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Question #: 260

Question: THERE ANY STANDARD FOR A DISTANCE BETWEEN CELLULAR BASE STATION AND RESIDENTIAL AREA?

Current Solution

The two main constraints on siting cellular base stations near residential areas are government exposure limits and local zoning ordinances. Various governments have limits for human exposure to radiofrequency (RF) energy that must be complied with in the siting of cellular base stations and other transmitters. In the United States, the relevant limits are those of the Federal Communications Commission (FCC). Cellular base stations use low-powered transmitters, and RF signal levels are invariably below FCC limits at any distance more than a few feet from the antennas. Thus it is entirely feasible to locate cellular base stations on rooftops of apartment buildings and to locate communications towers within residential areas and indeed these are both common practices. Local zoning ordinances are a different story. Local governments commonly restrict the location of communications towers through zoning ordinances, and they may have provisions that restrict cellular base stations in residential districts. Local attorneys or government officials should be consulted for advice about local requirements, which vary greatly among jurisdictions. Kenneth R. Foster Professor, Department of Bioengineering University of Pennsylvania

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Other Possible Solutions to this Question

  • Is there any precision or accuracy difference between the vertical and blacktooth lasers?

    I will address the two separately (precision and accuracy):

    Precision (repeatability):
    This is most closely related to the resolution. The blackTooth uses the same mechanical drive (timing belts and pulley) of the same ratios and specifications, so the two machines will be the same in this respect.

    Accuracy:

    The output of the machine (the final physical work) matching the input given to the machine (the design data or instructions for the machine to product the physical work. This has to do with both resolution and how well the machine will hold up over time and through environmental changes.

    With that said, both machines have very similar attributes in mechanics and structure. The overall structure is made of MDO (Medium Density Overlay) and has a very low coefficient of linear expansion with regards to temperature change, so accuracy will not be affected in any appreciable manner over time with the two machines. The Vertical Laser XL does use more industry standard rails to hold the heavy gantry, but this will be differ appreciably since the blackTooth will exhibit rigidity by virtue of its size.

    It really is best to consider the application and size as the main aspects of deciding between these two machines.

    Hope this helps.


    Additional Information:
    We're looking at getting the vertical so we can run both large and small jobs on the same machine. It sounds like running a small job on the vertical (using a positioning jig) would provide results at least as
    good as running the same job on the blacktooth. Does this sound about right?

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    Is there any precision or accuracy difference between the vertical and blacktooth lasers?

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

    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?

  • Distance from laser tube exit to working point is 100 inches and three mirrors in between, is that a problem?

    The maximum length from the exit of the laser to the focus point (what we recommend) is 60 inches. You will see a slight decrease in intensity from the laser with increased length, also adding more mirrors in-between the laser tube and the focus lens in the laser nozzle will also decrease the power/intensity.

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    Distance from laser tube exit to working point is 100 inches and three mirrors in between, is that a problem?

  • Is there a wiring diagram for hooking up your hex inverter between your USB breakout board and the controller?

    The use of the hex inverter in the application to invert a direction signal to have a motor run in the reverse directions is relatively simple.

    First, go to this link and look at the chip diagram:
    https://www.buildyourcnc.com/item/electronicsAndMotors-hex-inverter-breakout-newbiehack-integrated_circuits-hex-inverter

    Connect 5V from the USB interface tothe VCC pin. The pin on the keyboard jog header can be used. Connect the GND pin from the USB interface to the GND pin on the hex inverter. Connect the CW terminal from the USB interface to the 1A pin on the hex inverter. Connect the 1Y pin from the hex inverter to the driver.

    Additional Information:
    I got a question??? I am a dummy when it comes to cnc. I got 6040 1500kw water cold engraver 3 axis from china. I can not get anything out of them pertaining help they keep telling me the same thing over and over and over and I'm doing it and send them pictures that I know. Anyway email me a wiring diagram for the PRT 1500 watt spindle motor control box and has the emergency stop on and off switch manual PC and of course yhe screanm fultonsbusiness@gmail.com

    Additional Information:
    I got a question??? I am a dummy when it comes to cnc. I got 6040 1500kw water cold engraver 3 axis from china. I can not get anything out of them pertaining help they keep telling me the same thing over and over and over and I'm doing it and send them pictures that I know. Anyway email me a wiring diagram for the PRT 1500 watt spindle motor control box and has the emergency stop on and off switch manual PC and of course yhe screanm fultonsbusiness@gmail.com

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    Is there a wiring diagram for hooking up your hex inverter between your USB breakout board and the controller?

  • I AM TAKING THE FINAL YEAR PROJECT IN BASE STATIONS AND AIR INTERFACE. WOULD LIKE TO HAVE SOME INFORMATION.

    The Federal Communications Commission (FCC) is the primary federal agency responsible for safety aspects of modern-day wireless telecommunications systems. The FCC's Internet address is shown below. Recently FCC published an excellent report, cited below, to assist citizens and local governments dealing with siting of telecommuncations towers. This report contains charts and figures describing the characteristics and performance of telecommunications antennas. The report also contains practical guidance on application of provisions of the Telecommunications Act of 1996, which is the governing legislation regarding safety and siting of wireless telelcommunications facilities. Web page: RF Safety Program Page. Report title: "A Local Government Official's Guide to Transmitting Antenna RF Emission Safety: Rules, Procedures, and Practical Guidance." The Local and State Government Advisory Committee (LSGAC) and the FCC have developed this guide to aid local governmental officials and citizens in understanding safety issues related to radiofrequency emissions from telecommunications towers. Gary Zeman, Sc.D., CHP Lawrence Berkeley National Laboratory

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    I AM TAKING THE FINAL YEAR PROJECT IN BASE STATIONS AND AIR INTERFACE. WOULD LIKE TO HAVE SOME INFORMATION.

  • WHAT ARE CURRENT RECOMMENDED IEEE EMF OCCUPATIONAL EXPOSURE LEVELS AND GUIDELINES FOR RADIO BASE STATION ANTENNAS?

    The following answer assumes "radio Base Station Antennas" refers to base stations used for personal wireless communications services such as cellular telephone, Personnel Communications Services (PCS), and Enhanced Specialized Mobile radio (ESMR). In the United States, the frequency band allocated for base stations used for personal wireless communications is 869-894 MHz for cellular service, 851-866 MHz for ESMR, and 1930-1990 MHz for PCS. The IEEE exposure limits (maximum permissible exposure—MPE) for occupational exposure (controlled environments where exposures may be incurred by persons who are aware of the potential for exposure) are frequency dependent and are expressed in terms of incident power density. The appropriate value to compare with the MPE is the incident power density averaged over the vertical cross-section of the human body. The occupational exposure limits are also time-averaged over any six-minute interval. The IEEE C95.1-1991 MPE values are shown in the table below:
    IEEE C95.1-1991 Maximum Permissible Exposure (MPE) Values
    Frequency Band Power Density
    General mw/cm2 W/cm2
    851-866 MHz f/300 mW/cm2 2.84-2.88 28.4-28.8
    869-894 MHz f/300 mW/cm2 2.90-2.98 29.0-29.8
    1930-1990 MHz f/300 mW/cm2 6.43-6.63 64.3-66.3
    NOTE: f is in MHz
    As indicated above, these values are for continuous exposure (t > 6 minutes) and are to be compared with the spatial average of the incident power density. all base stations used for personal wireless telecommunications services in the United States are required to comply with the FCC limits (as mandated by the Telecommunications Act of 1996). The FCC limits are based on a hybrid of the IEEE limits and the 1986 recommendations of the National Council on Radiation Protection and Measurements. The FCC MPEs are the same as the IEEE values for frequencies below 1500 MHz but are capped at 5 mW/cm2 (50 W/cm2) for frequencies greater than 1500 MHz.

    Both the FCC and IEEE MPEs for exposure of the public (uncontrolled environments) are one-fifth of the above values. As above, the value to compare with the MPE is the incident power density averaged over the vertical cross-section of the human body. The averaging time for the general public is 30 minutes. Thus, for transient exposures lasting six minutes or less, the MPEs for occupational exposure and exposure of the general public MPEs are the same. For cases of simultaneous exposure from antennas operating in different frequency bands, the ratio of the spatially averaged incident power density in each frequency band to the corresponding MPE for that band is determined and the sum of all such ratios must be less than unity in order to comply.

    R. C. Petersen
    Manager, Wireless and Optical
    Technologies Safety Department

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    WHAT ARE CURRENT RECOMMENDED IEEE EMF OCCUPATIONAL EXPOSURE LEVELS AND GUIDELINES FOR RADIO BASE STATION ANTENNAS?

  • With UPS standard shipping to Canada, will there be extra fees upon delivery? (on a potential +$2000 order)

    For shipment arriving via UPS STANDARD® or VIA OTHER COURIERS/TRANSPORTATION COMPANIES - For this example = $1,600.01 to $2,500.00 Value for Duty would be
    = $103.90 Each additional $1,000 thereafter would be + $7.50. For shipments arriving via UPS WORLDWIDE EXPRESS PLUS, UPS WORLDWIDE EXPRESS FREIGHT, UPS WORLDWIDE EXPRESS SAVER, AND UPS WORLDWIDE EXPEDITED SERVICES it is FREE!

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    With UPS standard shipping to Canada, will there be extra fees upon delivery? (on a potential +$2000 order)

  • Is there a significant difference between timing belt and chain drive systems?

    Repeatability is very good for these machines and can be as low as .001" depending on the way you control the machine. If you use the spindle, you can be moderately aggressive, but you will want to use a finishing pass to make sure the edges are exactly what you would expect. since this is a kit, there will be varying levels of repeatibility depending on how well the kit is assembled and maintained. Calibration, as with all machines, is a critical aspect of keeping repeatibility over time.

    Timing belts and chain are about the same when it comes to precision as long as the chain wraps most of the drive sprocket. There are differences to each of these systems as Kevlar with steel cables impregnated within the Kevlar and the steel used in roller chain have different coefficients of linear expansion (the expansion and contraction over temperature change), and roller chain may stretch over time, so it is important to maintain the machine by tensioning the chain and timing belt, and calibrating the machine over time and when the temperature changes significantly.

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    Is there a significant difference between timing belt and chain drive systems?

  • how much is the planet-cnc key for the diy cnc? What does planet-cnc replace in standard cnc?

    The base price for planet cnc is 69 Euros, which translates to $85.85 dollars. Can be found here (http://www.planet-cnc.com/index.php?page=shop)

    Additional Information:


    Additional Information:

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    how much is the planet-cnc key for the diy cnc? What does planet-cnc replace in standard cnc?

  • What length of wire do you recommend for the black toe (2'x4') between the spindle and VFD?

    The length of the cable from the VFD (Variable Frequency Drive) to the actual spindle should be about the same as the z-axis cable from the z-axis motor to the z-axis driver which is recommended at 11 feet. This is locating the VFD about at the midpoint of the machine.

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    What length of wire do you recommend for the black toe (2'x4') between the spindle and VFD?

  • Is there any sort of warranty provided by the manufacturers for the 40w laser tube?

    We included our 30 day warranty, but since it is considered a consumable and is considered to run the expected length (1000 HRS) the manufacture does not included a warranty.

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    Is there any sort of warranty provided by the manufacturers for the 40w laser tube?

  • Are there any instructions for use the USP breakout board for a CO2 laser?

    The instructions to connect the USB CNC Interface for the blackTooth Laser Cutter and engraver can be found on instruction #18 on thispage: https://www.buildyourcnc.com/blackToothLaserCutterAndEngraver.aspx

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    Are there any instructions for use the USP breakout board for a CO2 laser?

  • Are there any other manuals for the VFD that comes with the 2.2kw spindle?

    We have manuals for the VFD rather than the spindles. Can you specify what issue you may be having so we can help you better?

    Additional Information:
    I am having trouble wiring the VFD. (From the wall outlet to the VFD) I think the manual or setup guide on your website is wrong. The two diagrams show two different sets of terminals on the page.

    Also, do you have a video or other documentation on programming the VFD? Your videos and documentation looks like it only covers the 1.2kw version. Are the two different spindles from different manufacturers?

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    Are there any other manuals for the VFD that comes with the 2.2kw spindle?

  • Are there any videos detailing wiring of limit switches and stop button?

    This video may serve helpful on the homing and limit switches:
    https://www.buildyourcnc.com/PrimeronHomingandLimitSwitches.aspx

    I don't go into great detail on the wiring, however. If after you watch that video and you still need a video, please let me know and I will make a video on the wiring of limit switches and the E-stop button.

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    Are there any videos detailing wiring of limit switches and stop button?

  • Is there any way i can order replacement wooden parts for a cnc machine

    Yes, you can order replacement wooden parts, but since we don't have them as products on the website, you will need to call us directly using the number at the top right corner of the website by hovering over "need help?"

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    Is there any way i can order replacement wooden parts for a cnc machine

  • Are there contour type brushes available for leadscrews and round rails

    Yes, you can use these flexible strip brushes and create a mount for the contour that you need:

    https://www.buildyourcnc.com/item/strip-brush

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    Are there contour type brushes available for leadscrews and round rails

  • I can't spot the differences between 4'x8' blackFoot and the 4'x8' greenBull (except for laser head option): please, can you tell me?

    Only our greenBull CNC machines will be able to use the long Z-axis, due to structural construction of the greenBull over the blackFoot.
    The height from the table top to the bottom of the gantry is: 4.25"

    Both the maximum cutting height and diameter, will be dependent on the specific end mill/router bit you plan on using, since they can vary in length.
    The maximum cutting height (useful to engrave or cut material)is: with spoil-board 3.875", without a spoil-board is 4.625"
    The maximum diameter will (estimated) is: 3"

    Specifically dealing with our greenBull long Z-axis CNC machines, depending on how you specifically design the table you can have more cutting height and a larger diameter clearance. If you only create a frame for the machine with a hollow center(adjustable midsection), allowing you to have a greater clearance.
    Similar table image here: (https://buildyourcnc.com/Item/cnc-machine-greenBull-v4-6X#prettyPhoto/5/)

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    I can't spot the differences between 4'x8' blackFoot and the 4'x8' greenBull (except for laser head option): please, can you tell me?

  • What resolution and level of repeatability can one usually expect from a kit-built cnc, and is there a significant difference between timing belt and chain drive systems?

    Repeatability is very good for these machines and can be as low as .001" depending on the way you control the machine. If you use the spindle, you can be moderately aggressive, but you will want to use a finishing pass to make sure the edges are exactly what you would expect. since this is a kit, there will be varying levels of repeatibility depending on how well the kit is assembled and maintained. Calibration, as with all machines, is a critical aspect of keeping repeatibility over time.

    Timing belts and chain are about the same when it comes to precision as long as the chain wraps most of the drive sprocket. There are differences to each of these systems as Kevlar with steel cables impregnated within the Kevlar and the steel used in roller chain have different coefficients of linear expansion (the expansion and contraction over temperature change), and roller chain may stretch over time, so it is important to maintain the machine by tensioning the chain and timing belt, and calibrating the machine over time and when the temperature changes significantly.

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    What resolution and level of repeatability can one usually expect from a kit-built cnc, and is there a significant difference between timing belt and chain drive systems?

  • Can you have interchangeable heads between plasma and milling head on same machine

    Yes, you can simply disengage the spindle mount or z-axis assembly, and engage a plasma mount. There are many variables, however, depending on the machine.

    Additional Information:
    Thanks for the reply is there a preferred size table for the plasma milling option

    Additional Information:
    The size of the plasma or milling table will depend on how you apply the machine and what size sheet material you plan on cutting and milling. For the plasma work, remember to position a non flammable substance below where the plasma nozzle will be spraying. The particles ejected from the work-piece caused by the cutting action of the plasma nozzle can ignite flammable materials.

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    Can you have interchangeable heads between plasma and milling head on same machine