal. Thanks for all the help.

 

[Old Katz]

I thought there was a noise cancellation feature on the 705 like the 505 .
Katz

 

[7centsworth]

There is.

 

[TURNMASTER]

High tension lines generate a TON of EMI that some machines can not cope with.

 

[Old Katz]

Hummmmm. Sounds like a challenge for MindLab. I wonder if they are up to it?
Katz