Cellular telephone base stations are low-powered radiofrequency (RF) transmitters which operate at around 850-900 or 1800-1900 MHz (depending on the technology and region of the world). RF energy in a similar frequency range is used by many other technologies such as microwave ovens, UHF television, other communications systems, and radar. Health and safety issues related to RF energy have been studied for many years and there is an immense literature on the subject. Here are some sources that review health and safety issues related to RF energy from cellular base stations.

A fact sheet published by the World Health Organization. There is also a Spanish version available on the WHO EMF website.
Also see the IEEE EMBS Committee on Man and Radiation Report. Other reports are available through its website.
The International Commission on Nonionizing Radiation Protection (ICNIRP) has published a lot on health and safety of RF energy. See its website. The ICNIRP published an article that describes the ICNIRP exposure limits for RF energy and their scientific rationale. See "Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic, and Electromagnetic Fields (up to 300 GHz)," Health Physics Vol. 74, No 4, pp 494-522, 1998.
A very detailed assessment of the scientific evidence related to health and safety of mobile telephones and base stations is in the recent (May 2000) report by the Independent Expert Group on Mobile Phones (IEGMP) titled "Mobile Phones and Health" This study concludes "the balance of evidence to date suggests that exposures to RF radiation at levels below [international exposure guidelines] do not cause adverse health effects to the general population" but that "there may be biological effects at exposures below those guidelines." Public exposure to RF energy from cellular base stations is invariably far below the ICNIRP exposure guidelines.

Kenneth R. Foster
Professor, Bioengineering
University of Pennsylvania

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I'M SEARCHING FOR INFORMATION ABOUT THE HEALTH RISKS OF CELLULAR ANTENNAS' RADIATION. I NEED SCIENTIFIC (SCIENTIFIC PAPERS IN JOURNALS) THIS.

Cellular phones are designed to be safe for both the user and anyone standing nearby. Cellular phones are actually small radios that transmit signals to and from base-station antennas located on towers or buildings in the nearby neighborhood. Cellular phones use low-power radio signals, even weaker than CB, police, or fire radios.

The American National Standards Institute (ANSI) sets safety standards for human exposure to radiofrequency (RF) electromagnetic energy in the United States. Government agencies such as the Federal Communications Commission (FCC), the Occupational Safety and Health Administration (OSHA), and many states recognize and accept the ANSI RF safety standard. Also, the United States standard for RF energy is comparable to those set in other countries.

Cellular phones and cellular-phone base stations have been shown to meet these RF safety standards. Safety standards for RF energy are threshold standards. Threshold standards define the level of RF energy above which there may be health or safety hazards and below which there have been no reported harmful effects. Unlike ionizing radiation, which many people believe to act cumulatively even at small exposure levels, RF energy at low levels is not considered a cumulative hazard. Therefore the consensus of scientific experts in this area is that RF exposure from cellular phones, meeting the threshold levels set in safety standards, is safe for all.

The specific answer to the question is that cellular phone technology is safe for all. There is no danger posed by either handheld phone units or by base-station antennas. In both cases, the radio signals transmitted from the antennas are required to meet the ANSI safety standard for RF safety as embodied in FCC regulations governing this technology. For more information:

The FCC has recently revised and reissued its Bulletin 56 on Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields.

OSHA provides information and links to more sites on RF safety at its Web page, Radiofrequency/Microwave Radiation.

Gary Zeman, ScD, CHP Lawrence Berkeley National Laboratory

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IT MORE DANGEROUS STAY FOR ONE HOUR AT A TEN-METER DISTANCE FROM CELLULAR ANTENNA OR TALK INTO PHONE THE SAME AMOUNT OF TIME?

There are a number of opportunistic gadgets on the market to allegedly protect the user from hazards of cellular phones. You can search the Internet to find the latest, ranging from antenna shields to whole-body shielding materials. Most experts believe that these devices take advantage of customers' misunderstanding and unfounded fears to sell products with no real value. First of all, cell phones that operate within the guidelines established by national and international safety panels have never been shown to pose a health risk to the user (see answers to other questions on cell phone safety on this website). Secondly, placing any kind of shield over the antenna of a cell phone will in most cases cause it to increase its RF output as it attempts to compensate for signal loss in the shield and maintain a quality phone call. The U.S. Food and Drug Administration published an advisory on cell phones several years ago that said if you are concerned about risks of using a cell phone, then simply use it less. That is still good advice today. Gary Zeman, ScD, CHP Lawrence Berkeley National Laboratory

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ARE THERE PRODUCTS AVAILABLE TO THE GENERAL PUBLIC THAT CAN BE PURCHASED PROTECT CELLULAR OR PORTABLE TELEPHONE USERS FROM RADIATION? IF SO, WHERE THESE FOUND?

Some electronic equipment has been shown to be sensitive to radiofrequency interference from cell phones. I suggest you talk with the manufacturer of the spectrometer for information about it.

Gary H. Zeman, ScD, CHP

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IT LIKELY THAT CELLULAR PHONE USAGE COULD EFFECT A CHANGE IN 400 MHZ NMR SPECTROMETER'S MAGNET IF HAS DECENT SHIELDING (TOP-OF-THE-LINE SHIELDING, CA. 1992)?

The best single reference is the Federal Communications Commission (FCC) Website. Look for:
Bulletin 56, "Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields,"

Bulletin 65, "Evaluating Compliance With FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields,"

"A Local Government Official's Guide to Transmitting Antenna RF Emission Safety: Rules, Procedures, and Practical Guidance."
An excellent technical paper with field measurements of cell-tower emissions was published by R.C. Petersen and P.A. Testagrossa in the journal Bioelectromagnetics, volume 13, page 527ff, 1992. If you need onsite technical support and services there are various consultants available, such as Richard Tell Associates, Inc. Gary Zeman, ScD, CHP Lawrence Berkeley National Laboratory

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I NEED HELP IN GATHERING PUBLISHED INFORMATION ABOUT THE RISKS POSED BY CELL TOWERS PLACED ON SCHOOL GROUNDS. THERE WHICH WOULD ENABLE ME TO GATHER/CALCULATE OR MEASURE RADIATION SPECIFIC SITE?

If you purchase the greenLean, you will get everything you need except a router, computer to operate the machine, and software to control the machine. You state that you have a computer. You can use this computer, but you will need to determine if it has a parallel port, or if you are going to need the USB controller option. As for the software, there are too many different options for you to choose from. We would not be able to tell you which to get, and how much it will cost you. This is a matter of preference. I can tell you, however, that you will need 3 types of software to complete a CNC project. You will need CAD software to design your design, CAM software to add tool paths and convert the design to g-code, and then control software to take the g-code and operate the machine.

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I am building a wet plasma table for my shop that is 8'x 16'. I will need hardware and software. Please heko me wuth the list, My phone is 9124273734. I would like to talk with someone if possible. Thanks, Rus

It's a question of signal strength. Interference has been observed only very close to transmitting antennas where there is strong signal strength. Interference has been observed in some medical electronics due to hand-held cell phones. Roof-top antennas are some distance away from any susceptible electronics. In addition to proximity, the directionality of the antennas is important. Most rooftop antennas have strong gain in the forward direction—towards the horizon—and very low gain in the vertical direction. Finally, there are layers of building materials shielding the interior areas from the rooftop antennas. Proximity, directionality, shielding—all go towards reducing the signal strength inside a building due to the antennas on the roof so that interference is not generally an issue. This does not mean that you cannot receive the signals from the roof top antennas inside the building; it simply means that the received signals are not strong enough to cause interference. Gary H. Zeman, ScD, CHP

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HOSPITALS DO NOT ALLOW CELL PHONE USE DUE TO POTENTIAL INTERFERENCE. LAST WEEKEND I WAS IN A HOSPITAL WHERE THE TOP OF BUILDING STUDDED WITH TOWER ANTENNAS. WHY IT THAT PHONES WOULD CAUSE INTERFERENCE, BUT ANTENNAS NOT?

Generally, 3D printers require the following components:

Electronics to move the motors, limit the motion and extrude the filament:
- Stepping motors, one for each axis (X, Y and Z), and one for each extruder

- Stepping motor drivers that are capable of allowing a current draw that matches the stepping motor connected to the driver. https://www.buildyourcnc.com/item/3D-Printer-Component-electronicsAndMotors-stepper-driver-2!5a-FDMElectronics-driver2!5a

- Arduino Mega 2560 to serve as the g-code interpreter. https://www.buildyourcnc.com/item/3D-Printer-Component-electronicsAndMotors-electronic-component-arduino-mega-2560-FDMElectronics

- Arduino shield that breaks out all of the connections from the arduino (3D printer main board). https://www.buildyourcnc.com/item/3D-Printer-Component-electronicsAndMotors-3d-printer-mainboard-FDMElectronics-3dprintermainboard

- Extruder to control the temperature of the hot end (receive temperature readings using a type K thermocouple and send current to the heating cartridge, or power resistor). https://www.buildyourcnc.com/item/3D-Printer-Component-electronicsAndMotors-extruder-controller-FDMElectronics

- End stops to limit the travel of each axis. https://www.buildyourcnc.com/item/3D-Printer-Component-electronicsAndMotors-electronic-component-end-stop-switch-safety-FDMElectronics-endstop

- Type K Thermocople to sense the heat at the hot end. https://www.buildyourcnc.com/item/3D-Printer-Component-typek-thermocouple-heat-sensor-newbiehack-sensors-typek-thermocouple-heat-sensor

- Extruder with motor and hot end. https://www.buildyourcnc.com/item/3D-Printer-Component-extruder

The software to run a 3D printer for our electronics is replicatorG.

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I am building a big 3d printer using 3 nema 23 and two nema11 for dual head extruder. I need a list of the rest of the stuff I would need including hardware to run these motors and the sofware I would need.

It is not clear that mobile phones do produce brain tumors, or any serious health effects for that matter. A number of epidemiology studies have been almost completely negative on the issue.

See the article I wrote with John Moulder in IEEE Spectrum magazine and also Moulder's FAQ on mobile phones and health.

There has been a lot of discussion over the years about the possible mechanisms by which microwave energy such as emitted by cell phones might produce biological effects. The one unequivocal mechanism is the heating of tissue, but mobile phones operate at power levels that are too low to cause noticeable heating in the user. Scientists have speculated about other mechanisms, but these theories remain unproven and many of them have been challenged on biophysical grounds.

Whatever may be the risks or nonrisks of mobile phone radiation, a hands-free kit is an effective way for the user to reduce his or her exposure to radiofrequency energy while using a mobile phone.

Kenneth R. Foster, Professor
Department of Bioengineering
University of Pennsylvania

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I WOULD LIKE TO INQUIRE ABOUT THE PHYSICS PRINCIPLES REGARDING USE OF MOBILE PHONES AND DEVELOPMENT BRAIN TUMORS. I'VE BEEN THROUGH MANY SITES BUT THEY CAN NEVER GIVE AN EXACT ANSWER. REALLY SOMEONE TUMORS OR DOES IT HAVE DO WITH INTENSITY RADIATION DISTANCE BETWEEN PHONE INDIVIDUAL?

Headsets have been tested by the manufacturers and meet the current ANSI/IEEE standards for RF safety, the same standards that the Federal Communications Commission enforces under the Telecommunications Act of 1996. These standards place limits on the specific absorption rate (SAR) of radiofrequency (RF) energy in the body. Recent inflamatory articles in British press were not substantiated by testing in ISO-accredited testing facilities at Motorola. Manufacturers of cellular phones are required under FCC regulations to assure that their products meet the SAR limits on both hand-held and hands-free units. Further information may be available from the FDA or from the FCC. Ron Petersen, Lucent C.K. Chou, Motorola

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HAVE THERE BEEN ANY STUDIES OF POSSIBLE RADIATION DANGER FROM HEADSETS USED WITH HANDSETS CORDED TELEPHONES? I A TELEPHONE BATTERY-POWERED HANDSET. THIS HANDSET HAS JACK FOR HEADSET, SO YOU CAN WALK AROUND THE HOUSE AND YARD ON YOUR BELT WHILE TALK INTO HEADSET. EITHER OR HEADSET GIVING OFF RADIATION, LIKE CELLULAR PHONE? DANGEROUS AMOUNT RADIATION?

There are several endmills that would work for that application. Here's the one we use in our own shop: https://buildyourcnc.com/Item/endmill-singleflute-upcut-Onsrud-1-flute-plastic-wood-aluminum for cutting .75 inch MDO.

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Which end mill would you advise to buy for cutting in full depth MDF and plywood of up to 20mm thickness? I am about to install a 2.2k spindel on my cnc.

Dealing with our USB BoB, the potentiometer that will be used in the key jog, is a 5V, 5k - 10k Ohm potentiometer.

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I am building a cnc mill using your USB controller and i would like to know what is the specification of potentiometer used for adjusting manual axis jog speed

For the integrated computer for the blackTooth, the hard drive doe not need to be formatted, but will require an OS (operating system) to be installed. Ubuntu Linux can be installed with the CNC integrated software from Linuxcnc.org. Windows can also be installed.

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I am building the Blacktooth with integrated computer, which consists of a motherboard and hard drive. Does the hard drive need to be formatted or any form of OS loaded onto the integrated computer?

As long as the bearing has a minimum thickness of 1/4" and 9/32" is a bit thicker, there will be no problem with the book build using the bearing that is 1/32" thicker. There is actually more surface area which is better.

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I am building the CNC in your book - Build you own CNC Machine. One of the bearing thicknesses is 1/4" I can't find that bearing online. I can find 9/32, will that be a problem. Do you have a source? Thx

We have the image at that size to encourage the purchase of the kit from us. This helps to keep buildyourcnc alive and allows us to fund development of other awesome low cost machines.

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could you make available a larger size picture of the exploded view of the BlackTooth laser cutter? I would like to use for reference when building my laser cutter, but it is too small to be really useful.

There has been a lot of public concern around the world about potential health effects from using mobile phones. This concern has spilled over to other cordless phone technologies and indeed to many other devices that transmit radiofrequency energy.
Scientists have been studying possible health and biological effects of radiofrequency energy since World War II and even before, and the literature at this point is very large. Since the 1990s many studies have been conducted on possible health effects of mobile phones. I am not aware of any studies that have searched for possible health effects of DECT phones specifically, but DECT phones operate in a generally similar frequency band and at similar average power levels as many mobile phones.

Health agencies around the world have repeatedly examined the scientific literature and have found no clear evidence of health effects from use of mobile phones, or indeed from any exposures to radiofrequency energy at levels below international exposure guidelines. But these agencies also point out the limitations to the data (for example, lack of data regarding long-term use of mobile phones) and they all call for more research. The most recent report on this subject is by a group affiliated with the Health Protection Agency of the United Kingdom (U.K.) (http://www.mthr.org.uk/documents/MTHR_report_2007.pdf).

Some activist groups (such as the one whose website you cited) claim that there are health hazards from mobile phones and other sources of radiofrequency energy at levels below international exposure limits. Such claims are not reflected in opinions of health agencies including the U.K. Health Protection Agency, the World Health Organization, and other major health agencies.

That said, if a person is concerned about possible health effects of a cordless or mobile phone, he or she might consider using a hands-free kit (which reduces exposure to the head) or simply not use such a phone at all.

Kenneth R. Foster, Professor
Department of Bioengineering

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WHILE RESEARCHING A NEW CORDLESS PHONE TECHNOLOGY (DECT [DIGITAL ENHANCED TELECOMMUNICATIONS] 6.0), I SAW REFERENCE TO POTENTIAL BRAIN DAMAGE AND/OR CANCER DUE THE RADIATION FREQUENCY AND PULSES FROM THESE DEVICES.

Portable cell phones emit about 0.6 watts of radiofrequency energy, limited primarily by the power of the battery. As with any radiofrequency transmitter, there will be some amount of absorption in the human body; the amount depends on how close you are to the antenna. The Federal Communications Commission (FCC) limits the amount of radiofrequency energy which cell phones can deposit in the body to levels at which no health effects are to be expected. See an article on Cell Phone Safety on this website for more information.

Gary H. Zeman, ScD, CHP

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HOW MUCH RADIATION GIVEN OFF BY A CELL PHONE AND THERE ANY WAY TO STOP THE FROM BEING ABSORBED INTO YOURSELF?

Most motherboard do contain parallel ports, but the port connector may not be at the back (in the section where external connectors will be connected). Instead, the motherboard may contain an LPT ribbon connector on the actual face of the motherboard (usually along one of the edges). You will need a ribbon connector to a DB25 female connector.

If your motherboard does not contain an LPT header on the motherboard, you can purchase a parallel printer adapter that plugs into one of the PCI slots. The price of the adapter is very inexpensive and sometimes is actually less costly than the actual ribbon connector.

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As I am building my 20" x 24" laser engraver cutter, I notice that there is no parallel port on the onboard computer and I have the parallel breakout board any answers?

WE don't have an actual file that contains the instructions for the machines as they are a part of a larger database file that is queried during the product page's rendering in the browser. The best option would be to print the webpage on a printer and use that as notes.

I know this will not provide larger images, but you could use the paper version to write your notes while assembling the machine using the larger images on the website.

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On the blackFoot 4'x8' CNC machine do you have the instructions under one file that I can download, I want to print them out and make notes as I am building the machine.