The Sierra Madre uses the 6.592 khz frequency and shares part of the electronics of the XL PRO, in it's final guise the machines use the same battery system and box as the Xl Pro, MXT etc. Coils that can be used range from the 25" Magnum Force, the White's 9.5, 800, 5.3 and Snooper 350, even the Bluemax 6x4 DD works as well as Bigfoot etc .. ALL Bluemax compatible coils work.
The Sierra Madre takes the surplus XL PRO circuit boards without ID meter, no Disc circuit, no TR circuit no SAT or hot rock reject modes etc. Just pure all metal mode remains and auto ground tracking with an option to lock. Gain or sensitivity are not dialled in, it's either a high or low switch.. The machine is used to locate steel pipes etc, it's an industrial machine. So it has it's limitations. Put the right coil on it and you've got an all metal machine with limited controls. No target id, something that is the VLF machines greatest asset.
Now I use the Xl Pro in Australia, to operate smoothly you really need to have control over sensitivity or gain, use the SAT mode and even the option of hot rock reject, none of these controls are on the Sierra Madre. It is limited to High or Low gain.. not ideal. as a detector it would be awkward and hampered for lack of fine tuning and control. Great as a pipe locator, which is what it was designed for. Just go to the White's website and download the manual for the Sierra Madre and you will see it's limitations. There are much better options..
In my experience the Xl Pro has a lot of power and so would the Sierra Madre, under the right conditions they can go very deep. Rarely will ground conditions allow you to use all the sensitivity or gain that is available. Use a smaller coil like the 5.3 or well shielded Royal 800 and sometimes I can get gain very high with spectacular results. It shines in low mineral areas, loves the dry beach sands, parks etc. You can run the Xl Pro in all metal with SAT and the meter will id iron and hot rocks accurately. No such option with the Sierra Madre.. Like all VLF machines hot rocks and iron stone, heavy mineralized soils are problems that can be managed but not completely overcome, again the lack of controls hampers such efforts with the Sierra Madre.. it is only a pipe locator after all..
Four of five feet in the air using a 9.5 coil on a metal gold pan, yes. In the ground? You dig the hole and we'll find out.. but why bother.
Karelian