Greg Payne

Some years ago, in I remember having a conversation with some friends and discussing whether a ‘computer-on-a-stick’ type of detector would ever be possible. At the time, the general consensus of opinion was that it would be well into the 21st century before we saw such a thing.. if at all.

Two serious obstacles seemed to be standing in the way. One of these was the sheer weight and bulk of the circuitry required; the other obstacle was that we felt a computerised detector would be so expensive that nobody would be able to afford to buy one. Well, it just shows how difficult it is to predict the future!

Things have changed greatly in computer technology in the last few years both in terms of miniaturisation and affordability. The Eagle Spectrum is in many respects just like the detector that we envisaged — but never thought possible — ten years ago. Where it does vary is that it exceeds in its functions and facilities anything we could have imagined at the time.

When working on these Field Tests, there never seems to be enough time available to really be able to put a machine ‘through its paces’ on all the different types of sites. To date I have only been able to log up around twelve hours of searching with the Spectrum, in two outings on farmland.

As the Spectrum is a somewhat complex detector, I therefore intend to make this a two-part test. This present part will cover general information and the ‘Preset Programs’. In the second part of the test, which will be published in a few months time, I hope to be able to write in detail about the ‘Pro Options’ and such facilities, and should by then have been able to assess the Spectrum,’s performance on beaches and

sites other than farmland.


User Suitability


The Spectrum is far from being a ‘switch on and go machine.

Although whites have done there best to make it user friendly it does require a certain amount of blood sweat and tears to be able to get the best from it.

There are therefore two sensible questions that any would-be purchaser should ask

Is it necessary to make a detector so complex?

(2) What does the Spectrum offer that makes it perform better than a detector that has far simpler controls and Which does not need the learning effort?

Well, let me first say that if you own a computer and are at home with such terms as ‘RAM’. ‘DOS’ and ‘megabytes’ you should, even if you haven’t used a detector before, take to the Spectrum like a ‘duck to water’. It is certainly a lot easier to use and operate than most computers. If, on the other hand, you do not like modern technology and have trouble setting up the timer on your video recorder, it might be better for you to consider buying one of the simpler but effective, detectors in the White’s range which have the normal manual controls.

So the answer to the first question, is that while the Spectrum may be complex to some it is simple to others; if you have any doubts about it, go for a normal machine. If you are at home with computer technology then the Spectrum offers lots of facilities and variations in settings that were previously only available to those working in electronics laboratories, designing and building detectors.

It you are familiar with the technology, or are willing to come to terms with it, the Spectrum is a detector that comes almost in electronic ‘kit’ form; by the use of the ‘Custom Programs’ and ‘Pro Options’ it is possible to turn the Spectrum into a motion detector, a meter discriminator or whatever is applicable to the type of site you are searching.

As to the second question which is basically ‘Is all the learning effort worthwhile for what the detector has to offer?’, the answer must be ‘Yes’.

Where the Spectrum excels is in the amount of information it can supply about a target before the user decides whether or not to dig it up. Mark Rowan, the design engineer behind this detector states’ our customers wanted all the information technologically available about the target, beyond just a VDI number. Multiple phase angles, dynamic phase responses... but in an easy-to-understand display. That’s the concept behind the Eagle Spectrum’.

The Spectrum provides the user with four ways to determine the nature of a

target: 1. Audio discrimination;

2. Three digit VDI reference numbers;

3. An ID label print out on the display (including junk items); and 4. The new Spectrum analyzer that gives graphic patterns which become the ‘signature’ of the target.

One of the most visual benefits of the Spectrum graph is the ability to show a ‘smear’ pattern on iron targets that can often fool other methods of identification. An iron target will most likely show definite bars on both the negative and positive sides of the Spectrum graph often smearing all the way across the entire chart. Valuable targets will not produce such obviously wide patterns.

To quote Mark Rowen again: ‘The Spectrum makes use of a new way of displaying information about targets —the ‘Spectrum Graph’ or ‘Phase Spectrum Analyzer’ which shows the operator everything we know how to display about the characteristics of metallic objects in the ground. The Spectrum is a very ‘smart’ detector but it is also an ‘honest’ one. Having done the best it can to determine the probable identity of a target, the Spectrum gives you all the information you need to make your own decision (human beings are, despite what you might have heard, still a whole lot smarter than computers) to dig, or not to dig’.

Although I have only so far put in twelve hours of searching with the Spectrum, during that time — and quite a few signals — not a single unwanted target was dug up.




The Spectrum has none of the usual controls on its main ‘box’. Instead, its many functions are controlled by five push pads and a trigger switch; all of these are located within easy reach around the meter housing. The functions of the controls are as follows:—

On/Off: When pressed, this turns on the instrument and starts the battery test and ground balance sequence.

Up and Down Arrows: When pushed, these ‘scroll’ the pointer up and down the selection from the menu. They will also return the detector to the last used screen.

Menu: When pushed, this activates a selection from the menu. It can also be used to return the’ detector to the ground balance sequence.

Trigger Switch: Unlike the other controls, this is a mechanical spring-loaded switch. It is located under the meter housing. When pulled towards the user and held in, this switch puts the detector into pinpoint and depth reading mode. Pulling and releasing this control in field use also clears the screen of previous readings (although this normally happens automatically on a timed ‘fade’ system).

Turning on and setting up the Spectrum is fairly simple once you become accustomed to using push pads rather than the more normal manual rotary controls. The sequence (printed for instant reference on the main box) is described below.

The user first pushes the ‘On/Off’ control. The Spectrum will come up with a brief opening display listing its software version. The detector will then automatically go from this to its battery check display and will indicate battery condition in volts. With rechargeables this should be around the 4.9 volt mark. The lowest usable voltage level is 3.8 volts at which point the display will show the warning of ‘Low Battery’.

Following the battery check the Spectrum will stop at the first page of the program display. This will give a choice of three preset programs: Coin & Jewelry; Jewelry & Beach; and Relic. In terms of usefulness to British enthusiasts, these are the main presets that will be employed. (The second page of the menu gives a preset option of Prospecting — more useful for gold nugget hunting than normal detecting —and two ‘Custom’ programs which will be dealt with in Part 2 of this test).

By using the down arrow push pad a program is selected and then confirmed by pushing the ‘Enter’ control. The detector now goes into an automatic sequence of ground balancing. At first the display will read ‘Raise loop to waist level, then push enter’. This will ‘air balance’ the detector in preparation to be ground balanced. During this procedure the detector will self-adjust for internal temperature changes and other variables. A double ‘beep’ sound will show that this instruction has been carried out and the detector will continue by stating ‘Lower loop to ground surfaces then push enter’. If ground balancing is successful another double ‘beep’ sound will be heard. If for any reason the Spectrum cannot ground balance (i.e. there is a piece of metal in the ground immediately under the area concerned) it will give multiple ‘beeps’ and the user needs to push the ‘Enter’ ControI and ground balance in a different spot on the soil. Once this has been carried out the detector is ready for use and will show its normal search display.

It takes quite a few words to describe this procedure, but in the field the whole sequence takes less than a minute.

Once having gained a little familiarity with the Spectrum, there are some basic adjustments that can be made in conjunction with the preset program you have selected. Access to this facility is gained by pressing ‘Menu,’ which will ‘cause the Main Menu to be shown on the display, and then selecting ‘Basic Adjust’. There are nine types of basic adjustment possible, these being

shown on three pages to menu. They are: Volume, Threshold, Tone Adjust, Audio Disc., Silent Search, Mixed-Mode Audio, AC (motion) Sens, DC (non-motion) Sens, and Backlight.


Preset Programs

As stated, the Spectrum comes supplied with four preset programs. These are contained in the ‘ROM’ (Read Only Memory) part of the detector’s circuitry and are thus permanently installed. The suggested uses of the preset programs are as follows:— Coin & Jewelry: This program will

cause the detector (by means of selected notch settings) to reject junk items such as nails, foil, ring pulls etc, while still responding to most coins and many items of jewelry. It is a good program for very heavily contaminated coinshooting areas (parks, commons etc) but the use of it could result in a certain amount of wanted targets, such as cupro-nickel coins and thin-section 9ct gold rings, being rejected.

Jewelry & Beach: This is similar to the first program but provides far less discrimination and there is thus less chance of missing rings or other wanted targets that may fall close on the scale to junk. This is not just a beach program, it can be used on inland coinshooting sites where less discrimination is required than that offered by the first program.

Relic: This program allows the detector to respond to all metals except small iron items such as nails. Large iron will come through on audio but will show as ferrous on the bar graph. In America, this program was designed for ‘relic hunting’. In Britain it would be the chosen preset program for farmland until the user became familiar enough with the Spectrum to be able to install his own custom programs.

Prospecting: This program was mainly intended for gold nugget hunting and there is unfortunately not much in the way of such natural gold in Britain. All metals respond with an audio signal but the display will only show a VDI number for metals that could be gold.


The Eagle Spectrum follows the modern style of design in having a cranked upper stem and built-in armrest. However, it is neither as compact nor as lightweight as many other machines on the market. Even in these days of miniaturisation, the advanced computerised functions available on this detector do require a fair amount of circuitry and components, and this is reflected in the size and weight of the machine. (the real miracle is how it has been possible to get a detector to do so much in such a small space!)

Although reasonably well-balanced

this detector is without doubt heavy and while I can normally search all day without feeling any strain on my arm, after two or three hours I was beginning to notice the weight of the Spectrum. There is an easy way round this, of course, and that is to go for a hip-mount option as will be covered later.

The Spectrum is well engineered and up to White’s usual high quality of construction. The photographs with this report will show better than words the general shape and design of the detector. Basically, it has a black 9.5 inch

‘polo’ loop as standard, a plastic isolator lower stem segment, and then two black anodised aluminum stem sections that terminate at the main box (which is of aluminium). The stem segments are locked together and adjusted by the push-button system.

A number of quick-reference instructions are transfer printed in white onto the main box. On the left is a table showing the VDI scale, and what the various numbers are likely to represent.

On the right are other panels showing the initial ‘Start Up Procedure’ and other operations. On the underside of the main box are to be found the options contained within each page of the various menus.


Hip Mount Versions

As stated, the Eagle Spectrum is something of a heavy detector. If you intend to use it no more than an hour or two at a time, then this would be no problem, but for all day use of seven or eight hours continuous searching you might find that it does cause some arm fatigue.

In recognition of this, White’s market the Spectrum in two hip mount versions. The first of these is simply in the form of an accessory kit, costing £27.50, to convert the standard Spectrum. This allows the detector to be quickly changed to hip mount form, and equally as quickly changed back to the standard detector.

The other option is to go for the new Sierra Eagle Spectrum which White’s

describe as a ‘designated hip mount’. By this they mean that the detector is made specifically to be used in hip mount form and cannot be converted to a standard hand held format. This version has its meter mounted closer to the main box, and angled for easy viewing. As the ‘heart’ of this detector is its meter this is a sensible idea and a good option to go for. The Sierra also comes with a weather resistant box cover and improved pinpointing; it does, however, cost an extra £70 over the price of the standard Spectrum.

Some people, I know, seem to have a bias against hip mount detectors. But when such people are questioned more closely it usually turns out that they have never actually used a detector in this form and for some reason or other, just don’t like the idea. If you fall into this category, you should at least be prepared to give hip mount detectors a try. The advantages are many, not least of all that you are only swinging a stem and search head, and this is so light it causes no fatigue at all.

I have also heard people comment that the coil lead would get in the way when they were trying to dig up finds. Well, this is just not the case. The coil lead is far more manageable than the headphone lead you would normally have to deal with, and if you should snag this then at least it doesn’t ‘pull your ears off’ as is the case with a headphone lead. So, don’t knock hip mounts until you have tried one. Once having owned a detector in this form, most enthusiasts would never L se anything else.

With the Spectrum, the hip mount option (either version) certainly cures the problem of weight, and it makes the all-important meter that much easier to see and work with.


Field Appraisal

The first site chosen for testing the Spectrum was an arable field. This had recently been deep-ploughed and was far from ideal conditions for an. detector to work under . . . to say nothing of the user! It was more or less a case of jumping from ridge to ridge rather than the usual walking and careful sweeping.

For this situation I chose the Relic’ preset program which only takes out a certain amount of the small iron. The threshold tone installed within this program is quite high, and the instruction book recommends that it is left that way in order to gain a sense of the ground in terms of mineralisation and iron content. However, I found this high threshold a little irritating and after a few minutes selected the ‘Basic Adjustments’ menu and dropped it down to the ‘1’ setting. This gave a faint threshold tone that could still be heard rising and falling but was more in the background and less of a distraction. It would also have been possible to have

selected ‘0’ and have taken off the threshold altogether without affecting the detector’s performance.

Although I had tried one or two ‘bench test’ experiments with the Spectrum at home, I went out not really knowing what to expect from the detector in actual use. One thing I did notice was that once set up, there is little else you need to do in the way of further adjustments. Also, the detector was far less complicated to use than I would have expected.

The ‘heart’ of the Spectrum is the bar graph and within ten minutes I was getting to know and value this facility, and what it was trying to tell me. Basically, as this was farmland it was a simple case of digging up any target registering on the bar graph above the middle ‘zero’ point. The few large pieces of iron that did break through on the audio gave a very obvious ‘signature’ on the bar graph (e.g. blocks on the lower left, blocks lower left and high right, or ‘smeared’ right across the scale); Wanted non-ferrous targets, on the other hand, would register above the ‘zero’ point only. To check this out, I did dig up a few signals to confirm that they were indeed iron as the meter was telling me. After this, I am pleased to

say, I was bothered by no iron at all even large or deep pieces.

As I did not have to cope with foil or ring pulls, all non-ferrous targets were dug without much attention to the VDI number they were showing on the meter. This part of the display would, I imagine, assume much greater importance if you were searching a coinshooting site or beach, where non-ferrous junk is in such abundance as to be a nuisance.

My first finds were some lead unofficial farm weights and then, after no more than fifteen minutes from first switching on, a clear signal produced a really nice hammered silver half-groat of James I. This was only about 3 inches down but the ploughed field did present difficult conditions. Quite a few other detectors may have been able to find this

coin, but it was found by the Spectrum and as you can imagine my respect for the detector certainly increased from this point. Although no more hammered came up on this particular search, a few other odds and ends (mostly lead weights) did turn up on a field known to be sparse in finds.

The second area chosen was again arable land, but this time ploughed and rolled, and therefore much easier to search. This field did show signs of previous buildings (by the tiles fragments and patches of dark soil) which subsequent finds suggested to have been stables or barns. No hammered came from this site but finds were far more plentiful and included a fish scale crotal bell (late 16th century to early 17th century), a William Ill farthing, and several dozen buttons of 17th and 18th century date (including some decorative dandy types).

Once again no iron was dug and all the non-ferrous targets were clearly indicated as such on the bar graph.

Some of the finds were coming up at respectable but not exceptional depths However, my use of the Spectrum has so far been limited to the preset programs which have been devised to be easy for beginners to use. I have been told by experienced Spectrum users that far greater depths are possible with the custom programs and I will report back on this in the second part of this test.


As mentioned earlier, I believe the Spectrum to be a detector that is best suited to a user familiar with computer technology or one who has some previous detecting experience with a standard machine and is willing to come to grips with unfamiliar controls and terminology for the undoubted benefits that would result.

The Spectrum is a fairly heavy machine in its standard form, and if I were buying one for my own use I would chose the Sierra hip mount version.

In previous Field Tests I have tried to point out particular uses for a detector in recognition of its outstanding performance abilities. As stated before, when doing this lam not saying that the detector concerned would not work well on other sites; I am merely trying to point out areas where a machine would excel.

The Spectrum offers two outstanding benefits. One of these is that it is programmable (if you are willing to put the time and experimentation required into doing this). This aspect will be covered in the second part of this test. The second benefit is that of the advanced meter system that provides the user a great deal of information about any possible target, before his trowel touches the ground.

During any particular detecting session a great deal of time can be wasted digging up junk. With a good meter analyzer such as the Spectrum that can be avoided, which leaves more time for digging up wanted items. And the more non-ferrous signals dug up the more chance of success and finding some-thing really nice. Digging up junk all day, can also prove extremely frustrating eventually ... even to those with the patience of a saint.

So, where the Spectrum will particularly excel is on those sites where junk

contamination is a particular nuisance. It is good at avoiding iron but more than that it will allow you to avoid silver paper, foil, ring pulls and other nonferrous junk with minimal accidental rejection of wanted finds. Besides the normal type of junk it will give a clear indication of 12 bore shotgun shells, low denomination decimal coins, .303 rifle cartridges, and even muskets balls where these are so prolific as to waste digging time and prevent you getting to

the better finds.


Model: Eagle Spectrum

Manufacturers: White’s Electronics

(UK) Ltd,13 Harbour Road, Inverness

IV1 lAY (tel 0463—223456).

Recommended Retail Price: (effective

from 1 July 1993) Eagle Spectrum £680

(inc VAT). Sierra Eagle Spectrum £750

(inc VAT).

Both prices include charger, rechargeable batteries, and headset.

Batteries: Rechargeable battery supplied, and back-up dry cell battery holder to take four alkaline ‘C’ cell batteries.

Battery Ufe: 8 hours (rechargeable pack)

Search Coil: 9.5 inch, polo

Accessories: Discharger/Recharger £27.50; Bluemax Loop 600 £50; 950 Loop Cover (black) £5.50; 6 inch Loop Cover (black) £4; Wall/Detector Stand £3.90; Hipmount Conversion £27.50; Loop Stabiliser Bracket £3.95: Hardtop Case £47.50; Carry All Bag £38.50; Box Cover £15.75; Meter Filter Kit £5.95; 8 inch Bluemax Loop £50; and Car Battery Charger £17. All prices include VAT.