Multi-freq operation is definitely the Equinox’s strong suit, in my opinion, and like you, it’s my go-to mode for hunting whenever possible. The exceptions are if I’m on a site where EMI creates too much interference, I’ll switch to an unaffected single freq. Or when I
really do want to squeeze some extra depth out of a previously hunted site, 5 kHz gets dialed in (now maybe 4 kHz
).
I don’t really expect 4kHz to add anything Earth-shattering for us - it’s surely too close to 5 kHz to make any real noticeable depth difference between the two. But I like the idea of having an extra option - if 5kHz is zapped by EMI, maybe 4kHz will be spared, and I can select that to hunt.
And no, my understanding is that 4kHz is a single freq option only, and in no way is it currently incorporated into Multi. Neither is 5kHz, or any of the other selectable single frequencies for that matter, except in Gold mode! It’s a common misconception that the Equinox uses all 5 single frequencies simultaneously in Multi.
It has been determined through oscilloscope analysis that the Equinox transmits two primary frequencies in each Multi mode. Carl Moreland, who was a senior engineer at Whites and First Texas has broken the results down like this:
Park & Field modes: 7.8kHz + 39kHz
Beach modes: 7.8kHz + 18.2kHz
Gold modes: 40kHz + 5kHz
It can be tough finding good links that show this information concisely. A lot of the stuff gets pretty technical and is for folks with larger hat sizes than me, but this is the best I could track down so far:
Geotech Forum: Minelab Equinox 800 Frequency (requires creating a free user account if you don’t already have one)
Detectorprospector.com forum: Multi IQ Spectrum Test
Detectorprospector.com forum: Minelab Multi-frequency
Regardless of the transmitted frequencies, the real secret sauce is how the received signals are processed and weighted.