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Thread: Estimating Optimum Recovery Delay Settings

  1. #1
    Super Moderator deolslyfox's Avatar
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    Estimating Optimum Recovery Delay Settings

    There has been some discussion on the forum since the release of V3 regarding Recovery Delay and how to set it .... I have set up a chart showing RD time settings for four (4) coil sizes - 4", 6", 9.5" and 10", deployed at sweep speeds ranging from .5 ft/sec to 5.0 ft/sec. The "average detectorist" swings somewhere between 1.5 ft/sec and 2.5 ft/sec. At 2.0 ft/sec it will take 2 seconds to swing a 4' arc in one direction.

    First off, definitions: Recovery Delay settings are just as the name implies - the delay time that you are imposing on Spectra before it can process a second target after the first target has been processed. Another term would be Signal Processing Delay, or how long Spectra has to process the first target, and then be ready to process a second target. When I "explain" this time, I like to use the analogy that a target is processed in four steps .... (1) It is acquired (2) target data is calculated (3) target data is displayed (4) target is released and housekeeping done in preparation for the next target. Steps 1 - 4, added together = Recovery Delay.

    Lower numbers = SHORTER delay. Higher numbers = LONGER delay.

    Optimized Recovery Delay is a function of Sweep Speed, Ground Filter, Mineralization, Coil Size and to some degree, RXG and Disc Sensitivities.

    The premise that the attached chart is founded upon is that (1) the coil can't see anything before or after it is over the target (discounting edge effect for purposes of this discussion) and (2) a full coil width's separation will minimize masking. You may find that you can actually reduce your delay times a bit from the settings in the table. They are given a 5% margin to address edge effect. I used the middle of the road 7.5Hz filter.

    Faster RDs are best deployed in high trash areas. Slower RDs will provide more depth, up to the point that the coil is no longer over the target. Increasing / decreasing RD around the "recommended chart setting" will not add or subtract inches from your target depth, unless of course you adjust "too far" in one direction or the other. EG: A RD = 0 will make a quarter "chattery" at about 3", so that's "too short".

    Coil size. Just want to touch on this .... A 4" coil (4X6"DD shooter) will pass over a quarter in less time then a 10" coil (10"DD) if both are moved at the same sweep speed. Thus, it has been my suggestion that if one is making a significant change in coil size, it may be worthwhile to adjust the Recovery Delay accordingly.

    The chart is purely mathematical. I have sampled the data using all four coil sizes and varying sweep speeds and the performance matches the numbers. Please note that the sweep speeds are "Mississippi's", they are not timed with a laser and the coil wasn't moved by a highly consistent mechanical arm.

    The quickest way to arrive at your "optimum" RD (IMHO) would be to place a two coins, one coil's width apart and swing the coil at your speed until you got two hits from the unit. If you know your sweep speed (and most people think they are sweeping slower then they really are) then the chart will "get you in the ballpark" and minimize your tweaking time. It will also provide a "sanity check" for your program settings as you develop them, or perhaps help you understand other people's program settings.

    To estimate your sweep speed, lay off a line 4 feet long. Stand in the middle and sweep your coil from end to end, counting "Mississippi's". A 2 ft/sec sweep speed should take you 2 seconds to cover that 4 feet in one direction. I have seen many a surprised detectorist when they discovered that their sweep was closer to 4 ft/sec !!!

    Hope this is helpful .... Da FoX

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    Last edited by deolslyfox; 06-16-2010 at 12:16 PM.
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    Is Fox great or what!!

    Between you, Fox, and Robert and Carl, the rest of us are really blessed to have you guys helping us out, especially someone like me that is getting back into MD after 25+ years! Thanks everyone with the great posts (I know I'm missing several people who also contribute [like Nitro], can't remember them all, but you all are wonderful).

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    Junior Member pointer80's Avatar
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    Hey fox, Very,very helpfull information!!!!! I am going to start doing some testing and using your chart for reference. Now I'm just wondering when you and rob and jack write a book is that going to be paperback or hard cover, color or black and white. thanks again pointer80

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    Thanks Fox My bookmarks are sure filling up fast
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    just thinking out loud fox,, we say a rd of 120 gives the spectra more time to analyze a target versus an rd of 45. my question is doesnt the computer do this instantly . i mean like millisecs.. another words the lower the setting you can use without hinderance from masking from the next target be the best setting. i guess what im saying is the machine does it that fast no matter what. we, say lower rd for trashy area when in actually we should run this whenever theres numerous targets good or bad close together. what i guess im asking is does the machine itself give you any better info by givin it more time.. sounds stupid but just wondering

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    Guru Evan/tn's Avatar
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    Nice info fox I knew i had my RD set to fast and might be losing some depth and i think i should slow my swing speed down some
    Thanx for all youv'e done
    **********Swinging Whites since 1978**********

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    Super Moderator deolslyfox's Avatar
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    Quote Originally Posted by johno View Post
    just thinking out loud fox,, we say a rd of 120 gives the spectra more time to analyze a target versus an rd of 45. my question is doesnt the computer do this instantly . i mean like millisecs.. another words the lower the setting you can use without hinderance from masking from the next target be the best setting. i guess what im saying is the machine does it that fast no matter what. we, say lower rd for trashy area when in actually we should run this whenever theres numerous targets good or bad close together. what i guess im asking is does the machine itself give you any better info by givin it more time.. sounds stupid but just wondering
    You are thinkin' good .... And yes, Spectra's processor does do things in milliseconds, but a millisecond is a long time .... Blink your eyes .... That is roughly 250 milliseconds. One quarter of a second ....

    Giving Spectra "all the time it needs" (but no more) is the right answer to your question (IMHO). It's like cookin' .... Too long in the oven and its burned. Too little time and its raw .... To my way of thinkin', "just right" is to give Spectra all the time that the coil is over the target, plus a little bit for edge effect, and a touch to process the data, display and do housekeeping.

    Now, lets talk about "Time on Target" (ToT) for a second .... (That's 1000 msec btw). A "normal" rate of coil movement is somewhere in the 2 ft/sec range. That's 24 inches per second. So, every 1000 milliseconds, your coil moves 24 inches. That equates to about 42 msec per linear inch of motion across a fixed point. (1000 msec / 24 inches = 42 ms/in)

    If the coil isn't OVER the target, or "just past it", the coil isn't sending any target data to the box for processing .... (well, duhhhh ... ). And yes, there may be some edge effect, but gimme a little slack .... I'm tryin' to keep this on-point and as simple as possible.

    So, if it takes a coil 42 msec/in to pass over a target at a swing speed of 2 ft/sec it will take 420 msec for the 10"DD to completely pass over a point. (42 ms/in * 10"). If we give Spectra a little "extra time" for cleanup (ToT post processing), then we've allowed for all the data to be gathered, processed, displayed and housekept. Let's say that adds a burden of 5%, (completely arbitrary), so now we're up to about 440 msec. If we give Spectra much more than that, we are just in "dead time". It has seen the target, processed it, displayed it, done its housekeeping, and is ready for the next target. Keepin' the processor tied up for 600, 700, 800 msec doesn't make any sense to me, and I can't see any depth loss if we follow these "rules". As long as you have given Spectra enough tiime to process all the data available from the coil AT YOUR COIL SWING RATE, and added a little "Kentucky windage" for housekeeping, you're there.

    And just to be clear - the SLOWER you sweep, the longer your coil is over the target, the longer Spectra is getting data, the SLOWER your RD (higher number) needs to be. Is there a "Maximum" delay ? Based on the results of my testing, it appears to be about one (1) second. That says it could take the 10" coil one second to pass over a target if ALL the RD time was used. 10" per second is slooooooow. (About .83 ft/sec). With that kind of RD, your target separation distance would be measured in railroad car lengths .... (It would take almost 5 seconds to make a one-way, 4-foot wide sweep ...).

    Without opening another topic, remember that Spectra is a MOTION unit in Disc mode. There comes a point when "too slow" = "bad signal". Quick test .... Throw down a quarter. Hold Spectra motionless over the quarter. What do you hear? Now, try different swing speeds and listen to the target response quality .... Enough of that ....

    To determine the "optimum" RD in terms of Adjacent Target Processing (masking), lay two coins, one coil's width apart and pass over the targets at 3 - 4", using your "normal" swing speed. Set RD so that you get two hits. Now, raise the coil and see if you continue to get two hits .... This will give you a good idea of where you should be with YOUR coil, in YOUR soil, with YOUR swing speed, YOUR sensitivity settings, etc, etc. Or, you can start at MAX RD and work down until you start to LOSE target separation. If your swing and depth are consistent (good luck unless you have a good mechanical lab setup), you should arrive at just about the same RD setting.

    If you run with TOO LITTLE RD, you can indeed lose some depth. The target will still be under the coil when the entire target cycle time has been depleted, hence Spectra will try to "see the same target twice" and will give you a very poor signal. To prove this, set RD=0 and move a target under the coil. Then, as you increase RD time, note how the target signal stabilizes, and depth returns. Now, continue to move the target away from the coil - increasing target to coil distance. Note that as you increase RD, depth does not increase. Sensitivity starts to weigh more in the equation then RD. (If Spectra can't see the target, it can't process it, so RD becomes a "non factor").

    If you laid ten Spectras side by side, all running the same programs, all using the same size coil, and ran the above tests on each one, you will find some minor deviation in the unit-to-unit results. This is MAINLY due to the variation in coil performance.

    Takeaway: Too much RD = Masking. Too little RD = depth loss. Just right RD = happy.

    Finally, again .... The chart posted is a GUIDELINE, not "The Gospel". Its a sanity check. A tool for you to use to get you close. The "optimum setting" for YOUR setup will have to be determined by YOU, using a process similar to the one above.

    Hope this is helpful. Da FoX
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    thanks fox for the in depth explaination.... it really helps a common ole dirt digger like myself accelerate the learning curve. if it wasnt for you guys on the board i dont know if id live long enough to learn all this stuff. THANKS AGAIN i think i understand it better now. good hunting

  9. #9
    Exalted One Dave's Avatar
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    Awesome Post Fox !!!

    Thank You !!
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    Bronze Member CyberSage's Avatar
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    That's some fancy math you got going on there Fox. Good stuff. I have a question concerning variations of DD coils verses concentric coils. Given that the DD has a much narrower footprint at depth wouldn't this actually throw off the above calculations. Even with my extremely slow RD of 110 I can still pick out a nickel and a quarter sitting 3.5 inches apart at about 7 inches deep. Even on a surface or air test they are clearly distinguished by the V3. It would appear that the above chart is geared more for the concentric style coil if I am understanding it correctly. Thanks for the great chart.

    Jack

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    Platinum Member rsarge1's Avatar
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    bounty hunter eagle spectrun coin master 5,000 minelab e-trac the v-3i currently the ctx 3030
    great info thanks fox
    Happy Hunting

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    Da Fox,
    Three questions:
    1. I note you used a 7.5Hz filter. How would a different filter setting change these calculated figures, if at all?
    2. And speaking of filters, has anyone done something like this chart for speed of swing of coil and filter settings?
    3. Also, if I swing relatively fast (like 3 feet/sec), but have relatively low ground mineralization, what would be a good filter setting?
    (I hope I'm not showing too much of my ignorance!)

  13. #13
    Super Moderator deolslyfox's Avatar
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    Quote Originally Posted by CyberSage View Post
    That's some fancy math you got going on there Fox. Good stuff. I have a question concerning variations of DD coils verses concentric coils. Given that the DD has a much narrower footprint at depth wouldn't this actually throw off the above calculations. Even with my extremely slow RD of 110 I can still pick out a nickel and a quarter sitting 3.5 inches apart at about 7 inches deep. Even on a surface or air test they are clearly distinguished by the V3. It would appear that the above chart is geared more for the concentric style coil if I am understanding it correctly. Thanks for the great chart.

    Jack
    Jack:

    Given that the DD has a much narrower footprint at depth wouldn't this actually throw off the above calculations.

    It would appear that the above chart is geared more for the concentric style coil ...

    The premise that the attached chart is founded upon is that (1) the coil can't see anything before or after it is over the target (discounting edge effect for purposes of this discussion) and (2) a full coil width's separation will minimize masking. You may find that you can actually reduce your delay times a bit from the settings in the table. They are given a 5% margin to address edge effect.

    Finally, again .... The chart posted is a GUIDELINE, not "The Gospel". Its a sanity check. A tool for you to use to get you close. The "optimum setting" for YOUR setup will have to be determined by YOU, using a process similar to the one above.

    And herein lies the problem with producing a "generic" chart. As noted throughout this thread, the purpose of the chart is to "get you close". I purposely did not address differences in coil configurations, but opted to use the "edge to edge" approach since that will encompass both DD and Concentric coils. No matter WHAT configuration coil, it can't see a target if it isn't over it. Conversely, the coil IS providing target information if the target is in the coil field and the unit is properly tuned. So - the "window of targeting opportunity" is never much greater or less than the width of the coil.

    While we're splitting hairs, we might as well lap and polish them too .... Hopefully the following explaination will HELP more folks then it confuses or puts to sleep .....

    You are partially correct - The pattern from a DD coil is more narrow than the cone shaped pattern of the concentric. However, as depth increases, the concentric pattern gets MORE narrow then the DD coil pattern, so there is a point where the DD's "apparent speed" across a point, graphed with that of a concentric's, will be faster, equal then slower as a function of the decrease in size of the concentric coil's pattern. These sizes and departure points will vary with coil null, size and gain settings and make for a pretty chart but not much useful data when it comes to field ops. As an "exercise" you might want to make a determination of "how wide" a DD pattern is at various sensitivities, and where the point of the concentric cone is at the same sensitivity, and then calculate the crossover points (slower / faster / equal). The dilemma starts when you ask .... What % of physical coil width would you use for the pattern width in the 10"DD? Half? Three quarters? Five-eights? What point would you consider the "significant narrowing" of the concentric coil to start? 50%? 75% Whatever you pick can either be "close enough" or "absolutely wrong", depending on the accuracy of the information that you're trying to extrapolate from the data. My goal for this exercise was "close enough to be helpful but not harmful". In other words, as you correctly noted, the RD times are a tad high, especially if you're using a DD coil. And, folks who have a propensity to "run hot and swing fast" may indeed encounter some adjacent target masking, but there is some "forgiveness" for those folks built in. Everyone should abide by my continued admonishment to use the chart / process as a guideline, and to optimize with their OWN setup.

    Now, to focus on your DD coil question from another angle. Enough testing on a sufficient universe of sample items will reveal that identical coils types do not demonstrate identical coil patterns. When tested on the identical machine, including M6 / DFX / Spectra NONE demonstrate IDENTICAL performance patterns. Close - absolutely. Within a more than reasonable manufactuing tolerance for a commercial product - absolutely. I'm talkin' 1 - 3% variance within coil type / size. So, when I put the chart together, I dusted off some old benchmark and field test data and put a little "Kentucky windage" in to accommodate those folks who are using non-V coils on their Spectra, and again, those non-V coils are both concentric and DD configured.

    As you hunt along thru life, you may find yourself compelled to take a look a what the effects of aging do to coil performance. Besides being hot, cold, wet, dry and beat on trees, coils "age" daily in an air conditioned closet. Some epoxy, like concrete, continues to "cure" over time. Solder gets brittle. Annealing cracks. The combined effects of use and time may cause a coil to "drift", or go out of null, which changes the performance parameters as well as the coil pattern. It has never been my experience that coils get "better", so there is a bit of "age bias" added in for those folks who may be using coils from their DFX days that may be 10+ years old.

    If memory serves, your sweep speed with the 10"DD coil is about 1.5 feet per second. "I would say the arc of my swing is about 4 to 5 feet. It takes me a good 3 seconds in one direction." (4+5)/3 = 1.5 ft/sec

    The chart, including the 5% edge effect bias + "stacking error" would suggest that you employ a RD setting = 123. If we take off the 5% edge effect since we're lookin' at deep targets, that would indicate a setting of about 116. Your setting is 110. (116 / 123) = 94.8%, which says the "stacking error" built into my calculations to accommodate coil size, configuration, age, V / non - V rated, depth performance, gain, pattern size and the other stuff that the "average user doesn't want / need to think about" equates to just over 5%.

    Adding the two "Kentucy windages" yeilds (5% + 5.45%) = 10.45% built in "margin".

    If we remove the total margin from the chart's recommended setting of 123 (123 * .8955) = 110.1465

    And last but not least, by way of FULL disclosure, all my calculations for this exercise were done using the ROUNDUP feature so that I continuously "erred on the high side".

    Or, if you just look at my chart, and do a rough calculation of 90% of the posted value, you will find that it is recommending a RD = 110 at your sweep speed with the 10"DD coil. (What RD setting did you say you were using? ) What your setting reveals is that you have done a process that says, "this is what works best for me and my style of hunting" and "that is is optimized for my coil size and sweep speed". A person using all your settings but who sweeps at 2 ft/sec should set RD = 92 by the chart or 83 for "optimized performance", balancing depth with target separation. You will note that the 92 setting is better for depth than the factory recommended setting of 80, but detracts somewhat from target separation. My chart - my choice - I erred on the side of depth, 'cause there's always a chance that based on sweep width, the target might be picked up "on the way back". (Explainations are much easier when you don't add all the factors attendant to that return sweep).

    Try cranking your RD = 123 and see if your performance suffers greatly .... Your depth won't, but you may see a slight decrease in target separation. Try cranking in 100 and try the same thing and see what differences in depth and target separation you encounter. It won't be much, however, if you try it with several different V and non-V rated coils, it will be different. And yes, it will be "something less than optimum".

    Another "sanity check" would be to look at the factory recommended setting in the Owner's Guide. Based on a 2 ft/sec sweep speed, most of the programs recommend a RD = 80. The chart indicates 92. Reducing that by 10% reveals a recommended setting of about 83, or within about 4% of the factory setting.

    Finally, and not to indicate that I'm any kind of a benchmark, but I have settled on a RD setting of 45 for my style, swing speed, etc, hunting with the 6X10"DD coil. The chart recommends a 49, or about 44 w/o the edge effect and other "Kentucky windages" built in.

    My goal was to help those folks who didn't know if 45 or 145 was the right number, based on their style of hunting, their coil, their settings and their ground. "If you don't know where you are, it doesn't matter which direction you take ...."

    I figured that if I can help get the folks that don't have the benefit of all your experience, knowledge and wisdom get to within 90% of where they "should be", they wouldn't take a BIG hit on either depth or target separation. From the 90% point, its just a few swings to check depth and target separation to reach "optimization".

    Hope this clears up any misunderstanding, angst or other misgivings you or other forum members from newbie to expert may have about the recommended settings.

    Good luck and good hunting. Da FoX
    Last edited by deolslyfox; 06-18-2010 at 07:47 AM.
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    jack im i wrong in thinking at depth the concentric would be narrower( meaning smaller field of view if you would),, thinking of a cone type signal versus the narrow but wider front to back of the dd... im old and confused hehe. im still trying to get constant readings past the 6 inch mark. but i am making some progress thanks to you guys

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    by the way im assuming the senior memeber under my name means you found out how old i am..........

  16. #16
    Super Moderator deolslyfox's Avatar
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    I'm not Jack, but since I started the tread I'll answer. Please read the above post, and you'll see that your question was already addressed ....

    You are partially correct - The pattern from a DD coil is more narrow than the cone shaped pattern of the concentric. However, as depth increases, the concentric pattern gets MORE narrow then the DD coil pattern, so there is a point where the DD's "apparent speed" across a point, graphed with that of a concentric's, will be faster, equal then slower as a function of the decrease in size of the concentric coil's pattern.
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  17. #17
    Super Moderator deolslyfox's Avatar
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    Quote Originally Posted by bobamis View Post
    Da Fox,
    Three questions:
    1. I note you used a 7.5Hz filter. How would a different filter setting change these calculated figures, if at all?
    2. And speaking of filters, has anyone done something like this chart for speed of swing of coil and filter settings?
    3. Also, if I swing relatively fast (like 3 feet/sec), but have relatively low ground mineralization, what would be a good filter setting?
    (I hope I'm not showing too much of my ignorance!)
    Using a different filter at any given sweep speed could help or hurt a bit. Slower filters help slower swings, and faster filters accommodate faster swings. Thats why I "stuck to the middle".

    I don't know of any charts on swing speed vs filter speed, but feel free to put one together !!!

    At your swing speed, I'd stick with the 10 / 12Hz filters. That's a pretty fast swing.
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

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    Thanks Da FoX!

    Thanks, Da FoX, for you answer. I see that you have posted a chart based on filter and swing - very helpful, especially with the personalized info above. You are a Ph.D. in metal detecting, maybe it should be Dr. Fox!

  19. #19
    Exalted One Robert's Avatar
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    I've been on RD of 45 almost since I got my V3 way back since March/April 2009...it did not take me long to find that RD 45 was my sweet spot....and this can be seen in my Old Post where I usually stated my settings...and yes I too am like Fox I use the 6x10dd v-coil 98% on all hunts with 10.0 & 12.5 filters (can't decide which I like better)...anything much higher than RD 45 is just plain way to slow for me...I'd be hunting like an old granny with no perspective of time....I just don't ever plan to hunt that freakin slow.....but...that's just My Style of hunting....that's not to say it's Yours....that's the beauty of the V3i...you have the option to set it at What You Want for Your style of hunting....so cool.

  20. #20
    Junior Member mighty_mace's Avatar
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    So what does proper target separation "sound like" ....... I tried setting two pennies side by side about a coil width apart and when i swing over them I hear a baaaahhhhhbeeep. Not beep, beep. But almost like the second hit, comes in and interrupts the first. Is this correct? I will try and tinker with the RD to see how it affects the separation, but wondered what you considered proper separation.

    I did find a penny, about 5 inches to the left of a piece of clothespin yesterday. I would hit the 70's vdi from the penny and then right to the 20's from the clothespin. After removing the clothespin target the 70's then took over. I can't remember but I think it might have only been on the one direction of the swing.....penny then pin. From pin to penny, I don't think I was getting the 70's vdi (wish i would have read this thread before finding it, lol)

  21. #21
    Super Moderator deolslyfox's Avatar
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    You should hear a definite change in tone between to dissimiliar targets. If you put two identical targets close enough together, you will most likely hear one long tone. I like to use a quarter and a nickel. That way you'll hear low - high, high - low.

    Work with your coil, your swing speed and your settings. It won't take you long to "rock it in" ....

    Hope this is helpful. Da FoX
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  22. #22
    Exalted One Robert's Avatar
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    hey mighty....if you wanna hear target separation clearly for two targets relatively close....place two different coins 3" center to center apart and swing over them with a 6x10dd coil then with the 950...you'll hear the difference really good..

  23. #23
    Bronze Member cart401's Avatar
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    Hi Fox, thanks for all your help but I'm not getting the results I should be getting with my v3i 10" DD. I have tried the test with 2 quarters, one coin width apart and changed the RD setting from top to bottom and never get a seperation between coins. Am I doing something wrong or do I have a problem with the coil? Carl

  24. #24
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    Hi Cart401,
    I'm not Fox and don't know much compared to his tremendous knowledge, but I believe the coins should be one coil apart (and maybe another inch or so), not one coin width apart.
    Bob

  25. #25
    Super Moderator deolslyfox's Avatar
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    Quote Originally Posted by cart401 View Post
    Hi Fox, thanks for all your help but I'm not getting the results I should be getting with my v3i 10" DD. I have tried the test with 2 quarters, one coin width apart and changed the RD setting from top to bottom and never get a seperation between coins. Am I doing something wrong or do I have a problem with the coil? Carl
    To determine the "optimum" RD in terms of Adjacent Target Processing (masking), lay two coins, one coil's width apart and pass over the targets at 3 - 4"...........

    Bob gave you the right answer ..... I think you might have mis-read my post. I copied the line above, just to make sure I hadn't typed "coin" instead of "coil". (Nothing would surprise me ....)

    Anyhow - what's 9.5" among friends .... right?

    This should help .... Good luck. Da FoX
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  26. #26
    Super Moderator deolslyfox's Avatar
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    Quote Originally Posted by bobamis View Post
    Hi Cart401,
    I'm not Fox and don't know much compared to his tremendous knowledge, but I believe the coins should be one coil apart (and maybe another inch or so), not one coin width apart.
    Bob
    You got it Bob !!! Thanks !!! Da FoX
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  27. #27
    Bronze Member cart401's Avatar
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    Thanks you are right, I didn't ead the word "Coil" I read the word "coi-" and assumed it was coin not coil so it is working right now. Thanks

  28. #28
    Super Moderator deolslyfox's Avatar
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    Quote Originally Posted by cart401 View Post
    Thanks you are right, I didn't ead the word "Coil" I read the word "coi-" and assumed it was coin not coil so it is working right now. Thanks
    What a difference one letter makes .... Glad its workin' for ya' !!!
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

  29. #29
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    G'day,

    This post is to say thanks to the Fox for his post and his chart.
    I know its been there for a while, but I only came across it recently and it helped define a number of things for me.
    There appear to be two ways of looking at Recovery Delays. Firstly, longer delays (a) may enable an operator to identify deeper targets, by reason of a “longer” audio signal; and (b) may mask an object adjacent to another object that may be a good target or trash.
    On the other hand – short Recovery Delays (a) may enable identification of objects in trashy ground (that might otherwise be masked); and (b) may not be long enough to enable an operator to recognise a possible target at depth.
    An essay titled “Hunting in Mineralized Ground with V3i” by Bob Canaday (the hard copy of which I printed out, but I cannot find or recall where I downloaded it) says in part –
    “...if a stronger signal is received before the end of the original target signal, the stronger signal will take over and sound off....If the new target/signal goes above the signal threshold of the older target/signal, then the new one will respond before the old signal is finished....if the new signal is weaker than the one being processed it will not be heard until the recovery delay is finished....”
    Before I had seen the Fox’s chart or Bob Canaday’s essay I fell into the trap of picking up positive signals and losing them when I changed my sweep speed for checking them.
    By trial and error going the long way around I settled on a Recovery Delay of 70 for searching and a Recovery Delay of 90 for the Analysis mode for the 10”DD coil. I may trial an increase in Recovery Delay for Analysis. Although, if you consider that the “field of vision” of a coil tapers and about halfway down the depth (the coil can achieve in quiet ground) that field of vision may be about half the physical width of the coil, so a significantly longer Recovery Delay may not be required for a target/signal that indicates as having a depth of 6” or greater (for a 10”DD coil).
    My thanks again for a very useful chart.

  30. #30
    Super Moderator deolslyfox's Avatar
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    Goldfielder .... Glad you found the chart useful .....

    Please keep in mind your physical sweep speed. A RD of 70 - 90 for your sweep speed may not be optimum for someone with a much slower / faster sweep .... That's why the chart addresses Physical Sweep Speed as well as Coil Size.

    Please note too that the feature that Bob described is NOT totally dependent on Recovery Delay. If you had a RD of 60 or a RD of 100 selected, if the two adjacent targets are close enough to trigger the override, it will occur, (stronger signal) or will not (weaker signal) until the delay period is over.

    Here's Bob's write-up for reference: http://forums.whiteselectronics.com/...round-with-V3i

    All this being said, the "trial and error" approach that you describe is exactly what the user should employ to ensure optimized performance.

    The chart, like a recipe, will "get you in the ballpark". From there you have to "season to taste".
    If there's anything I hate worse than diggin' pulltabs, its missin' a gold ring.

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