Hi Cowboy,
Welcome to the TNet.
It's been many long years since I used this unit, but I rank it as my absolute favourite for coin hunting. I'll try to remember what might be useful to you, and make some helpful suggestions.
I used the Eagle Spectrum for quite a number of years. It's very similar to it's successor, the Spectrum XLT...which I currently own and used both for some coin hunting many years back, and checking large iron signals in prospecting environs in recent years. These are excellent general purpose units, providing reasonable depths, very stable and smooth operation, with effective discrimination, and excellent iron resolution. I think the Eagle Spectrum was a slightly deeper seeking unit, but cannot substantiate that comment.
The earlier post here covered off a good point about coils. I'm not familiar with your coil but presume it's about 5" diameter and should be an advantage for target separation over the stock. I suggest you get the stock coil if you wish to get better coverage and depth. Check with White's, and ask about the Blue Max 950 Loop (6.59 kHz).
You didn't mention the ground phase for the area you hunt; iron minerals in the soil play a major role in terms of the depth you can expect with any VLF unit. Four inches with the small coil doesn't sound too far off, but I believe it will go a bit deeper. My experience in fairly high mineralized ground (Ground Phase @ minus 93) with the 950 stock coil was typically 5" and sometimes 6" generally on penny/dime size targets. There are always exceptions, and I experienced a few as well, getting 7" to 8" on silver dimes and quarters in good topsoil (not dominated by high iron brown clay that we see in these parts a lot) conditions.
Quoting you:
"Living in an apartment building, I can't exactly go out into the backyard and dig up a section of ground to make a test area.
What would be the best way in this circumstance, to test the different settings so I can see if I am in fact getting decent depth, or if I am just skimming the surface?
Are there any custom programs out there that someone has used successfully with this particular model?"
First question, you could go to out of the way spots and bury targets at different depths and see how the unit responds. This method will not reproduce "real world" depth/discrimination/identification results...and may leave you discontent with the apparent (lack of) capability of your unit (it's a viable test for checking "relative" depth performance between units only). Your results in "undisturbed ground" will be significantly improved. That's a personal view and nothing else.
2nd question: here are some thoughts that might be of help, although I suspect some folks will disagree on a few. That's fine, these tips will help you to some extent I think. Only thing is, I don't remember anymore about how that unit's programs are saved. Here we go........
(1) make a point of using the original programs to create your own customized programs, label and save them so you know what they are for, ie parks, prospecting, the beach, relic hunting and so on. This step helps to eliminate fooling around on site with the menu system, since you can use the shortcut keys, especially the up/down keys to return to your last menu parameter setting. In the field, normally I then only adjust the AC Sensitivity according to the ground minerals or what I can put up with, and access it simply by pushing either the up or down arrow key.
(2) adjust your autotrack offset to track slightly positive (plus one will do fine) to provide a slight enhancement especially on small target signals; not too much, otherwise the ground will sound off as a target whenever you pull the pinpoint trigger to check targets.
(3) run the sensitivity as high as possible without getting unstable operation, which with this particular unit, will initially mostly present itself in the guise of jumpy VDI indications before the audio will start acting up. Despite a separate adjustment ability for VDI Sens and AC sens, these sens settings are related insofar as AC Sens will affect the VDI sens. Keep it in mind before you jack-up the VDI sens setting.
(4) I prefer modulation on targets, it's an audio aid on target depth; but if you turn it off, all signals will read with the same volume regardless of depth...which many do prefer; some consider it an "edge" to aid hearing even the faintest targets. It's a matter of debate and we'll leave the subject right there. Your choice.
(5) pre-amp gain increases the signal strength transmitted and will give you more depth to a point, but don't overdo it or the machine will be unstable, and prone to overloading. Generally keep it at a setting between one and three in your primary custom coin hunting program, (can't remember the scale for that unit, so I'm basing these remarks on the assumption the scale runs from "1 to 10"), and where condtions permit...try higher settings and see what you think you can put up with in terms of stability. Remember to ground balance whenever you change the pre-amp gain setting.
(6) if the area is not too laden with signals try out the all-metal mode by simply turning off the audio discrimination under basic adjustments; the unit will still give visual ID. The all-metal motion mode will provide practically useful extra depth over the disc mode with this particular unit, but keep in mind the visual ID display will not go as deep as the audio (this applies to any mode).
(7) I preferred not to use tone ID on this unit; tone ID is not as reliable on deeper targets, particularly in highly mineralized soils, and in disturbed ground such as ploughed farmfields. In undisturbed "park" type ground settings, many deep coin size targets will read close to or at the correct conductivity. However, some deep coins may respond as iron, or perhaps are classed under VDI +95, or otherwise may respond erratically. By using the single tone , you are alerted to a deeper target's presence, and to at least check out the signal with your pinpoint trigger to determine the depth. If it's deep, dig it.. period. VDI +95 is tricky....shallow (a few inches) forget it....deep, dig it. Oftentimes at the fringe of the unit's
visual depth capability it'll still pick up a silver dime at 7 inches with a solid, quite modulated two-way signal, but won't be able to properly classify it. I've found more often than not, at this "fringe" depth, the unit will place it under VDI 95.
8. if you're in an iron infested area, ie relic hunting, pay attention to the signagraph for bars on the left side, or, scattered right across the entire screen, for iron ID. The signagraph is reliable, and more dependable than the audio discrimination for iron ID. The signagraph will continue to present iron info no matter where your disc VDI settings are set. It's so dependable on
large iron, I use it as a backcheck on large iron in mine tailings, to save a lot of digging. I've checked these large iron readings innumerable times, and it has always been spot on. The only "if" is that you do have to ensure it's a decent signal in order to get a reliable reading (that's regardless of whether it's a broken signal or not, although as you know, an audio broken signal usually indicates trash at shallow depths, but a deep broken signal, especially if well modulated...means dig it). Can't tell you the many broken signals and "ticky" signals at depth that resulted in coin finds.
(9) ensure "transmit boost" is always turned on, period.
(10) never use discrimination VDI settings beyond mid-foil range in general park-like hunting...and less or none in totlots; use the audio for analyzing signals, use your meter to determine where the target identifies and use your judgement to decide whether to dig. I prefer to keep my settings no higher than minus 30 to ensure better depth and cleaner signals, unless it's full of trashy signals, then to save sanity, I'll up the disc to about "plus 9", and no more. Less disc = more depth. Again, set up your custom programs to accomodate these settings, so there's no fooling around with the menu in the field. Also remember to keep VDI plus 95 enabled; otherwise depth on silver/copper coins and tokens will be reduced slightly.
(11) set your threshold to "1" and leave it there. This provides best hearing sensitivity to targets, particularly in the all-metal mode. When using the all metal mode, try leaving the SAT control set to about "8"; reading the manual, you may think that's too high. It isn't, and you will agree once in a typical park setting (with multi-signals everywhere, you will want the quicker speed for better separation of targets). Besides, you'll still get better depth than with disc modes on this unit.
(12) keep bottlecap reject setting very low ie. "1, or 2"; any higher, and you start discing out deeper desirable targets. Experiment with it, and you'll agree. This unit's iron discrimination is very good, but it too can be fooled by "round" iron...and that means bottle caps as well. Generally, leave the "recovery rate at the default setting; if you want better separation, use a smaller coil. My perception was that substantially increase RR resulted in dirtier signal clarity and decreased depth. In an area where signals are few and far between, consider decreasing the recovery rate for marginally better target ID, and depth. Again, that's my personal view and nothing else.
That's about all I can think of for the moment. You may wish to include some of those ideas/thoughts into your custom programs. See ya and good luck Cowboy,
Jim.
