Are All 800's Created Equal?

[Chase Goldman]

16 hours ago, Raphis said:

That’s not the way the auto noise cancel works on the Equinox.  The machine will scan the entire spectrum of channels (-9 to +9) and select the channel with the least interference.  Maybe your experience when you do a noise cancel with your Nox in “your” detection sites seems to only select 2-5 different channels most of the time, but I can assure you I have seen every noise channel Selected on my Nox....I hunt in urban city parks here in LA, and the EMI changes multiple times depending on where I hunt within most of the parks here....I noise cancel at least 10 times in a 3-4 hr hunt...baseball fields with large pole lights are notorious for EMI.....as are electronic sprinkler systems, and Rec center burglar alarms.

I think what Sinclair may be saying is that you can sit in one spot and run Auto noise cancel several times in a row and it may select several different numbers perhaps only 2 or up to 5 or more.  The reason being that more often than not, EMI is sufficiently low enough such that the Equinox will have a choice of several different quiet channels.  As EMI levels increase, fewer channels will be able to meet the minimum noise threshold.  Could be wrong, but that's how I read it.

[Raphis]

1 hour ago, Chase Goldman said:

I think what Sinclair may be saying is that you can sit in one spot and run Auto noise cancel several times in a row and it may select several different numbers perhaps only 2 or up to 5 or more.  The reason being that more often than not, EMI is sufficiently low enough such that the Equinox will have a choice of several different quiet channels.  As EMI levels increase, fewer channels will be able to meet the minimum noise threshold.  Could be wrong, but that's how I read it.

Hello Chase,

I’m glad you decided to join in on this conversation regarding noise cancelling on the Nox. It’s always better to have multiple viewpoints on subjects.

Per the Nox manual on auto noise cancel:

“Auto Noise Cancel automatically scans and listens to every frequency channel and then selects the one with the least interference.“

So, if we take this as fact, then the Nox software measures and records an EMI level (dB ??) of each channel, then selects the channel with the “lowest“ level of EMI.  Sure, after a scan of frequencies, the software may find multiple channels with low levels of interference, but it will still select a channel with the lowest interference of the 19 channels.  Now,  I’d assume if the lowest interference value recorded from an auto noise cancel initiation just happened to be recorded identically on 2, 3, or 4 channels out of the 19, then the software could select either of those channels with the same lowest interference level.

[Chase Goldman]

16 minutes ago, Raphis said:

I’m glad you decided to join in on this conversation regarding noise cancelling on the Nox. It’s always better to have multiple viewpoints on subjects.

Per the Nox manual on auto noise cancel:

“Auto Noise Cancel automatically scans and listens to every frequency channel and then selects the one with the least interference.“

So, if we take this as fact, then the Nox software measures an EMI threshold level (dB ??) of each channel, then selects the channel with the “lowest“ level of EMI.  Sure, after a scan of frequencies, the software may find multiple channels with low levels of interference, but it will still select a channel with the lowest interference of the 19 channels.  Now,  I’d assume if the lowest interference value recorded from an auto noise cancel initiation just happened to be recorded identically on 2, 3, or 4 channels out of the 19, then the software could select either of those channels with the same lowest interference level.

Funny the manual is being quoted to me for a change when I am usually the one doing the quoting.  Lol.  I like it when people do their homework.  So that is refreshing.  But that is a given, because I know you really know your way around the Equinox and have provided great insights and tips on this forum as well as the field success to prove it.  So my statement is not meant as a knock but as an acknowledgment of your detecting and, especially Equinox, expertise.  In other words, respect.

Anyway, I am familiar with what the manual says and believe the Equinox noise cancel algorithm is indeed picking the channel it thinks has the least interference at that time.  But when the site is quiet, like I said, many channels may indeed vie for the "least" interference channel crown.  But it is not that the channels are "identically" or "equivalently" least noisy.  In fact, it is unlikely that is ever really the case.  The reason being twofold.  First, when noise levels are low, it only takes small field perturbations to cause channels to pop out of the muck and be considered noisy (this depends on the sensitivity of the EMI signal detection circuit (basically a radio receiver) the Equinox uses - I have no idea how they have implemented that.)  Second, since these perturbations vary with both TIME and FREQUENCY (think Equinox "channel") and since the Equinox is not scanning all the channels simultaneously, it stands to reason that on the first pass, Channel X will win the "least interference" crown and on the second pass, Channel Y will win the "least interference" crown, etc.  Run it 20 times under quiet conditions and you may get most of the available channels to pop up as the selected "least" channel simply due to the randomness not of the Equinox, but of the low level EMI noise signal present.  If it is truly a random selection from a "normal" distriubtion of noise frequencies, then you might see specific channels repeatedly picking up over others. But in the end, when the EMI is low, it probably really doesn't matter what channel is chosen.  As a matter of fact, you can probably be lazy and not even do a noise cancel with minimal chance of affecting your detecting session.

GB Amateur did a series of tests with noise cancel and documented them in his EMI Frustration thread here to try to determine the likely channel outcome distribution here.  I think he may have been picking up on the phenomenon I describe above, where any of several channels can be chosen as the quietest channel but the only a few consistently show up as the quietest channel upon repeated scans.

However, under heavy EMI conditions, especially if the EMI is broadband (i.e., affecting multiple Equinox channels) or is coming from multiple sources (think of multiple of WiFi routers), then the number of possible quiet channels may be significantly reduced.  But if you are moving around under those conditions the quiet channel solution CAN change drastically as you move nearer or further from the source or if the source signal changes in intensity or frequency or with time, or as is frequently the case, there are multiple significant EMI sources.  Hence, frequent noise cancelling during the hunt is called for.  This is especially true when two Equinoxes are in close proximity because they tend to pick up each other (and why some clubs are banning Equinox's from being run in Multi during croweded contest hunts because they zap everyone else around them with broadband noise. )

[GB_Amateur]

Here's a thread from a couple years ago where I show the result of an experiment in my backyard (which is pretty EMI noisy being close to houses, especially mine!).

I think the 1/19 assumes independence of the two detectors' Noise Cancel channels.  IMO that's hard to justify/prove, but I find the argument/disagreement over whether the probability of being on the same channel is 1/19 or some larger number a bit esoteric.

But sometimes I like esoteric discussions.  😁  So here's a thought experiment:  suppose you could query every Equinox 600 and 800 to find which Noise Cancel channel is currently selected.  Is there a channel that would get more votes than the others?  (Hint: answer is easy, as is the proof.)

[midalake]

Just now, GB_Amateur said:

Here's a thread from a couple years ago where I show the result of an experiment in my backyard (which is pretty EMI noisy being close to houses, especially mine!).

I think the 1/19 assumes independence of the two detectors' Noise Cancel channels.  IMO that's hard to justify/prove, but I find the argument/disagreement esoteric.

I think it was installed by Minelab as a roulette wheel to keep us busy while detecting.  🤣   After all standing in one location I can place my bet and my number never comes up!!!!! Just like in the Casino. 🤣

[GB_Amateur]

10 minutes ago, Chase Goldman said:

I... believe the Equinox noise cancel algorithm is indeed picking the channel it thinks has the least interference at that time.  But when the site is quiet, like I said, many channels may indeed vie for the "least" interference channel crown.

Yes, and you linked to my experimental results about 30 seconds before my post (with that link) made it to the site.  I guess you have a faster internet connection. 

Regarding the above quote, it's my view/experience (at least in my area) that either a site has low EMI in which case many channels will satisfy, or the EMI is so high that none solve the problem.  However, there have been instances where I was getting slammed by noise in one channel and a Noise Cancel procedure quieted it almost perfectly.  That's the ideal case and one we all prefer.

My knowledge of these noise sources is quite limited, but I suspect that broad band sources are the ones we cannot eliminate whereas narrow band sources are the ones where the NC procedure really shines.  (And reading Chase's most recent thread above more carefully, that seems to be consistent with what he said in the last paragraph.)

[Raphis]

1 hour ago, GB_Amateur said:

I think the 1/19 assumes independence of the two detectors' Noise Cancel channels.  IMO that's hard to justify/prove

You’re probably right, GB.  Based on your experimentation on this subject and Chase’s reliable, insightful contributions, even though there are only 19 noise channels, and the Nox will choose one of those 19 noise channels as “the quietest” channel after completion of an auto noise cancel, that doesn’t necessarily mean there’s gonna be a 1/19 probability that your machine will select the same channel as your hunt buddy’s, who’s hunting with you...because of the particular/specific sources of EMI, and also “when“ each person chooses to do an auto noise cancel when hunting together.  In addition, because noise cancel is a local setting, the Nox stores many different noise cancel values in memory (one for each mode, I believe ??...someone correct me if I’m wrong here)

[Chase Goldman]

1 hour ago, GB_Amateur said:

Here's a thread from a couple years ago where I show the result of an experiment in my backyard (which is pretty EMI noisy being close to houses, especially mine!).

Good glad we did simultaneously post it as it saves people from having to plow through my entire verbose post to find the identical link.  You can see it made an impact since I still recalled it.

[Chase Goldman]

23 minutes ago, Raphis said:

In addition, because noise cancel is a local setting, the Nox stores many different noise cancel values in memory (one for each mode, I believe ??...someone correct me if I’m wrong here)

You are correct.  It probably does this to account somewhat for self generated EMI and different input signal processing/filtering associated with each mode.

[nordic]

It's probably correct to assume there are not 19 channels, but 19xFrequencies Nox operates in selected mode.

As you may know, what we call channels are simply frequency offsets from base frequency. Nox operates at multiple frequencies, but offsets (channels) are the same? Say, if Nox worked at 5, 10, 15 khz simultaneously, channel 1 could be 5.1, 10.1, 15.1 khz and so on. What Nox does when 5.1 khz is noise free and 10.1 is full of it is hard to tell...