Not Much Chat About Multi Frequencies

[Gwcracker]

Your faith in MF is greatly appreciated... apparently. Someone needs to ask the smart one, XPCalabash, SSDD.

😉

[shopkins1994]

1 hour ago, Gwcracker said:

Your faith in MF is greatly appreciated... apparently. Someone needs to ask the smart one, XPCalabash, SSDD.

😉

They don't know how to use a detector. They swing their detectors like it's one from 1975. Check out my Hecks Yeah! YouTube for real info on detectors. 

[Gwcracker]

Very interesting, Thanks!

[PimentoUK]

So, here's my frequency analysis post resurrected, plus an additional Youtube video on the topic:

A poster on the Geotech1 forum found this Youtube video, showing a 'scope examination of the coil drive voltage:

https://www.youtube.com/watch?v=E2AYJp2uH2U

It's not really worth watching, it's dull and nerdy, and in Russian or Ukranian, I just included it so you know I'm not making stuff up ...

So it's broadly similar to the Equinox / DFX , forcing complex square-edged signals onto the transmit coil.
I have no idea what Mr. Youtuber is saying, so I just observed what was shown, and interpreted it from an engineers view.
The modes:
P1 : General
P2 : Sensitive
P3 : Sens FT
P4 : Fast
P8 : GoldField
P12 : Beach; all run at 8.08 kHz & 40.4 kHz, a 1:5 ratio.
-----
P5 : Park
P9 : Relic
P11 : Beach; all run 8.08 kHz & 24.24 kHz, a 1:3 ratio.
-----
P6 : Deep HC
P10 : Dive; both run 4.76 kHz & 14.3 Khz, a 1:3 ratio ( not unlike the Fisher CZ range, but a different waveform shape )
-----
P7 : Mono, does what you'd expect, a single freq square-wave, just like the Equinox.

It looks like P6 / P10 run a three-level waveform, possibly to reduce power consumption, obviously important for a coil with a small internal battery.

How they process the freqs is of course the important bit. It's probably safe to say the GoldField mode is going to emphasise the 40 kHz. And the Deep HC will be using the 4.76 kHz as it's dominant one, to target the milled copper/silver coins.

Another Youtube video on the subject:

https://www.youtube.com/watch?v=0QgAVNWaDD4 

 

 

 

[Chase Goldman]

 

1 hour ago, PimentoUK said:

So, here's my frequency analysis post resurrected, plus an additional Youtube video on the topic:

A poster on the Geotech1 forum found this Youtube video, showing a 'scope examination of the coil drive voltage:

https://www.youtube.com/watch?v=E2AYJp2uH2U

It's not really worth watching, it's dull and nerdy, and in Russian or Ukranian, I just included it so you know I'm not making stuff up ...

So it's broadly similar to the Equinox / DFX , forcing complex square-edged signals onto the transmit coil.
I have no idea what Mr. Youtuber is saying, so I just observed what was shown, and interpreted it from an engineers view.
The modes:
P1 : General
P2 : Sensitive
P3 : Sens FT
P4 : Fast
P8 : GoldField
P12 : Beach; all run at 8.08 kHz & 40.4 kHz, a 1:5 ratio.
-----
P5 : Park
P9 : Relic
P11 : Beach; all run 8.08 kHz & 24.24 kHz, a 1:3 ratio.
-----
P6 : Deep HC
P10 : Dive; both run 4.76 kHz & 14.3 Khz, a 1:3 ratio ( not unlike the Fisher CZ range, but a different waveform shape )
-----
P7 : Mono, does what you'd expect, a single freq square-wave, just like the Equinox.

It looks like P6 / P10 run a three-level waveform, possibly to reduce power consumption, obviously important for a coil with a small internal battery.

How they process the freqs is of course the important bit. It's probably safe to say the GoldField mode is going to emphasise the 40 kHz. And the Deep HC will be using the 4.76 kHz as it's dominant one, to target the milled copper/silver coins.

Another Youtube video on the subject:

https://www.youtube.com/watch?v=0QgAVNWaDD4 

 

 

 

Excellent Post!  Very enlightening. 

I now know why Deep HC behaves differently than the other modes, it's a combo of the different lower endpoint and the waveform combined with whatever signal processing algorithm differences XP implements in the algorithm secret sauce for that program.  Besides that, XP also sprinkles clues into their program descriptions that throw out seemingly descriptive but still vague (or unexplained terms) like "Conductive Soil subtraction" (Prg 1 and 10 - 12), "Frequency addition" (Prg 2 -6, & 8), and "Frequency Subtraction" (Prg 9).  These make me wonder what is really going on under the hood when you compare programs on paper.  For example, the only apparent difference between General (P1) and Sensitive (P2) [not accounting for the slight difference in user settings (Disc 7 vs. Disc 6.8, No Notch in P1 vs. a programmed Notch 1 in P2, and Audio Response 4  vs. 5) is "Conductive soil subtraction" vs. "Frequency Addition".  If set up identically, would they behave differently on some specific target?  Who knows.  I'm not one to meticulously test any and all possibilities because frankly it bores me to death both doing it and watching/reading about it and I really just want to hit the sites to detect when I can.  I will figure out a way to delve into this, somehow, and try to answer my own rhetorical question.

Deep HC and Dive still suck the juice out the coil more than any of the other programs so imagine what the coil power consumption would be if they weren't trying to manage it with a multi-level waveform.

[PimentoUK]

Yes, the lower freq mix of 'deep-HC' ( compared to the other modes, or compared to the Eqx 7.8k/18.2k/39k mix ) is what could give the edge when hunting high-conductor targets. And It's something I've postulated ( in other threads ) ML could implement on the Eqx ... but it's possibly been tried and is not significantly different, or it raises other issues, like the coil being 'not so hot' at the lower limit of its range.

Power consumption is higher for low frequencies because the impedance of an inductor ( the TX coil ) falls as driven frequency falls, in direct proportion. And low impedance means higher current flow, basic electronics maths. Unless you take steps to counteract it, such as reducing drive voltage, like XP have done.

However, I did a lot of analysis of the waveform over on Geotech1, and there's another possible reason:
If you add sine-waves of f and 3f together, with similar amplitudes, you get a resulting waveform that closely resembles the D2's 'deep-HC' signal. This multi-level signal may offer techy benefits... one possibility is: obtaining a faster response could be easier if the demodulated waveform is 'cleaner', being more sinusoidal than those produced by the 8/24k modes, for example.

[Chase Goldman]

Deep HC to me just seems to be more responsive overall and seems to do better than the other modes in thick iron (I have not used the beach modes/Dive) and so this may correspond to your f and 3f processing speculation.

[PimentoUK]

Taken from a D2 thread on Geotech1:
Here is what you get adding f and 3f sinewaves, with about 20% more amplitude on the 3f wave:

[below]

Now square it up, and there's the Deep-HC waveform.

PWM-type f/3f waveforms don't at all resemble two sine-waves added together. Neither does a simple f square-wave ( eg. Fisher CZ ), which also suffers from a much lower 3f amplitude ( about 1/3rd the fundamental ), which can give noise-related issues.

 

 

[Welwood470]

On 4/24/2022 at 11:18 AM, PimentoUK said:

I have no idea what Mr. Youtuber is saying,

You do know you can use closed captions and auto-translate? I used

it and still didn't understand a lot of the technical part.🥺

[PimentoUK]

My PC is not a super up-to-date one, that kind of stuff probably won't work. Pretty soon, it will fail to handle YouTube completely, I regularly get warnings about it.