cell phone tower/EMI on the f2

[fishguy]

I have the fisher F2 just got it about a week ago and I love it. I recently was out detecting at a park that I have been to before and it weant crazy and seems to do it alot certain times a day. My parents live about 15 miles away and I also detect there never had that issue. Now I am wondering could the cell tower thats about 250 yards away from my house cause this and How far from it is far enough away from it. Also there is a huge factory near the park Elliot company make turbines and stuff so I would assume alot of electronic running. would EMI reach that far, is it bad for my detector, and is there anything I can do to assist shielding it?

 

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[steve1357]

It's not bad, and nothing to do about it except turn your sensitivity down or use a smaller coil (antenna) if you have one.

I did an air test on my F2 for all five sensitivity settings, you might be surprised that cranked wide open isn't absolutely necessary. (I posted them in another thread)

It's a hot detector.

edit: from my earlier post

Used a 1994 clad quarter and the 8" stock coil.

Solid signal and accurate VDI reading

Sensitivity 1=5"
Sensitivity 2=5.5"
Sensitivity 3=7"
Sensitivity 4=8"
Sensitivity 5=8.5"

 

[DizzyDigger]

I have the fisher F2 just got it about a week ago and I love it. I recently was out
detecting at a park that I have been to before and it went crazy and seems to do it a lot at certain times a day.
My parents live about 15 miles away and I also detect there never had that issue. Now I am wondering could
the cell tower that's about 250 yards away from my house cause this and How far from it is far enough away from it.

Cell tower antennas are quite narrow beamed, and very directional. and typically operate at frequencies from
900Mhz all the way up 2.4GHz (and beyond). They are also frequently tested for emissions, and have to meet
some pretty strict standards for spurious emissions (radiated RF), or the FCC will fine them and shut them down
if they don't immediately correct it.

I can not find any data on how Fisher shields their internal components in the control box, nor do I
know the "clock freq" of any processors. If you were in the middle of a radiated field, and that radiated
frequency was at or near the same operating freq. of the processor, then it is possible that
RFI is entering the control box and effecting the machine, but then it would likely malfunction
completely and all functions would be effected. (Odds of this being a real issue are about
1/10,000,000).

Are you in the direct path of one of the antennas? This is doubtful since there is a park there, but I guess
it could happen. Reality is though, that at that distance you are dealing with the electrical field (far field) of that
transmitter, and with your detector operating at a very low 5.9 kHz, with a coil that transmits and receives a
magnetic (near field) signal.

Also there is a huge factory near the park Elliot company make turbines and stuff so I would assume
a lot of electronic running.

You betchya, and turbines can make one hellofa lot of RF noise. Truth is though, that if there was a
field radiating from the factory and strong enough to effect your detector, it would also likely be obliterating
computer screens and definitely having an effect on other computer operated equipment in the factory.

Those turbines (and any equipment being used in their manufacture) is required to meet some
challenging FCC requirements on emissions and susceptibility (ie: if they are radiating any EMI,
and also if EMI effects the machines/turbines functions), and they maintain records of this at
the company.

Would EMI reach that far, is it bad for my detector, and is there anything I
can do to assist shielding it?

In a word. No, No and ...maybe. You would have to be very close (< 10m) from that building
to even possibly pick up any magnetic field. It certainly shouldn't damage your machine.

Suggestions: Reduce your Sensitivity Setting when you encounter it. Next, make sure your
coil cable connections are snug, as a lose connection can cause issues as it becomes an
"antenna" all on it's own.

My best guess is that the park you are hunting in has been "filled", meaning that the soil
has been renovated. Much of the soil just under the grass may be from a source that was
foreign...ie: it was trucked in. I've often found that soil to be "hot" in the sense that the
detector has a difficult time trying to ground balance, and I'd get hot rock signals
up the kazoo. In that case I would either drop the sensitivity down to a setting where
the machine ran quietly, or I would go find another place to hunt.

So, make sure you are properly ground balanced for the soil conditions you are in, and
if you begin getting those "hot rock" signals, try and reduce the sensitivity a bit and see
if it clears up.

My two centavos worth...http://i292.photobucket.com/albums/mm24/schnickelfritzie/twocents-1.gif

 

[Sandman]

Electiical Interference

They won't hurt the detector and only affect how stable it runs. Even $$$ MD's will suffer.

 

[crazy4coins]

Hey fishguy!
I also own the f2, and the day I got it I went outside to test it in my backyard. Then I hit a point where my detector just went crazy. I thought "oh geez, I got a lemon" but then I remembered that there were power cables buried underground. They can really be a pain, because you obviously can't see them, therefore, you can never rule them out of the situation. Also, AC units can drive detectors crazy, so that could also be behind the problem. I'm not entirely sure about the factories and such, but if you run into a lot of EMI, your best bet is to turn down your sensitivity and search an area within the hunting site that has less EMI.
I hope this helps!
Crazy4coins

 

[DizzyDigger]

I am sure that Fisher (and other manufacturers) test their products to
certain standards as required by the FCC (and dozens of other governing
bodies). Will take a bit of research, but it would be interesting to know just
what specifications they have to meet. Might take a couple phone calls to
old friends, but this is worth checking into.

I'll post an update once I get the info.

 

[steve1357]

An old thread

http://www.detectingequipment.com/index.php?id=1418

Abt FCC and regs