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Rx And Tr Questions


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Hello.

I don't plan on purchasing a Manticore, but I still like to learn about the new detectors. With that said, I have two questions about the Manti:

1) Isn't Tr power regulated, and haven't detectors reached the maximum allowed power output a long time ago? If so, what does the Manti's "More power" even mean? Could it be that it doesn't transmit any more than the regulated power at any given time, but rather, each sequential frequency pulse is transmitted at full power? For example, in a SMF mode, both or more frequencies are all transmitted at full power, instead of 1 or more of those frequencies transmitted at low power?

2) If you own a Manti, what sensitivity level can you usually run at without noise, and how often are you able to get even close to 35?

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Dig,

  I have no idea about your first question but in the 5 hours I’ve been able to use mine, I generally have to keep it around 21 Sens in my area.  However, I went to our local freshwater beach the other day, I was able to run a sens of 28, using NASA Tom’s long press noise cancel technique.  

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  • The title was changed to Rx And Tr Questions

No idea on number one.

At the beach I'm running my sensitivity at 22. At the local parks I've been to, anywhere from 20 to 25 depending on EMI. Have not been out in the sticks yet but I would guess with the mineralization we have around here I'll still be limited to about 25.

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The limit on transmit power is physics, not the law. Boosting TX has diminishing returns for increased battery consumption, and in bad ground it just blows back on the detector. Best example is Equinox Beach Mode 2 automatically lowering TX so the detector can function in the worst stuff.

Whether the power is spread though the frequencies or each frequency is running at full power just depends on the design, and I don’t know what’s going on exactly with Manti. It’s kind of moot really. All that matters is how it actually performs versus the competition. Quoting Carl Moreland at the link below:

'"Mathematically, a 50% increase in drive voltage will produce a 7% increase in depth. This assumes far-field. Very close and very tiny targets can show a bigger impact.”

I'd add further that 7% is best case, and much likely to be less once the ground is accounted for.

 

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51 minutes ago, Steve Herschbach said:

The limit on transmit power is physics, not the law. Boosting TX has diminishing returns for increased battery consumption, and in bad ground it just blows back on the detector. Best example is Equinox Beach Mode 2 automatically lowering TX so the detector can function in the worst stuff.

 

Thanks for your thoroughness Steve.

I read your post that you linked. The one titled "Selectable frequency and multi frequency". Umm ya, a rabbit hole indeed! I enjoy knowing as much as I can about how detectors work, but I don't want to get that deep into 🙂 

So without wanting to get into that any further, I just have 1 last basic question:

If transmit power is so high that it causes that "blowback", can that blowback be reduced by decreasing the receivers gain, instead of reducing transmit power?

 

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9 minutes ago, Digalicious said:

Thanks for your thoroughness Steve.

I read your post that you linked. The one titled "Selectable frequency and multi frequency". Umm ya, a rabbit hole indeed! I enjoy knowing as much as I can about how detectors work, but I don't want to get that deep into 🙂 

So without wanting to get into that any further, I just have 1 last basic question:

If transmit power is so high that it causes that "blowback", can that blowback be reduced by decreasing the receivers gain, instead of reducing transmit power?

 

As far as I understand it, no. It’s on the front end so too late for the rear end to fix the problem. Someone who knows more is welcome to lay out more than that. What would be the point though? Kind of like turning up the heat to get warmer while opening the windows to cool it down. Everything is a trade off in detecting, and there is no free lunch.

 

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Yep, there always seems to be a trade off when it comes to metal detectors.

I was hoping there was a less complex answer to my first question, but it looks like the long answer is going to make my brain bleed 😁




 

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While I don't specifically know the answers,  and I don't know what exactly they mean by more power with the Manticore, I may be able to offer a few observations:

1.) The FCC approval in the US does not seem to care about the TX power of the detector itself, they only look at TX power of the Bluetooth/wifi equipment. I've noticed this is true for the FCC reports of every detector manufacturer I've looked at. So either the TX frequencies are unregulated (thus there is no max legal TX), or they are underneath whatever the power would be which might require certification/testing.

It also appears to be a way for the companies to circumvent early release of information...just use the same old Bluetooth equipment that is already approved, or eliminate onboard BT/wifi on the unit itself. 

2.) When a manufacturer talks about "power", they need not specifically refer to TX power. They might be talking about RX amplification, or using the term colloquially. The Manticore might have the same TX power, but could just have a more sensitive RX amplification circuit.

TX power runs against a wall of diminishing returns. RX power gets pointless past a certain spot because the signals just get much smaller than the noise and so you introduce more noise than signal by boosting it.

The nice thing is - there are ways to eliminate noise and a lot of modern tech addresses more efficient signal processing. AI is good at it and getting better. Lots of chips have processing built in onboard, and new algorithms are invented/improved every year. So, the RX wall - in my opinion - is not so much a wall but a temporary barrier at this time, and we still have gains to make both in amplication and general noise reduction as detectors catch up with modern tech. 

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12 minutes ago, jasong said:

When a manufacturer talks about "power", they need not specifically refer to TX power. They might be talking about RX amplification, or using the term colloquially.

True, but in this specific case (Manticore) ML is takling specifically about transmit power as they consistently touted "50% more power to the coil" compared to Equinox.  Also, with digital signal processing it doesn't necessarily take more power to "amplify" the received signal in the sense of applying electric power to bias solid state amplification circuits, though it MAY take more processing power.  But it's really all semantics at that point...

Point is the Manticore "more power" thing was related to coil power.  And all the tradeoffs referenced by Steve in his previous post apply. 

There is also some relevant discussion in this thread: 

Since we only get the very incomplete information the marketeers feed us, it's hard to determine what any of the mumbo jumbo really means in terms of actual performance.  At this pointcwe rely solely on the documented empirical performance reports of, hopefully, unbiased, knowlegeable, and skilled end users.

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