Search Coil Catalog: X-Rays, Photos and Specifications from Public Sources

[Byko]

I came across X-ray images of several search coils in this thread:

https://www.detectorprospector.com/topic/10222-whats-in-your-coil/#comments

I spent some time working out which coil each X-ray belongs to, and it grew into a catalog. Here's the first version.

If you spot any errors or have suggestions, please let me know.

The file is too large to attach here, so I've shared it on Google Drive:

https://drive.google.com/file/d/14fqMzx2hS9ljfxqU22wSQMFa2OJ4o_FY/view?usp=sharing

[Aziz]

Hi Byko,

nice, very nice. Good job!
Thank you very much.
Aziz

PS: Where are the nice forum icons?

[ivconic]

2nd page of the PDF document, the x-ray image of the coil for CZ is missing.
I personally took coil x-rays many years ago, I had a friend who was an x-ray technician at a hospital 2 km from my house.
I even have the original x-ray somewhere in the boxes.
I posted all that here on the forum a long time ago, but now it's hard to find.
In the meantime, the forum has undergone many changes and several hacker attacks, which further complicates the search for content that is 15, 20 or more years old.
Here is an image to supplement the PDF document.

[Asgard]

Good job! Alexandre

[Byko]

ivconic, thank you for sharing. Your X-ray is now included in Coils Atlas v2.

[Byko]

I'm pleased to share the coils atlas v2

https://drive.google.com/file/d/1N840ts8ljF5B3jAexNT1Jg0q88YhmufJ/view?usp=drive_link

If you have any coil data, pin map etc. - please share. I'll add it to the next revision of the atlas.

The changes compared to previous version:

v2 — 43 pages, as it stands 9 October 2026. Changes against v1:
Renamed. "X-Ray of metal-detector search coils — atlas" → "Metal-detector search coils — construction atlas": the document outgrew the original name, which described only the X-ray
column.
Numbering and order. The index page now counts as #1. Coil pages are grouped by type in order of popularity — DD, then SUPER-D (a DD variant, kept with the DD family), then CC,
then MONO — and within each type by manufacturer, then size, with a clone right after its original.
v1 → v2 page numbers: 1→29, 2→28, 3→35, 4→27, 5→32, 6→33, 7→34, 8→3, 9→17, 10→5, 11→6, 12→15, 13→16, 14→18, 15→19, 16→22, 17→10, 18→20, 19→21, 20→11,
21→12, 22→13, 23→14, 24→7, 25→23, 26→24, 27→4, 28→25, 29→2, 30→36, 31→38, 32→40, 33→39, 34→37, 35→26.
New pages. #8 MD6450 11-inch DD, a Chinese CLONE of the Garrett ACE 8.5×11" DD (no X-ray): the compiler's own photos and measurements (L, Rdc, Resr, pin map, pin-to-pin
capacitances, D size and overlap). · #9 Garrett AT 8.5×11" PROformance DD Submersible (PN 2222400), stock on AT Pro (no X-ray): top view, Fuma's coil schematic and alexkim's
redraw, opened-coil and board photos, measured TX/RX, the RX capacitor inside the coil, and Garrett's shield-on-TX connection. · #30 Garrett ACE 6.5×9" PROformance CONCENTRIC
(PN 2221700), stock on ACE 250 (no X-ray): Ivan Kostin's photos of the opened coil, two coil schematics (factory winding; Ivan Kostin's rewind), Garrett top-view photo and specs, with
the pin-number correction, measured L/R, and the note that the resonance capacitors are in the detector, not in the coil. · #31 Raider MD-6250, a Chinese CLONE of the ACE 250 stock
coil (no X-ray): top-view and opened-coil photos. · #41 Minelab Multi-IQ / Multi-IQ+ TX table — TX coil L/R, drive voltage, spike tips and driver stage per machine (X-Terra Pro / Elite,
Equinox 600/800/700/900, Vanquish, Manticore), with sources (Carl-NC and JoyJo, Geotech1 453141; Skippy, Geotech1 15888; lovecpokladu.cz videos). · #43 this revision history.
Measured geometry added on 16 pages: winding outer envelope, how far the winding sits inside the shell, inner RX loop where a concentric allows it, and the TX/RX overlap at the
centre. Every one of the 25 DD pages now states an overlap: measured on 16 coils (8.8–17.3 % of the span it crosses, median 11.5 %), with the size of one D beside it — half that
span plus half the overlap. Five say it is not measurable from that plate and give the reason; three have no X-ray; #8 is measured by hand on the coil itself (32 mm). The percentage is
taken against the span the overlap actually crosses, which on an elliptical coil is the short axis; v1 quoted three of these against the long axis instead.
Turns estimated where the inductance is published (#7, #18, #19). The published L and DC resistance are solved together for the number of turns and the wire gauge, using the loop
size from this atlas’s own measured D geometry; nothing is fitted. Checked against a coil whose winding is known — a 190 mm DD of 58 t / 0.50 mm and 200 t / 0.30 mm — it recovers
turns to 3 % and wire diameter to 4 %. On two of the three coils it also predicts a bundle thickness matching the one measured off the plate to 0.01 mm. Treat the figures as ±10 %: they
are estimates, not counts.
Overlap shape recorded on all 25 DD pages — EYE, PARALLEL, SEMI-PARALLEL, IRREGULAR, or not determinable where no X-ray or photograph shows the windings. Read off
each plate. The shape is what decides whether a single “overlap at the centre” figure means anything: a parallel pair gives a band of constant width, while an eye closes to nothing at the
crossings, so its width depends on where it is measured. That is why five coils carry an overlap figure and the rest do not.
Disclaimer added on page 1, above the index: these dimensions are estimates.
Figures that did not survive checking were withdrawn, not rounded. Two winding envelopes (a stitched plate and an over-sized shell fit) are withdrawn. Two overlaps withdrawn on
the first audit were re-measured and are published (#3, #13). Where an overlap could not be had at all the page says so and why — a stitched plate (#20, #26), a coil clipped by the plate
edge (#21), or a fit that does not follow the windings (#24, #25).
#29 Fisher CZ-3D — X-ray added (v1 had "NO X-RAY"), contributed by ivconic (his own X-ray); pen notes outside the coil removed digitally; the image was then re-oriented (rotated 180°
and mirrored) to match its top-view photo.
#27 Fisher Gold Bug 2 6.5″ — files renamed from "6-inch" to "6.5x3.4-inch": the coil is 6.5″ and elliptical, and the short axis is now measured (3.38″).
#6 Coiltek 10×5 NOX — the stock EQX 11 TX reference was "119 µH, ≈0.35 Ω; TX >10 V square wave ≤40 kHz". It now gives both measurements (103.7 µH / 0.52 Ω, Carl-NC; 119 µH /
≈0.35 Ω, Skippy) and the Equinox 700 drive of ±12.2 V bipolar PWM.
#7 Garrett ACE 8.5×11" DD — a note that the ACE 250's stock coil is a different, concentric coil (#30).
#13 Minelab EQX 06 — the Equinox system TX line was updated from ">10 V square wave" to the Equinox 700 ±12.2 V bipolar PWM figure.
#16 Minelab V10 — added the Vanquish TX driver (full bridge, per JoyJo, no source given); TX drive voltage NOT FOUND.
#18 Minelab EQX 11 — TX L/R now gives Carl-NC's 103.7 µH / 0.52 Ω beside Skippy's 119 µH / 0.35 Ω; the 700/900 coil is marked NOT MEASURED. The drive line was ">10 V square
wave ≤40 kHz" and now gives measured drive levels (Equinox 700 ±12.2 V, X-Terra Elite ±9 V) and the disputed driver stage. The RX preamp line no longer states a gain (v1 said G≈16;
now "gain NOT PUBLISHED", OPA2835 unconfirmed). A third internals image was added: the RX preamp schematic (Foma / dbanner, known to contain errors).
#19 Minelab M11 — v1 said "L/R, turns, TX drive: NOT FOUND". Now TX L = 174.5 µH, R = 0.59 Ω (Carl-NC), drive ±22 V with spikes ≈ ±48–50 V, and the suspected driver stage.
Sources reworded for sharing: references to material held only in the compiler's folders, and to files not reproduced in this atlas, were removed or replaced by the underlying public
citation.