What Difference Does 1khz Have On The Equinox From 5khz To 4khz?

[phrunt]

Our smart power meters in NZ send data via the mobile phone network wirelessly from the home meter to the supplier.  We also have Ripple Control which is used to switch older meters from day rate to night rate and for controlling load in heavy load situations turning off things like hot water heaters but this wouldn't mess with a detector.

Ripple control is the most common form of load management, and is used in many countries worldwide. It works by superimposing a high frequency signal, usually between 100 and 1600Hz onto the standard 50-60 Hz main power signal

You can of course send data over power cables such as the home kits for Ethernet over Power, they are really cool as you don't need to run Ethernet cables around your house, just use the power wires to transmit the data, as long as they're on the same circuit it's all good so I can imagine there is larger scale versions of that outside of your house that they can use to transmit data over the actual power lines but haven't heard of anything that does it.

My understanding is for things like in home automation and Ethernet over Power sit in the range of 20 to 100kHz, so more likely to affect the higher frequency detectors and with a small range so you would need to be right near the house using it. 

 

[Digalicious]

4 hours ago, Chase Goldman said:

 Dig, I know you are not going to take my word for it and will want video proof. 

Not necessarily.

Under certain circumstances, I'm all good with anecdotal evidence, and will forego my usual need for empirical evidence. However, when it comes to metal detecting videos and comparisons, I've seen so much appalling methodology, that often the empirical video evidence, is actually less worthy than anecdotal evidence from a trusted source. With that said, I would consider you a trusted source. So, thanks for taking the time to do the test.

With that out of the way, let's be clear on what we're discussing. Are we discussing something about 4 khz having some magical EMI resistance ability when compared to 5 khz? If so, that's total nonsense and I want no part of that discussion. Granted, there could be an unusual and rare circumstance in which that could be true. I mentioned that previously with an example of a particular device emitting a strong field at a particular frequency. In Steve's thread that you posted, he mentions such a circumstance with a LED light giving off copious amounts of EMI at 19 khz, that was driving his 19 khz detector nuts. In that case, I could see even a shift to just 20 khz reducing the EMI noise. Although if the EMI field is strong enough, then the emitted 19khz might bleed into the adjacent frequencies.

OR...

Are we discussing the possible performance loss when EMI filtering is engaged? Yes, we seem to be discussing this, but the discussion also seems to be getting clouded with both those things. 

Lastly, I don't believe that in its current state, EMI noise reduction can be accomplished without a sacrifice in some other aspect. It doesn't by necessity mean a gain drop, as I've often said, "A performance hit in one way or another". Effective EMI noise reduction would consist of some really aggressive filters, and it's a given that filters subdue something else. 

One last lastly thing lol:

To be clear, was 4 khz quiet even before you noise cancelled, or did you have to noise cancel for 4 khz to be quiet? I ask because I'm wondering if that unique noise reduction algorithm in 4 khz is engaged as soon as you switch to 4 khz, or if it's engaged only when the noise cancel itself is engaged.







 

[Digalicious]

30 minutes ago, BigSkyGuy said:

At the risk of stirring a hornets nest I will throw in my theory as to why 5 kHz is a problem but not 4 kHz. Power lines seem to be a big source of EMI, yet the transmission frequency, as Jeff mentions, is 60 Hz, two orders of magnitude lower than metals detectors. However, I have read that there is a power line carrier communication (PLCC) signal that is transmitted along with the power that is transmitted in the kHz range to as low as 5kH. This is why meter readers are no longer required. The power useage in your home is sent via PLCC. PLCC is also used for home security systems, and home control and automation.

I have used my DetectorPro UW, which operates at 2.4kHz, no problem right under power lines.

Thanks for that info.

That could very well be another example of how a 1 khz change under a specific circumstance, can mitigate EMI. 

[Skyshark]

If anyone was curious, MineLab's response on the 4khz add was a very simple one:

"

The 4kHz single frequency option was added as we had a large number of customers in South East Asia that were trying to detect large stacks of silver coins (stacks of silver coins are buried all throughout S.E Asia)

Each metal is reactive at a particular frequency, stacks of silver coins are very reactive at 4kHz which is why we added this as an option for customers.

If there were stack of silver coins (or large amounts of silver) buried deep in other places in the world the 4kHz single frequency option would be the best single frequency to use.

"

[phrunt]

As expected and I kept trying to say, nothing magical about the 4kHz with EMI, it's just a frequency that shifts enough away from an EMI source for many, no tricks, no magic, no funky new code to try eliminate EMI in a testing phase for a new model...  

Thanks for asking the question and the answer makes complete sense.   Good on Minelab for a simple honest answer and also for adding the frequency to benefit those looking for these targets.

China does have some mega hoards of coins stashed away 🙂

https://www.globaltimes.cn/page/202212/1280957.shtml

An ancient coin hoard containing 1.5 tonnes of coins dating back to the Tang (618-907) and Song (960-1279) dynasties has been discovered in east China's Jiangsu Province.

I'd like to find something like that as a silver coin hoard!!!

[Digalicious]

7 hours ago, Skyshark said:

If anyone was curious, MineLab's response on the 4khz add was a very simple one:

"

The 4kHz single frequency option was added as we had a large number of customers in South East Asia that were trying to detect large stacks of silver coins (stacks of silver coins are buried all throughout S.E Asia)

 

You win the internet today! 🙂

No new noise reduction in 4 khz? That has to be the true answer, because there is no current way that an effective noise reduction algorithm wouldn't cause significant performance degradation. That degradation would normally be in depth loss, but Chase's test showed no depth loss. That's when I knew something wasn't adding up, but I couldn't figure it out.

What has really surprised me though, is how under certain circumstances, 4khz is dead quite, but 5 khz can be very EMI noisy. I guess I just don't have those circumstances, because no matter where I go, 4 khz is never quieter in EMI noise, compared to 10, 15, 20, and 40 khz. Although in most cases, even 10 and 15 is still not quiet. It's not until at least 20 khz, that I begin to get outside the EMI noise range.

[phrunt]

5 hours ago, Digalicious said:

What has really surprised me though, is how under certain circumstances, 4khz is dead quite, but 5 khz can be very EMI noisy. I guess I just don't have those circumstances, because no matter where I go, 4 khz is never quieter in EMI noise, compared to 10, 15, 20, and 40 khz. Although in most cases, even 10 and 15 is still not quiet. It's not until at least 20 khz, that I begin to get outside the EMI noise range.

You must just live in a crazy EMI area, in a few generations the children may start to be born with a 3rd eyeball. 🙂

 

[Digalicious]

3 hours ago, phrunt said:

You must just live in a crazy EMI area, in a few generations the children may start to be born with a 3rd eyeball. 🙂

 

By the looks of some people in my downtown area, it's only going to be a few years!

I'm in a rapidly growing city in North America. All the other hunters I've discussed this with, or read about, also experience that the lower the frequencies, the more EMI noise. It's only been very recently that I've read about some saying the opposite.