F5 EMI

I bought my F5 last year and I love it with the exception of what I've been told is EMI. I have never been able to run full gain on it anywhere and I have to run my threshold lower [-3 ]or lower to even be able to run my gain up past 75 and vice verse. I did contact Fisher after I first got it and was told it's normal and even read several forums and for the most part came to the conclusion it was the nature of the beast, like I said I love the detector but also don't feel I'm getting the most out of it and actually only use it for tot lots etc. due to this issue. I would like to know if it is normal and the nature of the beast or if their is something that can be remedied by sending it in. The closest video example I could find was the youtube link below. Thanks all who respond.
[www.youtube.com]

Do a search here and at FindMall using "Mike Hillis".........don't use the parentheses in the search box. Just enter the name. Use the advanced search feature hyperlink and select...exact phrase......and.....all dates
This should get you everything by the F5 guru.....Mike Hillis.

I notice your in your video that your test is on a block ledge of some sort. What kind of structure are you standing in? I use the F70 and when I am in town hunting yard I always have to have the threshold in a negative setting. Sometimes in very large lots I can run it at -1 if I am away from all buildings and power lines but closer to them I often run very close to the default settings. When I first got the machine I always felt like I couldn't get enough depth with the default settings so I would crank it to just barely past insanity and my performance was less than I hoped for. On the flip side, when I was out in the rural settings I could run it fully wide open and keep up with the big boys. Sometime after I finally got good enough to know when I had a deep silver dime before digging a thought finally occurred to me to mess around with the setting and see how that changed the tone and ID and how low I could take the settings before losing the signal. Surprisingly to me I could go below the default and still get a great signal that would cause me to dig the target. After that I started using settings that were near default and low and behold the detector started producing better than I dreamed. Apparently confidence makes all the difference. I wouldn't be surprised if your F5 has the same issue as mine did.......lack of confidence.

LGC, your post is spot on! Learning the hows/whys and setting for conditions is moreso the key instead of what particular detector one is using.

limegoldconvertible68 --

I also have an F70, and have been trying to learn it (I have about 30-40 hours on it), and in your post above, you said:

"Sometimes in very large lots I can run it at -1 if I am away from all buildings and power lines but closer to them I often run very close to the default settings. When I first got the machine I always felt like I couldn't get enough depth with the default settings so I would crank it to just barely past insanity and my performance was less than I hoped for. On the flip side, when I was out in the rural settings I could run it fully wide open and keep up with the big boys."

You just summed up my experience exactly, with the above quote. That thing is noisy/chattery BIG time in town. Rural? I can crank it, no problem. But, like you, I have feared that "cranking it down" in town to where it's a bit quieter/more manageable, would mean losing deeper targets. However, the next thing you said was very encouraging:

"Sometime after I finally got good enough to know when I had a deep silver dime before digging a thought finally occurred to me to mess around with the setting and see how that changed the tone and ID and how low I could take the settings before losing the signal. Surprisingly to me I could go below the default and still get a great signal that would cause me to dig the target. After that I started using settings that were near default and low and behold the detector started producing better than I dreamed."

I have been moving in this direction -- setting up the machine to be "manageable" depending upon local conditions, and just trusting that it will still perform well. Your statement above encourages me that this indeed will be the case.

So, to bring this all the way back around -- Coyote65, I think your F5 is similar, very sensitive, but as a consequence, chattery and noisy -- especially in town. The good news seems to be that cranking these things down until they are "manageable" to your ears and brain, does not make them run so "cold" that you will miss a bunch of stuff. I know this is helpful information for me to think about and begin to apply to my own hunting; maybe it will be helpful to you, too.

Steve

The video in the link above is not mine but rather just one I found that resembles the way mine acts. Mine has EMI issues no matter where I hunt, be it an urban park where I'm sure there is some EMI or in the middle of the woods where I'm sure there should be no EMI. I've ran it for almost a year now and have read most all of Mike Hillis posts "even compiled a list" from them, not as many here but at another forum and why I came to the conclusion it was the nature of the beast, but I had read where a couple had mentioned they sent theirs in for repair and they came back stable so after reading this I was confused again on whether or not it is normal operation. Yes my confidence is shaky at best on my F5 and why I only tot lot hunt with it. I will say neither of my other detectors behave in this manor, maybe the F5 is just not the detector for me, like I mentioned I love the looks of it, I really enjoy the combination of analog and digital controls, the display is large enough these older eyes can read it and it is just a tad coil heavy but for the most a joy to swing. Below is a Tips list for the F5 from Mike Hillis comments:

Set the unit in DIsc mode, d4 (4 tone mode), Gain on 80, Theshold on -9, and Max out your Discrimination. Only recover repeatable high tones. All you'll be hunting is silver and copper and clad dimes/quarters/ etc. Just get use to doing that for awhile. Your treasure to trash ratio will immediately improve. Then when you are comfortable with both the digging and high tone targets, notch in the Nickel range and hunt that way for awhile until you learn that range of targets. Then as you feel comfortable, add in another segment, like the zinc segment. It has has a different tone and you'll be looking at a completely new range of targets.

It wont take long to learn whats good and whats bad, your recovery method will improve and you'll grow more comfortable with the unit. Then you can raise the threshold setting up to 0 and spend time on the deeper and smaller targets.

Most of all, don't be afraid to limit your audio input with the disc and/or notch settings. Keep the audio feed to your ears understandable. When the trash gets too heavy, raise your disc or notch it out so that you can still hunt the good stuff.

When the F5 freaks out and with that double beep sound followed by the two hash marks in the display or nothing in the display, that's a overload signal. When you get one of those you need to raise the coil higher and resweep.
Overloads are caused by surface targets that saturate the recieve circuits or large rusty iron objects targets thats leeched the ground with rust. Rather than just going quiet, the F5 gives a different sound so that you know you are overloaded and can act appropriatly.

Regarding tones that are strong but don't registar a number....at this point in the game you need to ignore those.

The deep grunt tones will be iron objects, usually heavily oxidized. Depending on where you have your discrimination set at, these will either repeat or, as you are discovering, will hit once and then go quiet as the discriminator kicks in and silences them.

Regarding running the Threshold in the positive range that 30 + signal....if you have a good clean, repeatable audio, you had a good target that you lost while trying to recover it. Remember that with postive threshold numbers, the F5 will pickup very small targets that could be hard to locate if you are expecting to see a nickel or tab, and in reality are chasing a tiny rivet. A good Pin Pointer
is very useful in this scenaro.

Think of Gain as a magnifier. The higher you raise it, the more it magnifies target signals, making them appear larger.
The Threshold is split into two features:
From settings of -9 to 0, think of the threshold control as a door. The door is shut at -9 and the door is fully open at 0.
From settings of +1 to +9, think of the threshold control as a volume control that makes all the signals that got into the wide open door louder and easier to hear.
Thats kind of an over simplified description of the controls but pretty accurate nonetheless.
When setting up the detector, think, "how big do I want the signal to be (GAIN) and, how large of a signal do I want coming through the door (THRESHOLD)" and if you have the door wide open (threshold at 0), then how loud do I want the tiniest signals (threshold above 0)
Then of course, the actual site conditions laugh at you and say, "sorry buddy, but you're going to have to make the signals smaller or close the door a little." And then the two of you work out the best compromise for the targets you are after.

The combination of the three features give the user a lot of control over the detector. Add the 4 different tone modes to it and the F5 has a lot going on with the audio.

If it was just a non-repeatable chirp, that would most likely be an iron false, or, if your settings are too high for the site, EMI.

Starting out: gain at 70 threshold at -9. Disc. at min. Run d2 or d3 mode until ya get the hang of it. Metal mode: gain at 30-35,threshold at +1 / +2. If you want high gain, lower your threshold to 0 or into the negative numbers. High trash area: gain at 70, threshold at -9. Notch out iron, foil, tabs, and .50 cent. Running hot: gain at 90,threshold at 0. Or gain at 50, threshold at +5. Machine may chatter when still but stablizes when swung. This is for greatest depth in clean ground (low mineralization). Use a 1 - 2 second to 4 ft swing speed.

3-4 Tones, Discrimination 6, Sensativity/Gain 85, Threshold 0, = hot setup for normal objects..
3-4 Tones thresh at +5 and and the gain at 60 and disc wide open = hot setup for small objects.

The F5 pinpoints right in the open area just in front of the rod. If it will help you, take a golf ball and roll it back and forth in the open area of the coil and you'll see the coil center a little clearer. Then take a piece of chalk or something and mark that center circle if you need to. That will be your pinpoint area.

Also, on shallow targets, you can pinpoint with just the toe of the coil. Don't use the pinpoint mode. Just leave it in your hunt mode and wiggle the coil sligthly back and forth as you pull the coil back and when you loose the signal the target will be just on the rim of the transmit coil (outer loop).

Thanks for the reply's,
Coyote65.

There are six methods of EMI mitigation on the F5:

First is the Frequency switch. Set your threshold to a positive number, run the gain up until it starts to chatter and then switch frequencies until you find the best one, then reset your controls where you'd rather have them.

Second is the Threshold control. -9 to +9, zero inclusive. Pick your Threshold setting and then change the Gain to support it, or pick your Gain setting and change the Threshold setting to support it.

Third is the staying at the "still coil" settings.
With the coil held motionless, adjust your gain and threshold settings for stability.

Fourth is staying at the "in motion" coil settings. With the coil in motion over the ground, set your gain and threshold settings for stability. You can usually run higher gain setting with the coil in motion than you can with the coil held motionless. However, it will chatter when the coil is held still.

Fifth is raising the disc setting up into the foil range. This will often kill some of the EMI responses.

there is a sixth if you can call it that. That would be turning your Threshold knob full forward hard into the stop. Sometimes that will put you into a reduced performance state that will eliminate the smallest signals. I don't recommend this, and it is inconsistant but it does work.

Always want to do the first method. The others depend on ground conditions and the targets you are after.

HH
Mike

Thanks Mike I will save the above notes with my others and try those techniques out, like I said I really like the detector it's my confidence in it due to the EMI, I have never found a spot where I can run the gain much past 65-70 with the threshold at 0 or above. I can run my gain at 75-80 but in order to do so I have to back my threshold down to between -3 to -5. On the flip side I can back my gain down to 50 or below and that allows me to run my threshold up in the positive range +1 or above, I just feel when the EMI or chatter creeps in I'm not obtaining the full potential of the detector add to that the confidence factor and although I love the aesthetics of the detector I'm not 100% confident in it. I don't mean to sound as though I am trying to hunt wide open, just want to know I'm not missing things due to having to decrease the performance of it. I'm well aware of the conditions of a site dictating to the detector as to the settings you can use, but I did think out in the woods away from electrical interference you would be able to run the gain at least 85 with the threshold of 0 or +1 with stability but I've not been able to. So my main question was I guess this is just the nature of the detector and while EMI does play a part in the urban parks out away from any EMI issues the detector can be bumped up slightly, it still exhibits instability "chatty" and nothing is wrong but just the way things are.

Thanks for the tips,
Coyote65.

Coyote65 --

You sound like you've tried about everything, but I'll add one more thing. You mentioned in your initial post about a noisy, chatty detector that you say you "have been told is EMI." It is at least POSSIBLE that it's not. A tip I got from someone and try to keep in mind is that to find out what is causing your "chattiness," you need to determine if it's EMI, OR something in the ground (hot/mineralized soil, or just a tremendous number of small targets). You probably already know this, but, the rule of thumb is -- hold your coil motionless about a foot off the ground. If it is chattering, it's most likely EMI (or I guess it could be a coil issue, too). If not, but then it chatters when you swing it over the ground (as if you were hunting), then it's something with your ground, in which case ground balance issues may come into play, or you just may have a jillion and one small targets in the soil.

Are you in an area known to be highly-mineralized? Have you ever tried another coil to see if you might be able to rule out it being a coil issue (loose wire, bad connector, etc.)? Further, along the lines of the coil -- I'm not sure what coil you are using, but the DD coils are definitely "quieter" than concentrics; at least on my F70, I can run my machine MUCH hotter (and still be MUCH quieter) with the 5" DD coil, versus the stock 10" elliptical concentric.

I doubt this tells you anything you don't already know, but I thought I'd throw it out there.

Steve



Edited 1 time(s). Last edit at 03/02/2011 08:09PM by steveg.

EMI is more widespread than it used to be and metal detectors are getting more high powered than they used to be. Electrical interference is really becoming an issue. A threshold setting of 0 (zero) on the F5 really is "wide open". It is going to be rare that you can hunt with it wide open with high gain settings. However, the F5 (like it's younger brother the Omega) can use the ground signal to help mitigate or cancel out EMI responses IF you have enough ground signal.

This is what allows higher gain combinations to be used. With the coil held still, set the threshold on 0 (zero) and then raise your gain to just below the instablity point. Then with the coil in motion over the ground, begin increasing the gain settings until you reach the new instability point then back it down to where it's stable. Those are your max settings for that location. As soon as the coil motion is stopped it will chatter like a banchee but once it is back in motion over the ground it will be quiet. Remember its the ground minerals that are being used to cancel the EMI. If the site's ground mineral are low you may not be able to use this approach.

Maybe that will help.
HH
Mike

Good info and thanks for the reply's, I haven't tried another coil I use the stock elliptical concentric coil. Rather than switch coils I have a Tesoro with the 5.75 widescan coil for tight spots and hunting in around fences, boulevards etc.
I live and hunt mainly in central Illinois and wouldn't call the ground hot but will keep a closer eye on it and the erratic behavior and see if I can figure out any correlation and apply the tips I've received here to gain a better grasp on exactly what's going on.

Thanks all the tips and reply's.
Coyote65.