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Five Frequency Times Eight


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5F×8 (used in EQUINOX 800*)

 5F×8 (Five Frequency Times Eight) provides five individual transmit frequencies in the one metal detector, selectable at the push of a button. Each transmit frequency optimises the detector for different size targets and conditions. EQUINOX 800 offers 5 single frequencies of 5, 10,15, 20, and 40 kHz, giving an 8 times range or ratio from 5 to 40, hence the 5F×8 technology designation.

The individual selectable frequencies in EQUINOX 800 are:

  • 5 kHz - Great for large silver coins
  • 10 kHz - Good for small Roman hammered coins
  • 15 kHz - A good general treasure detecting mode
  • 20 kHz - Ideal for general treasure detecting and gold prospecting
  • 40 kHz - Optimum sensitivity to very small gold nuggets

Having five selectable frequencies gives the versatility that is equivalent to five conventional single frequency detectors.

Note that EQUINOX Series detectors also feature Multi-IQ technology which allows you to operate all available single frequencies plus more, simultaneously. The option to operate your detector in a single frequency can be helpful if you are experiencing excessive ground noise when using the Multi-Frequency setting.

*The Equinox 600 3F×3 (Three Frequency Times Three) offers three single frequencies of 5, 10, and 15 kHz, giving a 3 times range or ratio from 5 to 15, hence the 3F×3 technology designation. However, both the Equinox 600 and Equinox 800 offer identical Multi-IQ modes covering the full frequency range. The Equinox 600 simply disallows direct access to the 20 khz and 40 kHz single frequency modes.

More on selectable frequency and frequency spread here.

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So when you say the 600 disallows access to the top two frequencies is this something in the reading material?  :{)  Are the goodies in the box waiting for curious fingers to turn on.....

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From http://www.detectorprospector.com/forum/topic/4488-minelab-equinox-multi-iq-technology-part-2/

minelab-equinox-multi-iq-metal-detector-technology-frequency-response-chart.jpg

“* 20 kHz and 40 kHz are not available as single operating frequencies in EQUINOX 600. The Multi-IQ frequency range shown applies to both EQUINOX 600 and 800. This diagram is representative only. Actual sensitivity levels will depend upon target types and sizes, ground conditions and detector settings.“

Access to the Gold Mode and therefore the 20 kHz and 40 kHz single frequencies is limited to the Equinox 800.

Gold Detecting Mode - Gold Mode operates the high single frequencies of either 20 kHz or 40 kHz to detect gold nuggets in mineralised soils.”

minelab-equinox-600-800-specifications.jpg

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3 hours ago, Steve Herschbach said:

Gold Mode operates the high single frequencies of either 20 kHz or 40 kHz to detect gold nuggets in mineralised soils.”

While perhaps not quite up to the GM1000 in sensitivity to the smallest nuggets I'd bet it will be a real blow to the rest of the competition.

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Thanks for that Steve.  I'd read it but it didn't click.  So I reckon it wont be long till there is a hack.... well a few years maybe if you like your warranty ;) and have a couple of grand to break things with. Hahh.  I was excited and well pleased with the new tech of the Zed so I am keeping an eye on this as my old DFX is a bit long in the tooth for a multi freq park sniper.

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Detector manufacturers often make one main board for manufacturing volume and efficiency. The top model has all the features activated. Less expensive models they simply limit access to some features, but it is the same detector under the hood. For instance, a White's VX3 is the same circuit board as a V3i with a few features turned off. However, it is not a matter of going in and flipping a switch - the limitations are usually encoded in the firmware. A basic $499 Fisher Gold Bug is the same as a Gold Bug Pro internally. They just took away your access to the manual ground balance. Everyone does it and not just in the detector industry.

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  • 4 years later...
On 11/15/2017 at 9:26 AM, Steve Herschbach said:

From http://www.detectorprospector.com/forum/topic/4488-minelab-equinox-multi-iq-technology-part-2/

minelab-equinox-multi-iq-metal-detector-technology-frequency-response-chart.jpg

“* 20 kHz and 40 kHz are not available as single operating frequencies in EQUINOX 600. The Multi-IQ frequency range shown applies to both EQUINOX 600 and 800. This diagram is representative only. Actual sensitivity levels will depend upon target types and sizes, ground conditions and detector settings.“

Access to the Gold Mode and therefore the 20 kHz and 40 kHz single frequencies is limited to the Equinox 800.

Gold Detecting Mode - Gold Mode operates the high single frequencies of either 20 kHz or 40 kHz to detect gold nuggets in mineralised soils.”

minelab-equinox-600-800-specifications.jpg

In another thread I mentioned my interest in the -3db Half-Power Level. I noticed it was discussed in one of the articles on this site (written by Andy I think).

I have used ‘half power’ points many times in electronic subjects dealing with analog audio signals, eg., audio amplifiers as typically used in studio settings.

Anyways, generally quoting a few statements that grabbed my eyes:

‘For -3db frequencies. . . 
Examples given: a dime and a penny -3db freq is ~2.7kHz. Silver dollar -3db is ~800Hz. Nickles ~17kHz. Thin rings and fine gold are usually higher still.x
These results are based on a VLF detector with max Sensitivity and positioning the transmit frequency directly on the target’s -3db frequency point.’

I often asked my self, what is the better single frequency for a given target? I suspected something like this but . . . the catch is someone has to determine each target’s ideal center frequency, ie., I think of it as the target’s center of gravity if you will.

Please expand on this topic.

Thanks, Billy
 

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The target can be modelled as a simple first-order low-pass filter, but rather than the familiar R-C components, it's an L-R circuit. The -3 dB freq is the freq at which the phase lag is 45 degrees.
If you measure the target at another freq, you will get a different phase lag, which can be measured. Mathematics will then allow you to calculate the target's -3 dB frequency.
However .... targets can have and do have frequency-sensitive characteristics. This is due to induced circulating currents not penetrating deeply into the target ( skin effect ). As a result, bulky, thick targets will behave slightly different at different freqs. Low test freqs will see more of the skin than a high test freq. So to get the best target freq measurement, you should use a test freq close to that of the target, maybe +/- 30%. Measuring a 1kHz target at 18 kHz is likely to include some target-dependant error.

Probably the simplest way of measuring a target's frequency is to use a good target ID detector, which you have calibrated the scale. The Fisher F75 is pretty good for this, having a large non-ferrous range. All you then do is wave the target over the coil, read the ID, and look up on your calibration chart/table to see the -3 dB freq.

Also: determining what is the best detector freq to use for a given buried target is another more complex problem. Detectors also measure the ground: a higher detector freq give stronger ground pickup, which compromises its ability to distinguish the target from the ground.
So that's one plausible reason why a detector operating below the desired target freq is best. But there are arguments going the other way ( I forget what ... ) suggesting a higher detector freq is optimal. In practice, it doesn't seem to be too critical, thankfully.

You can manufacture dummy targets from loops of wire. By calculating the loop resistance, R, and loop inductance, L, you can calculate the -3 dB freq

w = 2 * pi * f = R / L

As a result of some target-modelling tinkering we did on the Geotech1 forum, I have a dozen or so of these targets, made from copper wire. Theory and practice agree well, for PI and VLF machines.

CuRing2_7304.jpg

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I agree of course.

I was relating to the -3db frequency point of a given target (assuming all other being equal, e.g., shape, orientation, size, conduction value, etc. ). As I understand it, the target's reflected signal is maximum at the ~ -3db frequency level. This is assuming the transmitted frequency is also set to the target's frequency -3db level point. This happens to be the r-component of the signal, which is defined at it's  half-power point.

For example, with everything being equal, a given target has an optimum single frequency, yielding maximum reflected r-signal level to be analyzed. I would tend to think this has a lot to do with Multi-IQ design and resulting algorisms. 

Anyone expand on this? Am i somewhat correct on this?

Thanks, Billy

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Getting complicated, now.

Detectors don't just measure the reactive component of a target. If they did, a 13kHz machine ( decent all-rounder Fisher F75, for example ) would be hopeless at finding 1 kHz targets ( US silver dollars / half-dollars ), as the phase lag is about 86 degrees, with the reactive component way less ( 7% ) than the resistive component.

"I would tend to think this has a lot to do with Multi-IQ design and resulting algorithms"

Now you're bringing multiple freqs into it ... and it sounds like you don't really understand the why's of multi-freq.

Using multiple frequencies has very little to do with "hitting the target with a range of freqs hoping that one will hit the spot". It's primarily about working out the ground signal, so it can be largely eliminated, thus making the target more visible.

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