F75 Target Seperation??

[BamaBill]

I just started hunting with the F75 and one of the things I'm noticing about my machine is that if there are several targets under the coil and I'm hunting in all metal, it blanks out the VDI and there isn't any tonal seperation, even though its a mix of iron and a good target in my test garden. The only way I get decent seperation with the VDI and tones is to hunt with 0 disc and in JE mode. Does this sound normal?

 

[Tom_in_CA]

If you're hunting in "all-metal", but have an option on your machine of having some sort of tone-id or VDI, then it's not true "all-metal". True all-metal would be where everything has the same sound (albeit of different intensities, depending on depth and size). If you're trying to look at tone IDs and VDI, then you are, in fact, using discrimination. In that case, yes, you are subject to the laws of masking.

Different machines handle target separation and averaging differently. Some better than others.

 

[thompy]

Bill what type of swing speed are you using

 

[BamaBill]

Thompy, I tried switching it up, swinging fast and swinging slow. I thought the reason that all metal would work so well on this machine was the VDI numbers. If VDI and tone are not workable options in all metal, then I might as well go back to using a tone only machine. Some of the experiments I've been running in my yard are teaching me just how much of problem masking is and I gotta tell ya, if you think your relic hunting site is hunted out, think again. The only way you'll ever come close to calling a site hunted out, is to spend a couple years pulling everything out in the top couple of inches and then re-detect the next couple of inches and pull out everything, until you've got it all.

 

[BamaBill]

Q: By saying you couldn't get tonal separation, did you mean that the multiple targets under your coil resulted in one sizable signal in the all metal mode? If so, did you try detuning the signal just slightly (using the pull trigger) to enhance the signal definition between targets (same as you do when detuning in pinpointing)?

A: Jim, yes the multiple targets only gave one response. No, I didn’t try detuning, but that is certainly a good suggestion and I’ll give it a try.

Without knowing how many targets are grouped together under your coil, and how much separation between them, it's not easy to assess the units performance.

A: There are 3 nails and a CW bullet in a space that’s about 3.5” inches across and they’re 6.5” deep.

The reason being that you mentioned the VDI "blanking out"; when it did so, did you also get the overload "whine" (or whatever you want to call it).

A: Nope, no overload whine, but the signal is loud.

One suggestion, consider the smaller coil. As good as the stock coil performs, I believe the smaller coil will do better.

A: I’ll give it a try, but on a CW site, switching to the smaller coil isn’t always practical and might not work well anyway. Most targets are in the 7-8” range and that layer can be quite junky, with a lot of iron nails and scrap. But, on the off chance that the small coil will get 8”, I’m willing to give it a try.

 

[Tom_in_CA]

BamaBill, you say: " If VDI and tone are not workable options in all metal, then I might as well go back to using a tone only machine." It's not that they're not "workable options" or "don't work", etc... it's just that they do not do as some people think they can do. A lot of people have the mistaken notion that they can get the best of both worlds, since they have an all-metal background, with a VDI or tone "front cover" to their all-metal. For example, some have thought that they could get all-metal DEPTH (which goes deeper than disc), yet retain TDI, tone, etc... and therefore effectively be getting the benefits of disc, while acheiving all-metal depths. Like, to know the TDI of the deeeepest whispers, just because their machine is showing them a TDI readout with the background of all-metal.

It doesn't work that way. You will still have all the limitation inherent with disc, even though you have all your screen or all your TDI's opened up, or any other such hybrid of the two. Inherent limitations like masking, depth limitations, etc.. That's not to say it's a BAD thing to run a hybrid like that. In fact, it's a lot of fun, since it nets you possible information that nulls alone might not tell you about the target mix your swinging over.

Hope that makes sense.

 

[BamaBill]

Tom, I think I understand what you're saying. I'm saying that in essence I'm hoping that in an iron infested area, that has a few keepers mixed in, I can run in all metal to get good depth and max stability, while watching the TDI as it registers iron and occasionally spikes to indicate the presence of a good target. You see, with the MXT I'm used to having a mixed all metal and disc signal (relic mode) that if shallow I can get a read on VDI and a two tone seperation, but if a little deep I can still rely on a momentary high signal breakthru, while its grunting on iron, to indicate the presence of a non-ferrous target mixed in. What I guess I was trying to do, was get a similiar setup going with the F75. I've had few other helpful souls make some suggestions I need to try and then I'll post my results in a few days. What I really appreciate is the outpouring of support and heartfelt advice as I learn to tame the beast (as it were).

 

[Tom_in_CA]

B-Bill, Oh, I stand corrected then. If you understand all that, then I guess I just didn't understand the question, as it applies specifically to the F75.

I misunderstood your original question to mean, that you thought that you could see through nails, because you were using a hybrid all-metal/disc. program. As far fetched as that seems, people have acutally reasoned that they should be able to do things like that

 

[liquid1]

Bill try this..Swing Fast..and furious and get back to us..I find that the F75 loves a fast swing in all metal motion and it will swap targets so fast its hard to see the screen numbers..so it looks like its Blank, Unless your saying it locks up on a Blank screen then you might have a problem with it...
Try this,Go in to all metal motion get a good Manual GB , go into audio set to 9,set treshold 0 to -3 tinker with the sense.you should hear a zip,zip on a good target, in Iron it will be a Deeper Zat Zat..This is my Beach wet salt setup..The VDI should work also..Kinda makes ya feel like cheating with this setup..Walk over target from all Directions..It will Go Deep so take a shovel..And I'm with ya on Digging some of the Bad Stuff to get to the Good Stuff..All Iron aint Bad, Alot of neat Horse,Western wagon stuff was specially Built by a Iron/Metal smith..I love finding 1 off Items..I'm no Pro and am new to Detecting..But I'm having a Blast with this machine..And I like to experiment with the options..james

 

[BamaBill]

Well, I went relic hunting for real today and ran into a whole new set of problems with the F75. I found out that in the disc modes I cannot hunt within 50 feet of another detector or my detector gets unstable. The only way to deal with it was to put it in all metal. This site is covered with a lot of iron at 3 to 4 inches down, but I was able to pick up an occasional good reading at 20 and above, but I was getting a lot of that blanking on the VDI with the monotone target signal. I didn't find much, a rivet and a few curious pieces of iron that registered higher, some foil. My hunting partner, with his MXT got about 5 or 6 good items (sharpes brass, melted lead, knapsack buckle, rivet, strap iron).

When I got far enough away I managed to switch into a disc mode setup, but this is going to be a real problem in the future if I can't use this machine near anybody else with a machine as I usually hunt with my son and lately with a hunting partner I've come to trust. If I have to keep hunting in all metal I'm going to have to sell this machine as it means something like 75% of its capability, and presumably what I paid for, is going to be useless. Why does this machine have to be so sensitive to stray EMI not under the coil? Is there not some kind of shielding they can use? I don't buy the argument about learning to use your machine when you can't get this thing to settle down, unless you're miles and miles from anywhere and hunting alone.

 

[BamaBill]

Let's talk about this for a minute. This problem you found with instability with other detector nearby; did it clear up for you when either he was out of range or when he shut his unit off?
A: It appeared to stop when he got out of range, however, I still haven’t ruled out it was something over at the house causing it. But, if it was something at the house, I’m still not happy, because I will probably encounter this again and it will reduce my range and capability with this machine.

When you used disc mode, was it JE or DE? That JE mode is highly unstable by comparison. Did the instability occur with the coil held say, about a foot above the ground and motionless? When you used the disc mode, did you use any iron disc, and if so, set to what level?
A: When I was using disc mode, it was the DE mode. I also tried JE and PF. Yes, it was unstable when I had the coil to ground or had the coil in the air. It’s the worst I’ve seen with this unit yet.

Bill, I presume you also tried the frequency adjust as well?
A: Yes, I did. I scrolled all the way through to F7 and nothing helped.

Last thing, what sens levels were you running, or did you try it at various levels with the same result?
A: I turned down the sensitivity to 45 and it seemed to help, but it was still popping and cracking, just a little less and not as loud. I still do not buy the argument that the lower sensitivity levels are just as good as the higher ones. With my MXT, a setting of 9 has definitely less depth than +3. I didn’t spend this kind of money to give up my depth advantage every time there’s a little interference. I might as well go back to a more stable unit, like the MXT if this is the kind of performance loss I’m going to experience on a regular basis. Relic sites are just not as remote as they used to be.

Back to your earlier post, I asked you how the MXT did on the same target group that was causing blanking on the 75.
A: I haven’t had a chance to run that test, but you can be sure I’m going to run it now.

I have not experienced any visual blanking, even over large iron targets (1" diameter X 6" long rusty iron bar) at shallow (4" or so) depth. Ever. I saw your post over on TD's forum about that and was it normal...and saw the reply that "yes" it was, but that you had "too many targets under the coil". That was a surprise to me. BTW, blanking...at what sens level?
A: It didn’t seem to matter what the sens level was, it responded the same way.

Sorry about the late response Jim, we were at my company picnic.

Bill

 

[BamaBill]

Thanks Jim, a lot to digest, but its the kind of well thought out help I need. I'll run the tests you suggest and get back to you.

Thanks Again,
Bill Walters

 

[thompy]

i have experainced, some vid blanking but tend to run in disc, unless prospecting or trying to find a new sites location, have had little problem with oher machines, the only one to cause it has been tesoro silver, which i believe runs 10 khz, if he was 30 ft or more no problems, the f-75 and t-2 sencetivity is not as linear as the whites, i had a lot more problems with cross talk with my whites QXT,S. since your buddy is running the mxt the khz are pretty close between the 2. sorry the f-75 isnt working out for you

 

[liquid1]

Jim, It sounds like you are pretty well adverse with the F75 and Mxt..And all your units..Great info....NOW you guys have me Glued to the screen on this topic..james