Minelab Equinox Challenge

[Skippy]

Have you tried a lower 'bit depth' ? 16 bits is more than enough, maybe then you can achieve higher sample rates, or longer sample lengths?

[EL NINO]

I just try to measure it, but I'm afraid I'm already in the limit, my laptop has more than 10 years...

[EL NINO]

Have you tried a lower 'bit depth' ? 16 bits is more than enough, maybe then you can achieve higher sample rates, or longer sample lengths?

Thanks for your help - I set it up to 16bit and it works well ..in max...


But it's still not perfect, -the scanner is within Equinox frequency limits - I'll have to buy a better sound card -192 / 24bit ... Limited range spectrum at 65K FFT and full spektrum at 32k FFT

[Mark-VA]

I finally had a try at it and here is what I see.
Strange what park1 frequency 5 shows.

[Mark-VA]

Multi frequency looks like this.
Wow, I'm having a blast but have a lot to learn

Thanks El NINO

[EL NINO]

Do you have 192kHz sample rate as an option, Nino ?
Do you think it will make any real difference to the spectrum analysis ? At 96k sample/sec, he's (just) sampling more than two samples per cycle of the highest freq of interest, 40kHz.

I found out that in my 2 laptop I have a better sound card working on 192/24 bit, so I will make new measurements Equinox ..

[Mark-VA]

On other websites I've been told that using the frequency spectrum is the absolute wrong approach.
So.
I'm after one thing, what is the main transmit frequency of each option on the Equinox.
Park 1, Multi frequency, frequency 5, 10, 15, 20, 40.
By what I see on my post the 10, 15, 20 are dead on, 5 gives odd results.
So, why is the frequency spectrum the wrong thing to look at.
If it is, what should my approach be?

[Skippy]

Version 1.5 ( original release ) actually operated at 5 kHz when you selected it, as you can see by reading the two Nox threads.
It looks like your firmware ( V1.7.5 ? ) is running at 7.8 kHz when '5k' is selected. Why? Only ML know, really. Maybe testers reported problems at the low 5K freq, such as an easily overloaded coil, or a general lack of sensitivity, and they increased it to a freq they know is good, as it's one of the multi-freq components. I suspect the coil is the most likely issue. Making a coil work well from 5kHz up to 40 kHz is not that easy. The stock coil may be fine, but what about the optional ones, like the large coil ?

As regards " what is the main frequency", that's impossible to answer. We can only look at what the machine transmits. We have no idea what it does with those signals when it has received them. It's perfectly possible to transmit 3 freqs, but only process/use two of them, and ignore the third, for example. The two 'gold' modes presumably give most emphasis to the 39k and 18.2k , and use the 7.8k for some 'ground elimination'. But 'park' will no doubt be set up to be good on copper/silver milled coins, because that's what the Yanks hunt for in parks - they don't consider 5c coins as coins. So 7.8k will be dominant, with varying amount of 18.2k to bring in some sensitivity to 5c's and gold jewellery.
All of that is just educated guesswork, it would be very hard to do more.

[EL NINO]

Equinox on Firmware 1.7.5 Works on 1f-5khz in Park and Field programs perfectly fine ..- even the TX signal is not as high as the other frequency ...measured in one settings,-one time...: 15X12" coil...
5K
10k
15K
20K
40K
Multi

[Mark-VA]

Wow, looks like you have it now. I'm still trying to use the frequency spectrum analysis. I need to confirm that the frequencies it is showing on Equinox are correct and by your information I'm getting the same thing only in a different form.
I have a couple Fisher detectors I can test tonight.

[EL NINO]

I keep it clear from Equinox 1.7.5 -in multi .f, change Tx frequency gain by program Gold2 = Park1, Gold1 = Park2, Field1 = Field2, Beach1 and Beach2 programs are different .. Whites Spectra V3 has TX on all programs equally ... even in 3F salt ... I try to compare the Equinox 1.7.5programs to old f1.5.0 ..,,

[Mark-VA]

Well I've discovered something. I've got the program set and each of my screen shots look very similar including the frequencies.
But frequency 40 will not come up. I went through each of the programs and changed the frequency to 40 and none, even the gold programs would indicate 40 was present, but rather the frequency 5 was what came up when choosing 40.

Not sure what this is all about, but when choosing frequency 40 indicates something is wrong.
I'll try and revert to the previous version before I updated the Equinox last fall and see if there is a difference.
Looking at the wave form of 40 and 5, they just don't match.

I also did a screen shot of my Fisher F75 and the frequency is dead on.

[Mark-VA]

Thank you EL NINO, for the solution to my problem

Mark, I see the Park1-Multi picture, you have already captured the 40 kHz frequency, and the "Recalibration" bandwidth on the spectrum analyzer is using the log-X-axis function. To increase or decrease the signal level, use Log and the slider on Y -axis ... it's simple ...

[Sean_Goddard]

WELL, WELL, what do you know, a COMPOSITE WAVEFORM, just like the one in the spec I posted on here in the MF section two years ago and which I sent to Garrett 20+ years ago. Garrett released the 2500 GTi (as opposed to the "Digidec GTi" which was MY proposed name for it) about 18 months AFTER they had sight of my document. Make of that what you will, but some of the 2500's features definitely came from my document, and Garrett COULDN'T prove that they had been working on something similar when challenged.

The words "Told you so" spring to mind.

[dbanner]

WELL, WELL, what do you know, a COMPOSITE WAVEFORM, just like the one in the spec I posted on here in the MF section two years ago and which I sent to Garrett 20+ years ago. Garrett released the 2500 GTi (as opposed to the "Digidec GTi" which was MY proposed name for it) about 18 months AFTER they had sight of my document. Make of that what you will, but some of the 2500's features definitely came from my document, and Garrett COULDN'T prove that they had been working on something similar when challenged.

The words "Told you so" spring to mind.

Curious to say the least. By the way, that VA software is remarkable, having a blast playing with it. When I click on DAC box, some magic happens which gives me smooth sinus at 14.5 khz(tgs). The spectrum analyser is really cool. And the thing runs in Linux under Wine. Fantastic.