Minelab Equinox Challenge

[bklein]

I don’t get what you can gain from any more information. It is only the TX side and the magic is likely in the RX and DSP processing. I like the CTX way better for several reasons and am selling my 800. I’ll wait for it’s replacement. My Spectrum Analyzer photos here were likely 1.5fw, btw.

[Mark-VA]

Well since I've fell for all the hype, I'm stuck for the time being. I'd still like to know this?

I must admit I fell for the Multi IQ from the very beginning and it sold me to an extent I had to have one and bought the 800 model right out of the gate.
In subsequent weeks I tested the Equinox side by side with the Fisher F75 LTD and found it extremely hard to get a winner between the two.
But the Equinox was a quieter running machine in hot ground. But that is not exactly the truth, listening very carefully I could still hear the hot ground but at an extremely lower volume. I feel Minelab might have done a little programming magic to reduce the noticeable noise to the end user.


A wealth of information has been published on this site.
Asking for something below:

1. As an overall recap I'd like to see the actual frequencies used in each program, starting with Park 1 all the way through Gold 2.

2. Then the actual frequency if each is chosen as a single frequency, if there is a difference.

[Skippy]

I think we're pretty certain that the single-frequency options are exactly as claimed, and it's unlikely they will change that.

It's the multi-freq details that are looking hard to pin down, now.

[bklein]

Just sold mine so can’t do any more scans...

[Mark-VA]

I would imagine it would be very important to scan while the machine is attached to the coil but I don't know if that is possible.
I feel the coil is an important part of the transmission frequencies.
What do you all do just scan the pins coming out of the control box?

[bklein]

I just put a coil under the detector coil and fed the output to the Analyzer.

[Skippy]

Everyone so far has used some kind of pickup coil, either a simple air-cored coil, such as one salvaged from a junk detector coil, or Carl M. used a coil wound around a ferrite rod, I don't recall the details re: turns, rod size etc. No-one has seen the need to actually intercept the wires from/to the coil.

[Mark-VA]

So you can see what is leaving the coil when it comes to frequencies, voltage, amps and a possible time frame.
This is where the two frequency info posted on the internet came from.
I looked the multi up and the definition is:
"more than one; many, especially variegated."
But Minelab portrayed many frequencies, simultaneously. Led me to believe it was the entire group of frequencies at the same time.

[Skippy]

So you can see what is leaving the coil when it comes to frequencies. Yes.

.. voltage Sort of. If you use an air-cored pickup coil, you are effectively creating a transformer, the voltage on the pickup coil looks essentially the same as that applied to the transmit coil, only at a higher or lower voltage, depending on how many turns each of the coils have, how they are positioned relative to each other, etc.

.. amps. Not directly. You can mathematically calculate Amps by knowing the voltage applied to the coil, combined with the coil inductance. Or, you can use a different type of pickup coil ( one that integrates) to produce a mimic of the actual current, see 'voltage' above.

.. and a possible time frame. Correct.

You were interested in frequencies used, so actual Voltage and Current values are irrelevant.

[dbanner]

This guy use a 2.5mH pickup coil. Spectrum analyzer.
https://m.youtube.com/watch?v=D1GCaNdGUWU

[Mark-VA]

That guy is pretty good. I would really like to know more about the Equinox and its frequencies. The only thing I have is a HP dual scan oscilloscope.

[Carl-NC]

For single freq detectors, a frequency counter is overwhelmingly easier than a spectrum analyzer. I expect his HP has an auto-measure feature, not sure why he doesn't just use that.

---

A voltage-mode magnetic field probe will produce an output that is the derivative of the magnetic field being measured, which should be the same waveform as the voltage driving the TX coil. This is what you don't want. What you do want is to measure the actual magnetic field waveform. You can do this with a current-mode probe:



The feedback resistor depends on the probe wire resistance but a few hundred ohms up to ~1k is proper. The opamp should have a fair amount of GBW product depending on the highest freq of interest. I tend to shoot for 100kHz or more, so I look for a GBW > 10MHz. You may need a little bit of feedback C for stability, keep it as low as possible. This is a super-simple circuit that heavily depends on the probe design so expect to futz with it a bit.

[Skippy]

Marks HP 'scope should be adequate enough to compare his machines TX waveforms with those shown by Chiv, BKlein, Carl. If he still has the original V1.5 firmware, I expect he will see the same waveforms. Which showed:
Park1,2, Field1,2, Gold1,2 were all 7.8k + 18.2k + 39k
Beach1,2 was 7.8k + 13k + 18.2k + 39k

I don't know how many upgrades there have been, Mark should know, the only one I know of is 1.7.5. But re-load it with the latest firmware, and Mark should see what's different. Maybe even something matching Carls measured outputs.
Carl: I assume you have the latest firmware in your 'test Nox' ?

[Mark-VA]

Scope

This is my scope. I bought this many years ago when I used to repair computer monitors but never did use it. It was purchased from an old man who ran a TV repair shop for many decades. I learned a lot from him but actually I've never used this scope and have no idea where to start. But I have the original manual. It's funny how that repair business vanished as quickly as it appeared.

[dbanner]

The service manual for your HP 1220A oscilloscope is available for download online. Maybe good idea to go through recalibration procedure first, just to get her back in the zone. A machine with that age, good idea to have a look at the caps and such, overall service etc. Avoiding magic smoke after long layoff.
HP is top notch machine any day.