Just to throw in my two cents...
Noise cancelling is of course an attempt to mitigate
the effects of EMI, with respect to target signals.
Ground balancing is of course an attempt to mitigate
the effects of ground minerals, with respect to target signals.
The source of EMI is NOT the ground (unless you are dealing with buried electric lines, underground dog fences, etc.) So -- noise cancelling "near the ground" is not "more beneficial, in any way -- due to the fact that, again, the ground is not the source of EMI most of the time. Conversely, since sources of EMI normally reside
above ground, one can arguably "sample," or "receive" more of the EMI that is present by holding the coil
above the ground.
In fact -- let's say for the sake of argument that the source of EMI in a given spot is a lone building, which has a wireless router turned on, and broadcasting WiFi signal. In that case, assuming that this lone building's WiFi signal is the main source of EMI in that area, aiming your coil directly AT the lone building, so as to allow the machine to "most effectively sample" the EMI being transmitted, might make sense -- and some argue that it IS a good way to allow a machine to most effectively mitigate EMI.
However, since we often don't know the location of the source of the EMI, and since more often than not, there are MULTIPLE sources, then it makes sense that just "holding your coil above the ground," perhaps at waist height, would be a reasonably good way to run a noise cancel -- and, as vferrari noted,
is consistent with the Equinox instruction manual.
But -- I think it is important to note once more, for those who may be a bit uncertain, that noise cancel has NOTHING to do with mitigating "ground noise." The "noise" a detector is hearing from the ground, is of course indicative of GROUND MINERALIZATION, and mineralization being reported by the machine is in NO WAY "mitigated," or "dealt with," via "noise cancel." Ground mineral can ONLY be "mitigated," of course, via ground balancing.
Finally, I would like to note that we do sometimes underestimate the EFFECTS of EMI. "NASA-Tom" Dankowski has an immense amount of knowledge in this area, and he is a HUGE proponent of educating detectorists on just how much of an effect EMI can have, on a detector's ability to find targets on a given day, at a given site. There was a very interesting, recent discussion over at NASA-Tom's forum, on this topic. I won't repeat all of it here, as many would find it tedious and long-winded. However, what I will say is that he recently documented a case where he performed air testing of a dime, at a given site, on different days, and using different noise cancel channels. Some channels were silent, some were noisy, but even some of the channels that were silent were experiencing "silent" EMI -- to the degree that SOME of the "silent" channels produced good depth results on the dime, and some were extremely crippled, in terms of detecting that dime at depth.
I will post a short "snippet" of one of his posts describing this testing, in quotes, below. I find this FASCINATING...
"I tested EQX in Prospecting Mode-2 ...at one of my remote test-gardens ...….. with the following air-test results on a clad dime:
Dec. 03 = 12" in Noise Cancel channel -6
Dec. 04 = 10" in Noise Cancel channel -6
Dec. 07 = 13" in Noise Cancel channel -6
No other settings were changed. All parameters were exactly the same. On Dec. 03 and Dec. 07...... absolutely zero audible EMI. On Dec. 04..... I could hear a very slight amount of EMI chatter. Certainly not enough for me to be concerned about. (((Or should I be!!))). Can you see were there's 'significance' in an air-test? Can you see were there's 'significance' in carrying a spare dime.... for a 15 second test?
At this same exact site...…. on Dec 09...…. I encountered the following resultant:
Noise Cancel channel '0' = 10"
Noise Cancel channel '7' = 13"
Soooooooooo………..by virtue of carrying a dime with me in the field...…. and taking 20 seconds to test the best (top two EMI-free) Noise Cancel channels.... in an air-test; subsequently to witness/experience a 10" noise-free channel...… and a 13" noise-free channel...……. do you think I should then proceed to hunt with the 10" channel?
Again...… can you see the importance of carrying a spare dime with you...in the field?"
(the above quote attributed to NASA-Tom Dankowski, Dec. 2018).
Again, I find those results FASCINATING, and they do show that EMI can have DRASTIC effects on detector performance -- from site to site, and from day to day at the same site, and OF COURSE from amongst different noise-cancel channels.
Just some food for thought...
Steve