Get FCC Approved!

[Paul]

Starting a legal metal detecting company requires a lot of money, time, and work. I merely want the garage designer to be prepared because from what I've seen here, they are playing Russian roulette if they don't get their units FCC approved!

These pulses contain wideband frequencies. Take a look at a 10KHz pulse and you'll see appreciable frequencies in the MHz range. Lets analyze radiation resistance. Enter a 2-foot coil in an antenna simulation program and you will discover that it generates a far field. It is not like a yagi antenna. Please, a yagi antenna is designed to talk around the world. I have spent about 2 decades working with NEC antenna software. I am telling you right now, you put a 400+ volt pulse on a 2-foot coil and you are asking for trouble with the FCC.

Believe me, the last thing a garage designer wants is to get caught. The U.S. government is busy, but eventually they will get around to it and then the nightmare begins. The legal system is complex, but a good place to start is with FCC Part 15 regulatory standards. It does not matter if the detector is legal, which I seriously doubt some of these new ones are. They need to get FCC approved, period.

This post is not meant as a scare tactic. Just be prepared. Get a good lawyer. In the long run it will be cheap insurance, and the smart legal thing to do. Ignorance of the law is not a defense in court!

Paul

[Boattow]

Get a life

It has become painfully obvious that you are here merely to cause grief. Go get a life. Metal detectors may output a very small, insignificant amount of incidental RF but they are not tuned RF transmitters. They are typically used where it is even less important since they aren't used in and around your house. There is no requirement for FCC approval of metal detectors and I'm pretty sure Dave is aware of this. I'm surprised you aren't.
Boattow

[Paul]

It has become painfully obvious that you are here merely to cause grief.

No. You just don't like what I have to say. Perhaps you just want to dream and ignore laws.

Metal detectors may output a very small, insignificant amount of incidental RF

Do you even know what the spectrum of a pulse looks like?

but they are not tuned RF transmitters.

You mean they're not tuned to talk around the world.

They are typically used where it is even less important since they aren't used in and around your house.

Do you really think the government cares if you give them your promise that your customers will merely use the equipment 100 miles away from the nearest home?

There is no requirement for FCC approval of metal detectors and I'm pretty sure Dave is aware of this. I'm surprised you aren't.

That's some nice wishful thinking, but not true. Even a little commonsense should tell you otherwise. Take a look at one of Fishers documents, "Advancing the Hobby of Metal Detecting"
http://www.fisherlab.com/hobby/docum...gence4thed.pdf
Quote, "When a metal detector is turned on, the power (measured in milliwatts) is a fixed/constant output, The FCC regulates maximum output/transmit power to 100 milliwatts."

Take a look at Bounty Hunters hiring page,
http://www.detecting.com/hiring/
Under "KINDS OF ADDITIONAL KNOWLEDGE & SKILLS WE REGARD AS A PLUS" see #10. It says, "Familiarity with FCC Part 15 regulations and compliance testing methods."

Have you taken a look at the EM spectrum of a good PI detector? You better learn the proper method of detecting such fields as used by the FCC. BTW, it's total radiated power.

Good luck,
Paul

[kt315]

Paul, what you will say about an magnetic emission of new super bomb.
you see - there are nothing of the laws you tell about.

http://www.telegraph.co.uk/news/grap...GSFFWAVCBQWIV0

[ElectroNovice]

Starting a legal metal detecting company requires a lot of money, time, and work. I merely want the garage designer to be prepared because from what I've seen here, they are playing Russian roulette if they don't get their units FCC approved!

These pulses contain wideband frequencies. Take a look at a 10KHz pulse and you'll see appreciable frequencies in the MHz range. Lets analyze radiation resistance. Enter a 2-foot coil in an antenna simulation program and you will discover that it generates a far field. It is not like a yagi antenna. Please, a yagi antenna is designed to talk around the world. I have spent about 2 decades working with NEC antenna software. I am telling you right now, you put a 400+ volt pulse on a 2-foot coil and you are asking for trouble with the FCC.

Believe me, the last thing a garage designer wants is to get caught. The U.S. government is busy, but eventually they will get around to it and then the nightmare begins. The legal system is complex, but a good place to start is with FCC Part 15 regulatory standards. It does not matter if the detector is legal, which I seriously doubt some of these new ones are. They need to get FCC approved, period.

This post is not meant as a scare tactic. Just be prepared. Get a good lawyer. In the long run it will be cheap insurance, and the smart legal thing to do. Ignorance of the law is not a defense in court!

Paul

It is not difficult to design a PI that complies with emissions regulations. Often the problem is not with the transmitter, but with other circuit elements i.e. voltage regulators,charge pump power supplies, high speed logic etc. If these are not properly decoupled close to the device, then there is the possibility of oscillation or ringing in the MHz region. This can then be radiated by circuit board traces, or coupled through to the coil circuit. As the TX usually takes a couple of microseconds to switch off 0.5MHz is likely to be the highest harmonic that the coil generates. Anything, from this frequency and upward, is very severely attenuated by PROPERLY designed lead or copper shielding around the coil. If the coil is PROPERLY shielded by using total wrap shielding (something that Minelab does NOT do) then nothing but the wanted signal can leak out. If you use a spectrum analyzer you can see what properly designed shielding ( not like ML do) does in preventing the propagation of undesirable emissions and preventing outside Rf getting in. Also unlike a true tuned antenna, the coil is also highly damped, so that the resonant peak, which is in the 0.5 – 1MHz region anyway, is flattened right out. With properly designed shielding, a PI coil is an extremely inefficient radiator of Rf frequencies that could potentially interfere with other apparatus. European tests for Rf emissions (i think Oz is similar? don’t know about USA) I understand start at 30MHz and go up to 1GHz, so a good design should have a very large safety margin even at the low end.

For digital devices operating at or below 1.75Mhz the bottom FCC limit for emission testing is 30Mhz! Ref “Emc for product designers” by Tim Williams.

Paul is engaging in a scare campaign. I wonder does Minelab have a compliance certificate for their Pi machines. Perhaps Paul can tell us!

ElectroNovice

[Carl-NC]

Starting a legal metal detecting company requires a lot of money, time, and work.

I wouldn't disagree with that...

Enter a 2-foot coil in an antenna simulation program and you will discover that it generates a far field.

For wavelengths roughly 4x the circumference, or about 40MHz for a 2-foot coil. The PI energy at 40MHz is mighty mighty small.

Believe me, the last thing a garage designer wants is to get caught. ... It does not matter if the detector is legal, which I seriously doubt some of these new ones are. They need to get FCC approved, period.

Approval is not a necessity for metal detectors. Compliance with FCC regs is.

Quote, "When a metal detector is turned on, the power (measured in milliwatts) is a fixed/constant output, The FCC regulates maximum output/transmit power to 100 milliwatts."

Sorry, but this is flat out wrong. It's an old myth that has circulated for years amongst metal detectorists, to explain why detectors can't be made to go deeper. I'm surprised Fisher would print that, they should know better.

The reality is that detectors need to comply with FCC regs. They probably do, with room to spare. Formal approval is not necessary, but the manufacturer should at least verify that the device complies. If it comes to the FCC's attention that a detector violates any rules, the manufacturer will simply have to cease sales until the problem is demonstrably fixed. It's not that big a deal.

- Carl

[Paul]

Approval is not a necessity for metal detectors. Compliance with FCC regs is. ... If it comes to the FCC's attention that a detector violates any rules, the manufacturer will simply have to cease sales until the problem is demonstrably fixed. It's not that big a deal.

Companies are required by law to comply with FCC rules. That's why companies get FCC approval. I'm not sure it's wise for a company to use their own instruments and just think that's good enough. I fail to see how getting caught by the FCC is no big deal.


Here's just one section from of the FCC's site:
http://www.fcc.gov/oet/info/rules/pa...t15-2-1-06.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

I am in no way simplifying the FCC's laws as they are complex / lengthy. The above is just one section. As you can see, frequencies between 0.490 MHz to 1.705 MHz must not exceed 24mV/m at 30 meters away. Frequencies between 1.705 MHz to 30.0 MHz must not exceed 2.4mV/m at 30 meters away.

[100mw] -> Sorry, but this is flat out wrong. It's an old myth that has circulated for years amongst metal detectorists, to explain why detectors can't be made to go deeper. I'm surprised Fisher would print that, they should know better.

As stated, the FCC rules are complex / length. I will quote from FCC Part 15,

Section 15.219 Operation in the band 510 - 1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.

Paul

[Carl-NC]

Companies are required by law to comply with FCC rules.

Yes, I agree.

That's why companies get FCC approval.

Some classes of devices require FCC approval. Metal detectors do not.

I'm not sure it's wise for a company to use their own instruments and just think that's good enough.

For the classes of device where this is sufficient, companies do this all the time.

I fail to see how getting caught by the FCC is no big deal.

If you build a cell phone jammer, and get caught, it's a really big deal. If you have a metal detector that somehow exceeds the radiation limits below, the FCC will NOT drag you to court, or try to close your business. They'll simply ask you to correct the problem, and show that you have done so.

Here's just one section from of the FCC's site:
http://www.fcc.gov/oet/info/rules/pa...t15-2-1-06.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

Yup, these are the limits that apply to metal detectors, at least those that operate above 9kHz. Below 9kHz, there are no rules.

I am in no way simplifying the FCC's laws as they are complex / lengthy. The above is just one section.

Actually, they're pretty simple... the table you gave just about sums it up for detectors.

As you can see, frequencies between 0.490 MHz to 1.705 MHz must not exceed 24mV/m at 30 meters away. Frequencies between 1.705 MHz to 30.0 MHz must not exceed 2.4mV/m at 30 meters away.

Sorry, but your not reading the table correctly... at 490kHz, the limit is 49uV/m @ 30m; at 1.705MHz, the limit is 14uV/m @ 30m.

- Carl

[Carl-NC]

As stated, the FCC rules are complex / length. I will quote from FCC Part 15,

Originally Posted by FCC, Part 15, Section 15.219
Section 15.219 Operation in the band 510 - 1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.

The 100mW limitation has nothing at all to do with metal detectors. Nor do (b) or (c).

- Carl

[Paul]

Carl,

You and others have concluded for who knows how many years that the 100mW is an old myth (in your own words) when I clearly showed you in FCC Part 15 that the frequency band (510 - 1705 kHz) is limited to 100mW. I think you and others should once and for all acknowledge that.

I might reply once more in this thread, but I've perhaps wasted enough of my time doing everyone's FCC research here. If I was working for MineLab, lol, don't you think I'd much rather let you guys sell your machines and sick the FCC on you?

Some classes of devices require FCC approval. Metal detectors do not.

Is that the legal advice you would give David & Eric? There is nothing mentioned in that entire FCC pdf relieving Metal Detectors from such rules! The rules apply to everything with the exception of few machines such as specific medical equipment, which is stated in the pdf.

If I am wrong then please show me in document. Perhaps there is another document that I have not seen.

For the classes of device where this is sufficient, companies do this all the time.

Sure, if the device doesn't have an antenna and to save money. I also see a lot of people doing California Rolls at stop signs just to save time. I'd hardly consider a high-performance PI metal detector with a two-foot loop antenna pulsed over 400 volts a safe bet.

If you build a cell phone jammer, and get caught, it's a really big deal. If you have a metal detector that somehow exceeds the radiation limits below, the FCC will NOT drag you to court, or try to close your business. They'll simply ask you to correct the problem, and show that you have done so.

LOL, I hope you're correct. I'm sure it's more complex than that. Cross your fingers the FCC guy's in a good mood and let's you slide. I'm sure it's more complex depending how many units you've sold, etc.

Yup, these are the limits that apply to metal detectors, at least those that operate above 9kHz. Below 9kHz, there are no rules.

As you know, an 8 KHz pulse has far far far higher frequencies than 8 KHz.

Actually, they're pretty simple... the table you gave just about sums it up for detectors.

Carl! Tell that to the judge, LOL. That entire 155 page document cannot be summed up in one tiny table. You people are responsible to comply to each and every section.



Paul

[Paul]

The 100mW limitation has nothing at all to do with metal detectors. Nor do (b) or (c).

- Carl

Show me where it says that in pdf.

[Qiaozhi]

FCC Compliance

The 100mW limitation has nothing at all to do with metal detectors. Nor do (b) or (c).

I've always suspected that was a myth, and here is a extract from some notes I made a while ago - this is for the UK, by the way:

"Whenever possible the Agency (ofcom) aims to exempt the use of the radio spectrum from licensing so as to reduce the burden on users. Many low-power devices such as metal detectors, radio controls for model aircraft and some types of radio microphones, are unlikely to cause intereference to other users. Therefore they are exempt from the requirement for a WT-Act license."

As you know, an 8 KHz pulse has far far far higher frequencies than 8 KHz.

True - but these harmonics are far far far smaller in amplitude than the fundamental. In fact, the amplitude of any given harmonic is equal to the fundamental divided by the harmonic number. Any harmonics that fall into a band covered by FCC regulations are minute in comparsion.

[Paul]

Hi,

I've always suspected that was a myth, and here is a extract from some notes I made a while ago - this is for the UK, by the way:

We were talking about U.S. laws. The 100mW quote was directly taken from the FCC Part 15 document.

True - but these harmonics are far far far smaller in amplitude than the fundamental. In fact, the amplitude of any given harmonic is equal to the fundamental divided by the harmonic number. Any harmonics that fall into a band covered by FCC regulations are minute in comparsion.

Yes, the 1 MHz voltage harmonic of 10 KHz pulse is only 1/100th, but that is not a reflection on radiated power. With radiated power we need to also consider frequency. Effective radiation resistance increase with frequency. Furthermore the effectiveness of the coil as an antenna increases with frequency. So the radiation from the coil increases with frequency. Most of the radiated power from a good PI is in its upper bands. Ferric Toes mentions sampling in 1 usec after Tx off. That makes a pretty square wave, going from high voltage to no voltage in a short period-- high dV/dt. You might be surprised at the radiated power? If you're not capturing the energy back into a cap or battery then yikes! Say you're generated 10 W of average energy into the coil, which is mostly reactive. Then you collapse it. All of that energy is going to be radiated. On the other hand, lets say you manage to capture 80% of it. Still, that's 2 W radiated. 2 Watts is far higher than 100 mW. See the FCC quote about the 100mW-- it's not a old myth.

Paul

[Unregistered]

I think that the name "paul" is much the same as Bruce Candy, or one of his stooges. Something tells me that the Minelab sales may have dropped off due to other detectors starting to give the GP platform a run for its money.

Paul sounds like the voice of a very business orientated minelab.

[Carl-NC]

Paul, I'm very familiar with the FCC regs but I can see, based on your replies in this and other threads, that you are never ever ever wrong, no matter how mistaken you might be. Therefore, I will follow the lead of Reg, Eric, and Dave, and cease wasting my time.

Your behaviour on this forum is a curious contrast to that on other forums. When you asked for assistance with your PI design here and here, your conduct was superb. In discussions about your "free energy" concept here, you implored others to "keep the discussion civilized".

Yet on this forum, anyone who disagrees with you, simply doesn't know what the hell they are talking about.

I suspect you could have some useful knowledge to share, but at this point, I doubt anyone would care to listen. You also could have tapped the expertise of various forum denizens to assist in developing your ideas on PI design but, now, surely no one would want to help. I strongly suspect that you will not find whatever it is you are looking for on these forums.

- Carl