Pulse Devil - The inside scoop

[J_Player]

Now Paul...
It is not nice to say I am putting words in your mouth unless you can prove it. You ask ...have I have heard of slander before? Slander is not possible in a public forum of printed messages. Slander refers to verbal attacks. The libel laws cover what is posted in a forum. I really don't see where I put any words in your mouth. Can you show me?

"I disagree on the discrimination part. I don't know of any VLF's much less PI detectors that can accurately tell you metal type. We see the ads on the outdoor channel during commercial breaks. They show their VLF displaying metal type, if it's a coin or this or that. Professional detectorist knows it's false advertisement.

I live near Los Angeles, CA. If you or anyone has a Pulse Devil that is making similar claims then I would very much like to try and disprove it.

I think people are getting tired of these sales scams and false ads".

So am I to conclude that when I read this segment of your post, you are EXCLUDING PI detectors from your "false ads" condemnation? You say I am putting words in your mouth? It was YOU who posted these statements. It was YOU who said "If you or anyone has a Pulse Devil that is making similar claims then I would very much like to try and disprove it". This is not a claim, it is YOUR statement. And when you consider what NC-Dave posted before you made that statement, there is no "IF" about it:

"For coin hunting a discriminating PI will provide exceptional depth while being able to reject nails and aluminum foil etc. You don't want to dig down eighteen inches to find a nail or some other piece of trash. VLF type discrimination will be an invaluable tool to the PI and allow such machines to work inland... the Pulse Devil's discrimination when set to ferrous - non ferrous is exceptionally accurate... I found a nugget right next to a rusty iron bolt".

Since you were responding to this post by NC-Dave, it is obvious you knew he was making these claims. And now you are saying you were not referring to the Pulse Devil, but only VLF machines? If you only intended to condemn VLF machines as "false advertizing" then why do it in post responding to NC-Dave making similar claims? It seems obvious to me that you are telling NC-Dave that you are intersted in trying to disprove his Pulse Devil. I am having a hard time following your logic that says you are only referring to VLF machines.

I am sure you cannot prove I am guilty of slander. Can you prove I am guilty of libel?

Item-2 concerns your "right" to speak

"Yes, that is what I believe and it is anyone's duty to try and back up their words. I did my duty by stating the science behind it. I have repeatedly requested anyone to find the errors. Rather, most of you people would rather just argue and make claims without any science or evidence.

Ok, here are your errors: You used theories to prove that the Pulse Devil can't discriminate. Just as aeronautical engineers once used theories to prove that a bee cannot fly. The fact is there is field data which proves that your theories are flawed. The field data shows that the Pulse Devil can discriminate. The field data shows the Pulse Devil located a small nugget next to an iron bolt. The field data shows the Pulse Devil does not see magnetite. Field data shows the Pulse Devil finding small coins next to large iron. There are witnesses who saw the Pulse Devil perform as stated. Just because nobody brought a Pulse Devil to you so you could run your own field tests is no excuse for using theories to prove that it can't discriminate in the face of data that says otherwise.

"J_Player, I have every right, the freedom, to state science as I understand it just as Dave, Carl or anyone else has that same freedom. You are not my dictator J_Player.

You have every right to state any variation of science that you wish, but you do not have the right to defame other people's business ventures unless you can prove that what you say is the truth. You have not done that. I have not dictated anything to you, I only asked for some proof to back up your statements, same as you have done to others. The libel laws regulate what you may or may not say, not me.

Item-3 The REAL answers from Paul:

1. Does Paul have proof that the Pulse Devil can't tell the difference between a combination of magnetite and gold. This is just a theoretical allegation? Answer: No. Paul only has theories.

2. Is Dave Emery lying to us about the Pulse Devil's discriminating abilities? Paul does not answer yes or no, only: "perhaps we'll never know".

3. Is Paul against the development of the latest generation of PI detectors? Paul does not answer yes or no. He answers with another question, followed by his discertation with words such as "slander" and "shut me up so that Dave and others can make money"... Bottom line, Paul does not answer this question yes or no. We can only speculate on his intent toward development of PI machines. From his reply, it appears to me Paul is trying to defame the Pulse Devil while paving the way to publish his own design of PI detector. But this is only my speculation in the absense of any definite answer from Paul.

4. Is Paul trying to destroy the commercial development of the Pulse Devil? Answer: No!

5. Can Paul show some examples of metal detector builders who were fined, imprisoned, or were a defendant in a court action for failure to get FCC approved or failure to comply with the FCC rules? Answer: No.

While I omitted a lot of extraneous commentary, these are the bottom line answers, and the truth of what Paul has to back up his statements.

One big concern I had was the FCC compliance. After reading the forum posts, I asked a friend who is a 35 year veteran radio engineer for several radio stations and TV stations. He told me the FCC could care less about metal detectors and electric drills. He said the only way I will have any trouble is if I have a metal detector that is causing a severe nuisance interfering with people using dedicated radio frequencies. If there are enough complaints, and the FCC feels it warrants investigation, then they will attempt to warn me to shut off my detector until I make corrections on the detector so it no longer interferes. He laughed at the thought of me going to court because I might build a Hammerhead PI. He then scanned the area around my White's PI detector, and my Excalubur with a RF sniffer and another instrument that had a spectrum analyzer attached. He moved the sensors around while I walked back an forth whith the metal detectors. When he was done, he told me I have nothing to worry about.

As far as the Pulse Devil, I see no reason to become alarmed based on the remarks made by Paul. Paul has no proof for his statements, only theories. However, it will be interesting to see if his theories work as well as the new generation of PI technology when he tests his new detector against the Pulse Devil and Goldscan-5.

Best of luck, Paul, I wait anxiously to see how your new detector will stack up against the Pulse Devil.

[Unregistered]

JC1

Hi JPlayer,

One big concern I had was the FCC compliance. After reading the forum posts, I asked a friend who is a 35 year veteran radio engineer for several radio stations and TV stations. He told me the FCC could care less about metal detectors and electric drills.



Very good, he is exactly right. Of course the FCC would never be stupid enough to Exempt anything by name such as "metal detectors" or even "electric drills" and it would be foolish to look for such, as some silly would make a metal detector out of some used mililtary surplus anti-aircraft radar set, and say see see you have to exempt me because I called it a metal detector.

They will tell you, everything must be compliant.

Anyone with a brain knows alot of it is not.

But the FCC don't want everyone to hate them, and lose funding due to bad public relations, cause they tell everyone they can't have electric drills, but they can have them in Mexico.

But not to lose heart. The European Union IS talking about everything being compliant, I say EU,,,,, for CE compliance. So could be a concern for the world marketers.

Or they will make slight exceptions, depending on strength and frequency of emissions. Even though the fundamental freq. of a PI might be under 9kHz, the harmonics are not.

Good news, not that strong to start with, and lower frequencies don't radiate that well, but alas, probably out of compliance with FCC and CE. But not really alot to interfere will at these lower frequencies but still rules is rules,,,,,,,,,,,,,


rules with exceptions are not rules ----- Some Smart Guy

JC

[Ferric Toes]

Hi JC and All,

CE (EU) regulations are similar in many respects to the FCC. Emissions are measured from 30MHz up to 1GHz. Below 30MHz, if is is a piece of mains (line) powered equipment, conducted measurements are taken from 450kHz to 30MHz. A battery operated detector, cannot conduct interference back on to the line, so only the radiated emissions apply. Since they start at 30MHz, even a powerful, PI is not going to be emitting any significant energy that high, and above. That is, of course, provided everything is properly designed, even down to the circuit board layout. A emc consultant I had dealings with, said that, if the board is properly designed, then an outer screened box should not be necessary. As far as radiation from the coil goes, a good grounded shield will give a high attenuation of any harmonics in the MHz region.

According to a book I have, "EMC for Product Designers" by Tim Williams, under "FCC rules", it says a manufacturer can verify his own product and that "verification requires that the manufacturer satisfies himself that the equipment meets the technical requirements"

In the EU, in this respect, there is a term "due diligence". If you self certify, which is the equivalent of verification, then you have to be prepared to demonstrate that you have done all you reasonably can, to make the product comply. Officialdom is more interested in those who blatantly and wilfully disregard the rules, and refuse to implement any emc measures.

Eric.

[Muntari]

Hi Ferric Toes,

Having just gone through the CE and FCC approvals proccess here in Australia for an export product I can agree with what you say.

Basically good design for EMC from the start will ensure very minimal pain (usually) other than approval $$ for testing.


Brian K

[pml]

J_Player,

It was YOU who said "If you or anyone has a Pulse Devil that is making similar claims then I would very much like to try and disprove it". This is not a claim, it is YOUR statement. And when you consider what NC-Dave posted before you made that statement, there is no "IF" about it

You say, "there is no "IF" about it." The "if" in my statement has nothing to do "if" I did anything. The "if" in my statement is requesting people who have a pulse devil who are making similar claims as the VLF commercials to let me know.

Can't you see where the statement gives the condition by the "if?" Can't you see where I use the word "similar claims" which is ***directly*** below my statement "We see the ads on the outdoor channel during commercial breaks. They show their VLF displaying metal type, if it's a coin or this or that. Professional detectorist knows it's false advertisement."

"For coin hunting a discriminating PI will provide exceptional depth while being able to reject nails and aluminum foil etc. You don't want to dig down eighteen inches to find a nail or some other piece of trash. VLF type discrimination will be an invaluable tool to the PI and allow such machines to work inland... the Pulse Devil's discrimination when set to ferrous - non ferrous is exceptionally accurate... I found a nugget right next to a rusty iron bolt".

Since you were responding to this post by NC-Dave, it is obvious you knew he was making these claims. And now you are saying you were not referring to the Pulse Devil, but only VLF machines?

My statement is very clear. Let's break it down and analyze it for you:

If you or anyone has a Pulse Devil that is making similar claims then I would very much like to try and disprove it

If you or anyone has a Pulse Devil ...

This is clearly a conditional.

If you or anyone has a Pulse Devil that is making similar claims then I would very much like to try and disprove it"

Similar claims to VLF commercials. If you look at the previous statement you will clearly see that I was talking about VLF commercials.

If you or anyone has a Pulse Devil that is making similar claims then I would very much like to try and disprove it

This is in reference to my "if" condition. So "if" someone has a Pulse Devil, and "if" they are making similar claims, "then" I would very much like to "try" and disprove it.

This is not a claim, it is YOUR statement.

I am not going to keep asking you. The "if" in my quote makes the sentence an "if" not a claim.

It is not nice to say I am putting words in your mouth unless you can prove it. You ask ...have I have heard of slander before? Slander is not possible in a public forum of printed messages. Slander refers to verbal attacks.

Oh you have no idea. It is very possible. Any written form of communication can be slanderous. I am documenting your words for the possibility of slander.

I really don't see where I put any words in your mouth. Can you show me?

Here is one:

Paul is painting a picture that the public is being decieved by false claims made by PI designers.

I even requested from Dave what his definition of "accurate" was. I also asked Dave if he is claiming that his Pulse Devil cannot be tricked.

If you only intended to condemn VLF machines as "false advertizing" then why do it in post responding to NC-Dave making similar claims?

Oh no! I am very much questioning any claims that Dave's PI cannot be tricked.

It seems obvious to me that you are telling NC-Dave that you are intersted in trying to disprove his Pulse Devil.

Yes, I am! And it is my right to question the claims of anyone and you can never in a million years scare me away. Are you kidding me?! I love blunt and "in your face" statements.

I am having a hard time following your logic that says you are only referring to VLF machines.

Then you should have asked me before trying to put words in my mouth. It seems your damage is already done. I even broke the statement down for you. Can't you see where the statement gives the condition by the "if?" Can't you see where I use the word "similar claims" which is ***directly*** below my statement "We see the ads on the outdoor channel during commercial breaks. They show their VLF displaying metal type, if it's a coin or this or that. Professional detectorist knows it's false advertisement."

Ok, here are your errors: You used theories to prove that the Pulse Devil can't discriminate.

You are not listening. Your statements are so vague. You know that I clearly stated that it is possible to accurately discriminate. I even said that IMO it requires high frequency. Also I must conclude that since you read my posts you are aware that I requested from Dave his definition of "accurate" and that I requested if Dave believes his Pulse Devil can be tricked. I have no idea if all these concepts are difficult for you juggle in your mind at once, but IMO it should be simple.

Just as aeronautical engineers once used theories to prove that a bee cannot fly.

I think it is very clear that you are trying to paint a diliberate false picture of me. You know darn well that I stated it is possible. Furthermore, I even said that my hats off to Dave or Eric if they can build such a metal detector.

The fact is there is field data which proves that your theories are flawed. The field data shows that the Pulse Devil can discriminate. The field data shows the Pulse Devil located a small nugget next to an iron bolt.

That is fuzzy logic! I already posted a method of how a nugget can be detected next to a piece of iron. It is fuzzy logic because if I can find a piece of gold next to iron does NOT mean that I can trick the machine or that the machine is flawless. Heck, Minelab GP has iron discrimination. You think ML added some feature that never works. Of course not. According to your mentality, if ML can detect a piece of gold near iron then it must be flawless.

The field data shows the Pulse Devil does not see magnetite.

Big deal! Just increases the delay between pulse and sample and you can do that. That's what's so great about PI's.

Field data shows the Pulse Devil finding small coins next to large iron.

Post the field data. I posted two field data requests.

Just because nobody brought a Pulse Devil to you so you could run your own field tests is no excuse for using theories to prove that it can't discriminate in the face of data that says otherwise.

I think you have a huge mental filter and you see only what you want to see. I clearly stated it is possible to build a PI discriminator. I have every right to post my theories and question if Dave's does it. Lets see all this field data? How detailed is it? How many targets were dug? I want to see data to back up claims. How does it handle a fist size nugget or lead that is flattened out on different types of magnetic material?

You have every right to state any variation of science that you wish, but you do not have the right to defame other people's business ventures unless you can prove that what you say is the truth.

You sound like you have some business connections with Dave. I clearly posted questions for Dave. How odd that Dave did not answer them. Why? What does he have to lose.

3. Is Paul against the development of the latest generation of PI detectors? Paul does not answer yes or no. He answers with another question, followed by his discertation with words such as "slander" and "shut me up so that Dave and others can make money"... Bottom line, Paul does not answer this question yes or no. We can only speculate on his intent toward development of PI machines. From his reply, it appears to me Paul is trying to defame the Pulse Devil while paving the way to publish his own design of PI detector. But this is only my speculation in the absense of any definite answer from Paul.

I said, "Now how could I be ..." If that's not clear enough for you then how is this answer, "NO!" So much for your theories about me, lol.

I asked a friend who is a 35 year veteran radio engineer for several radio stations and TV stations. He told me the FCC could care less about metal detectors and electric drills.

First of all that is hearsay. Second, did you make it clear to your friend this is in regards to a business selling detectors and nothing to do with personal use?

He said the only way I will have any trouble is if I have a metal detector that is causing a severe nuisance interfering with people using dedicated radio frequencies. If there are enough complaints, and the FCC feels it warrants investigation, then they will attempt to warn me to shut off my detector until I make corrections on the detector so it no longer interferes.

Ah, that's what I thought. It is common sense that it could be a little more severe for a business.

As far as the Pulse Devil, I see no reason to become alarmed based on the remarks made by Paul. Paul has no proof for his statements, only theories.

You left out "questions." I posted several questions for Dave and find it interesting that he has yet to answer them. Anyhow, who said anything about being alarmed? I guess you are against the exchange of information.

However, it will be interesting to see if his theories work as well as the new generation of PI technology when he tests his new detector against the Pulse Devil and Goldscan-5.

LOL, here we go again with your filtered mentality. I will remind you yet once again that I stated it is possible and my hats off to Dave or anyone who does it. I stated my theories and stated several examples how a PI can be tricked. YET I clearly stated many times that it is possible with 100+ MHz frequencies. If Dave or Eric or anyone can do it under 100 MHz then my hats off to them. Did you get that J_Player?

Best of luck, Paul, I wait anxiously to see how your new detector will stack up against the Pulse Devil.

LOL, aren't you going to add your usual thing about me selling it??? Please lower your filters for the yet one more time statement -> I intend on giving away my designs after I test it on the field to see how much deep gold there is. Will I give it away some day? Of course I cannot guarantee it. If I find endless amounts of deep gold, lol, then it could be years before I give it away, but I will not hold my breath on that one. It could take months before I fine tune it. If by chance some metal detecting company offers to buy it from me after I thoroughly prove it works then will I sell it? I have no idea. If their offer is enough to catch my attention then yes. For now, I am really not interested in little cash so presently I have no intensions of seeking money. Is that clear enough J_Player?

Best wishes,
Paul

[pml]

Hello Eric,

CE (EU) regulations are similar in many respects to the FCC. Emissions are measured from 30MHz up to 1GHz. Below 30MHz, if is is a piece of mains (line) powered equipment, conducted measurements are taken from 450kHz to 30MHz.

I posted this before by FCC Part 15:

Here's just one section from of the FCC's site:
http://www.fcc.gov/oet/info/rules/p...rt15-2-1-06.pdf

Frequency Field Strength Measurement Distance
(MHz) --- (microvolts/meter) --- (meters)
---------------------------------------------
0.009 - 0.490 --- 2400/F(kHz) --- 300
0.490 - 1.705 --- 24000/F(kHz) --- 30
1.705 - 30.0 --- 30 --- 30
30 - 88 --- 100 ** --- 3
88 - 216 --- 150 ** --- 3
216 - 960 --- 200 ** --- 3
Above 960 --- 500 --- 3

Are you saying the above general FCC table does not apply?


Thanks for all great posts on FCC rules. I still like to see things in writing rather than hearsay, but for now I have to still conclude that JC1 said it best. I gather that JC1 is saying that the FCC will not except anything, but the odds are slim and none that they will not bother a company. Also I have to conclude that it is wise for a business that creates and sells metal detectors to at least do some basic emission checks on the machines just make sure you're not killing radios and TV to prevent people from reporting FCC complaints.

Thanks,
Paul

[Unregistered]

JC1

Hi Eric and all,

What about the new FCC Part 15 Self Declaration Procedures?

Under the new procedures for DoC/Self Declaration there is no longer a need to submit/certify computing devices and peripherals with the FCC.

EMC Directive

What is the EMC directive?

The EMC directive is just one of many pieces of European legislation designed to produce uniform technical regulations throughout Europe and to foster trade between European countries. Because the standards have been selected mostly from existing international standards it is hoped to have a neutral effect with the rest of the World.

Simply put, the EMC directive requires products to generate no harmful electromagnetic emissions and be immune to defined electromagnetic disturbances and phenomena.

What are the penalties for non-compliance?

The EMC directive requires the EU member states to take all appropriate measures to ensure compliance.

These agencies will test equipment thought not to comply and if they are proven non-compliant, prohibit sales in Europe. They can even seize products or entire systems.

The person found guilty of knowingly affixing a CE marking to non-compliant equipment is liable to criminal prosecution. The penalty is a fine and up to 6 months imprisonment.

Can I complete testing required to show compliance to the LVD myself, or must I use a third party lab?

A CE marking according to the Low Voltage Directive is a manufacturer's self declaration of conformity. The manufacturer is obligated by law to be able to support their claim with proof that the product meets the essential health and safety requirements of the directive. This test data can be obtained from a third party, or manufacturers can provide it themselves.

The benefits of using an outside lab include tapping into their expertise, the tractability of the data, and impartial approach.

http://www.pseinc.com/faq.htm

Have a nice day!

JC




New Requirements in International EMC Standards

Daniel D. Hoolihan
Many new changes to international EMC standards means keeping a watchful eye to ensure compliance.

A flurry of changes to some international electromagnetic compatibility (EMC) standards have been officially published in the last several months. These EMC standards include both emission and immunity requirements. Typically, these international EMC standards are adopted by various countries and economic regions worldwide, and they become part of the regulatory environment that electronic products must cope with in their product life.

CISPR 16-2, Consolidated, Edition 1.2. Specification for Radio Disturbance and Immunity Measuring Apparatus and Methods—Part 2: Methods of Measurement of Disturbances and Immunity. For this edition, a new Annex E was added to the base document. It is an informative annex, titled "Measurement of Disturbances in the Presence of Ambient Emissions." The new edition also added significant information in clause 2.6.5 (measurements of in situ equipment), including:

*
Applicability of and preparation for in situ measurements (2.6.5.1).
*
Field-strength measurements in the frequency range 9 kHz to 30 MHz (2.6.5.2).
*
Field-strength measurements in the frequency range above 30 MHz (2.6.5.3).
*
In situ measurement of the effective radiated disturbance power using the substitution method (2.6.5.4)
*
Documentation of the measurement results (2.6.5.5).



http://www.ce-mag.com/archive/03/ARG/hoolihan.html

[Unregistered]

Hello Eric,


I posted this before by FCC Part 15:


Are you saying the above general FCC table does not apply?


Thanks for all great posts on FCC rules. I still like to see things in writing rather than hearsay, but for now I have to still conclude that JC1 said it best. I gather that JC1 is saying that the FCC will not except anything, but the odds are slim and none that they will not bother a company. Also I have to conclude that it is wise for a business that creates and sells metal detectors to at least do some basic emission checks on the machines just make sure you're not killing radios and TV to prevent people from reporting FCC complaints.

Thanks,
Paul

I'm glad to see you've changed your postion on this with your weak arguements...

[NC-Dave]

Detectors and the FCC

I worked for years designing data radios. Part of my job was to get them through FCC testing. I once spoke with John Reed who is or at least was the FCC's head of rule making about metal detectors.

John quoted the radiated emission limits which are very similar to those posted by Eric for Europe. He also added that there was not a single Ground Penetrating Radar (GPR) unit which would legally pass the FCC's limits. This was followed by his admitting that the limits were not enforced as the device in question is classified by the FCC as an unintentional radiator. All metal detectors radiate some energy. the term "unintentional radiator" simply means that the device is not designed for any form of communication with a distant receiver.

The Pulse Devil easily passes both the European and the FCC's requirements for an unintentional radiator. The pulse frequency of the Pulse Devil is only 245 pulses per second. The transmit coil current rises exponentially for the entire pulse period of 250uS.

As to fooling the discrimination, lets just say that the Pulse Devil's discrimination is on par with the best Minelab VLF's. Nothing is totally foolproof but I believe that most people would prefer to rely on their detectors discrimination abilities and maybe lose a very small percentage of targets rather than digging hundreds of pieces of iron. Hour for hour, the people using discrimination will find more as they dig far less targets. Many sites in Europe are so infested with iron that an all metal detector is useless. You will receive signals every few inches. It would be easier to simply leave ones detector at home and dig and sift every square inch by hand.

Let's wait until the reports come in from the field before judging the Pulse Devil. We will see what we will see!!!

I think it's time to stop the argument that has been blazing away on this forum. We will all benefit from keeping the threads constructive.
PEACE IN OUR TIME!!! Dave. * * *

[Charles (Upstate NY)]

Let's wait until the reports come in from the field before judging the Pulse Devil. We will see what we will see!!!

Ahem, its only 3pm shouldn't you be busy working in the shop building Pulse Devils Mr. instead of browsing the forums?

[pml]

Thanks for the reply Dave.

As to fooling the discrimination, lets just say that the Pulse Devil's discrimination is on par with the best Minelab VLF's. Nothing is totally foolproof but I believe that most people would prefer to rely on their detectors discrimination abilities and maybe lose a very small percentage of targets rather than digging hundreds of pieces of iron.

That answer my main question.

Hour for hour, the people using discrimination will find more as they dig far less targets. Many sites in Europe are so infested with iron that an all metal detector is useless. You will receive signals every few inches. It would be easier to simply leave ones detector at home and dig and sift every square inch by hand.

That is fine. Yet I am wondering if you are referring to the issues of magnetic materials that plague VLF's. That would indeed be some terrible ground if it's electrically conductive iron every few inches.

Thanks,
Paul

[pml]

I'm glad to see you've changed your postion on this with your weak arguements...

I should let such comments slide, but in all fairness is seems people are acknowledging my FCC Part 15 emission table quote and the FCC does not exempt any such items from its rules. In all fairness, what I have added / changed and very glad to acknowledged is the FCC seems uninterested in spending time enforcing such laws on metal detecting companies.

Peace,
Paul

[NC-Dave]

Iron in England

The iron I am referring to is man made. Much of it has been in the ground since the early iron age. This means that it could have been in the ground for 2500 years as the iron age in Britain started circa 500BC. Some of this iron has disintegrated into rust spots. Other pieces are still very much intact. A friend of mine found an intact Roman spear head from about 300AD in a field near where my old mother lives. For those who don't know, I am from England but I now live in North Carolina USA.

[Ferric Toes]

Are you saying the above general FCC table does not apply?

No, it is there in the FCC regulations, so it must apply to something. In all of the part 15 regulations, there is no mention of metal detectors, and whether they are classed as intentional or unintentional radiators. If they are intentional radiators, then the table has some relevance.
Most PI metal detectors operate well below a pulse rate of 9kHz. Dave’s operates at 245 pulses per sec., and I use between 1 and 3 kHz, depending on the application. If measurements start at 9kHz, then we are looking at a harmonic of the fundamental repetition rate. So for a TX pulsing at 3kHz, this would be the third harmonic. Looking at the table, the measuring distance so as to be in the far field is 300 metres, at which the field strength must not exceed 2400/9, or 266uV/m.. For repetitive waveforms, measurements are done either as a quasi peak, or average reading, so the lower the rep. rate, the safer you are. From my experience, a field strength of 266uV/m at 300m, from an 11in coil is a virtual impossibility, particularly as we are looking at least from the 3rd harmonic.

One of Humanities problems is inability to handle bluntness and "in your face" comments.

Whatever happened to tact, and consideration of another person’s viewpoint? These are two things that contribute to peace on the forums, and life in general. Bluntness and in your face comments just get peoples backs up and cause conflict, as we have seen.

Eric.

[Carl-NC]

In all of the part 15 regulations, there is no mention of metal detectors, and whether they are classed as intentional or unintentional radiators.

From 15.3:

(o) Intentional radiator. A device that intentionally generates and
emits radio frequency energy by radiation or induction.

Since metal detectors generate RF energy by induction, and since they are not specifically mentioned anywhere in the regs, then the general requirements in 15.209 are all that apply.

Metal detectors are horribly inefficient radiators of RF energy (all near-field induction, no far-field radiation to speak of), so it is unlikely that the limits in 15.209 will ever be violated.

- Carl