Is the F75 LTD really "useless" in the city?

[Mojave]

I've been interested in this detector, primarily because of the depth capabilities, but I've read a couple of reports where people simply couldn't hunt certain sites because of EMI interference.

I do a lot of relic hunting but I don't want to give up my ability to hunt coins in the city. If there's an electrical tower nearby, I don't want to have to skip a site. My Minelab SE does well against EMI, but the slow recovery speed has caused me to look at the F75.

 

[markg]

I've had EMI problems, but all could be over come. Usually reducing sensitivity works. Just because the sensitivity is set on 50 doesn't mean it's not deep.

 

[marcomo]

You're really struggling with this decision, aren't you Mojave?

I can tell you I've never yet had EMI so bad that the detector was not effective. But, in fairness, I've only had the detector about 3 months so I may still run into one of those spots.

Even at low sensitivity, this detector is excellent and deep.

I never had the original F75, but I'm guessing that somehow they have done a better job of shielding the LTD from interference.

I've tried turning the cellphone in my pocket completely off while hunting in several places to test it and it has made no difference interference-wise.

 

[tvr]

I've been near several potential sources of interference such as over head and underground power lines, including the high voltage towers, cell phone towers and play grounds in the middle on fairly dense housing. Most are not problems at all.

I have had two places, out of about 15 or 16 locations I've taken the LTD to, that have given me problems. Changing the frequency did not help much for me at these two locations. Reducing sensitivity until quiet allowed hunting at both places.

I was pleased with what I was finding with the reduced sensitivity. I could readily tell that one specific transformer out of a bank of four was radiating at one site (school yard) and one power distribution box out of two at the other site (ball field) was an issue. The further away from the interfering source, the higher I could run the sensitivity.

One of the sites, when I first took the LTD there, I reduced sensitivity to 20 and it still squawked so much that I got the Tejon out of the car to hunt the sidewalk area near the transformer. I posted that a few months back. I have since gone back with the LTD and dug some nice clad counts along the edge of the same part of the sidewalk I hit pretty well with the Tejon. The difference was I dropped the sensitivity even more until it quieted down on the second trip.

Have had recommendations to send the detector in to get checked. I think I will. But I would not recommend letting the reports of interference shy you away from the LTD or from what ever version of the F75 with the boost mode that comes out next.

Most reports of turn around time I've seen for sending the detector in have been about on the order of a week, including the shipping times; not bad at all.
tvr

 

[gates21]

If it makes you feel better I was just able to turn my ltd sensitivity up to 86 right next to my computer with the tv on about 10 feet away and virtually silent.
Even with the sens at 50 it still has great performance.

 

[Chris(SoCenWI)]

And a Minelab XS and can say they are pretty similarly affected by EMI, at least the most common type caused by power lines. I do a lot of in town terrace hunting; usually have power lines over head and usually have to turn the sens down, sometimes way down. If I have to do it with the explorer have to do it with the F75. And yes depth does suffer when this happens, not sure if any detector out there is better.

Chris

 

[Cal_Cobra]

EMI was a HUGE concern for me when considering to purchase the LTD or not as I do a LOT of my hunting in the city (Oakland, San Francisco, etc) where heavy EMI has zonked out several machines in the past (F70, F5, etc), as well as friends who had the legacy F75. After the initial reports came out, there were some positive reports from users that had hunted with both the legacy and LTD 75, and there seemed to be a positive trend towards the F75 handling EMI better then the legacy F75. I've also found this to be the case, and have only found a couple of spots where EMI was a problem (and oddly they weren't in the big city either), and only one that rendered the F75 LTD unusable.

Personally I say go for it, I believe you'll be quite pleased with the LTD

 

[Mojave]

Thanks for the responses.

I guess my concern is that, if I run into an area that has a ton of interference, I'll have to crank the sensitivity *way* down to get the detector to be stable enough. Even if I use boost mode, with a greatly reduced sensitivity, it's doubtful it can beat an E-trac at depth, and I wouldn't suspect that the E-trac would have a problem dealing with the EMI.

Don't get me wrong, the F75 LTD seems like an amazing detector, but this one potential drawback may be the deal breaker.

Someone sent me this video. I don't think an explanation is needed.

http://www.youtube.com/watch?v=8zJfOtTWj1A

To be fair, this is the original F75 at 0 discrim, 60 sensitivity, not the LTD.

 

[gates21]

You have to remember that running the F75 with under 6 disc or over 20 (I think) puts it into a higher gain mode that does cause some instability. Disc at 6 on an F75 is equal to disc'ing out small iron. As soon as you put it in 6-19 disc, it becomes much more stable

 

[Mojave]

Doesn't that negate the added depth that this machine apparently gives though?

 

[christopher-ohio]

you may love it and not want to go back to the heavy E-Trac or the opposite and you can just sell it-no big deal...HH and good luck with your decision

 

[Scully]

I can get both my F75's (orig & LTD) to do that in certain places. Or that machine may have needed to be rebooted. Every time a sensitive machine comes out, people seem to complain about "interference". All sensitive machines, if not tuned properly, will be noisey! If its chattering, you dont have it set properly. Even at a Sens of 10, the machines are hot. With the F75, to really make it work to your advantage, let the machine tell you where to set everything. Turn the Sens down until the machine is stable, no matter what that number is. Switch freqeuncies. Try running in All Metal (that really quiets the machine down). You might be surprised.

 

[go-rebels]

And a Minelab XS and can say they are pretty similarly affected by EMI, at least the most common type caused by power lines. I do a lot of in town terrace hunting; usually have power lines over head and usually have to turn the sens down, sometimes way down. If I have to do it with the explorer have to do it with the F75. And yes depth does suffer when this happens, not sure if any detector out there is better.

Chris

My Minelab Explorer II was more negatively affected by EMI compared to my original F75, and my F75 LTD is slightly improved with regard to EMI compared to my original F75. Regarding the video posted above, who knows what the settings were on that unit? Regardless, I could make by Explorer II chatter away in a similar fashion when I set sensitivity to manual and ran it up to 29-30.

 

[Charlie P. (NY)]

I've had the F75 (original) since May of 2007 and I have never been shut out of a site. The worst EMI I have had turned out to be an "invisible" dog fence that bugged me out when I got within about 10 ft of it. There do seem to be some spots where "chatter" is a real problem. Usually just tuning down the sensitivity and hopping a few frequency points solves it. It's a sensitive machine, no doubt about it, but that is why it finds faint targets.

Some sites are just electrically more noisy than others. The trick is to ignore the falses and dig anything repeatable. I started with a Musky (no visual of any kind) and for depth that one needs a tight ground balance. So to be sure I'm on the hairy edge I set it slightly positive. That results in a signal at either end of the swing or as terrain changes. Point is, I guess I'm used to some background mumbling so I know I'm pushing the edge of the envelope.

PS - if you lift the coil the F75 goes knutz because it does pick up stray signals. Set the sensitivity (and all other settings) with the coil held close to the soil. It is not a machine for air-testing indoors. It is for detecting metal in the soil.

 

[jim tn]

I had a situation a week or so ago on a small field that I was hunting that on one side power lines were almost directly over head and would literally shut my LTD down for brief periods. At the time I was hunting with disc. 0, sen. 87 and bp mode. I moved the disc. up to 6 and left everything else the same and the LTD became very stable and quiet. I made about 3 or 4 swings and got a good dime reading, which just happened to be a Merc., at a true 5-6" deep. Yes, there may be a bit of depth loss moving from 0 to 6 disc., but as hard, clean and crisp as the dime was hit, a good bit more of depth was attainable and certainly not enough to negate the merits of the bp mode under such conditions. HH jim tn

 

[Low-Boy/LCPM]

THAT IS WHAT HAPPENS TO MY MACHINE WHEN EMI IS ABOUND I CAN'T EVEN FAST GRAB. BUT THAT DOES NOT HAPPEN A LOT JUST SOMETIMES BUT WHEN IT HAPPENS IT IS OVER.RESET, NEW BAT, LOWER SENS DOES NOT REALLY HELP.
BUT THE LTD IS SUCH A GREAT MACHINE IF YOUR MACHINE GOES CRAZY GRAB A BACKUP LIKE THE CZ3 OR CZ70..THE DESIGN OF THE LTD MAKES IT A SENSATIVE HUNTING MACHINE. YOU HAVE TO LEARN HOW TO HUNT WITH THIS MACHINE BECASUE IT SEES SO MUCH IN THE GROUND WHERE OTHER MACHINES MISS THAT AND WALK OVER MASKED TARGETS.

I WOULD BUY ANOTHER ONE BUT I AM WAITING TO SEE WHAT FISHER COMES OUT WITH IN THE NEXT YEAR OR TWO. I LOVE THE LTD AND NEVER USE MY F75 I WOULD ONLY USE IT IF THE LTD BROKE.

 

[Chris(SoCenWI)]

Although the explorer is more talkative I did find that when I turned either of them down enough to be stable enough to use, the depth of detection was very closely matched.

Chris.

 

[jmaryt]

hi low-boy!
in your experience,do you believe the f-75 ltd is QUIETER running over all,than the standard f-75?

thanks!
(h.h.!)
j.t.

 

[jamt225]

I've hunted city and rural with no problems except a sore back from digging. I just hate those gold items the F75 ltd keeps making noise on.

I'd recommend not getting an F75 ltd, as too many folks probably already have one, and why get something with so many problems?

Just saying. Good luck on your decision.

 

[Low-Boy/LCPM]

It is very quite and I can use 0 disc remember that what you hear is what is in the ground where other detectors don't see that. So you will get chatter but if you use 2F you will hear the iron and hear the good targets.