Machine Recycling Discussion and Moderated Newsgroup > Parts Machines
> Diesel Powered
> West
> New
> New cell phone & tower rf/microwave radiation meter,
New cell phone & tower rf/microwave radiation meter,
CELL PHONE & TOWER RF/MICROWAVE RADIATION METER
Professional Meter to Measure Microwaves & Radio Frenquencies
As emitted by Cellular Communications & Data Systems
Brand New Equipment, Latest Model
With the growth of the cell phone industry, and widespread use of cellular telephones, have come numerous complaints and even epidemiological studies claiming the low-level microwave radiation emitted by these devices are harmful to human health. Low level microwave radio frequenices (RF) are given off not only by the cell phones, but also by repeater stations placed on the roofs of apartment buildings (to eliminate "dark zones" where cell phones might otherwise be unusable), as well as from larger cellular telephone and microwave communications towers. Obtaining precise measurements of the radiations from these various devices and antennas has always posed a big problem for those wanting to have exacting information on their exposure levels.
The new Cell Phone and Tower RF Radiation Meter is designed to measure frequencies within two ranges (1 GHz or "gigahertz" = 1000 MHz or "megahertz"):
1) the range of cell phones and towers specifically (0.8 - 1.7 GHz), and
2) a broader range which encompasses cell phones, towers and other microwave exposures such as microwave ovens (which yield an emission peaking at around 2 GHz), in addition to radiofrequencies as from AM radio broadcasting towers (0.5 MHz - 3 GHz).
If you only want to measure high frequencies such as cell phones and cell phone towers, switch the Bandwidth to "Narrow". To see all microwave and radiofrequencies, switch to "Wide". An instruction sheet is included.
A selector switch allows detection in three ranges of intensity, which span from .001 to 2000 microwatts/cm2. Signal strengths may rapidly fluctuate in these frequencies, so there is a slow-fast selector switch, to smooth out the readings. The meter also now has a self-adjustment feature for zeroing and temperature-compensation, replacing an older model which required manual adjustments. It also has a low-battery indicator, and is fully portable, using only a 9-volt battery. You simply turn it on, set to the sensitivity range desired, and then to wide or narrow bandwidth for evaluation of the RF-microwave sources you wish to measure, as noted above in points 1) and 2).
See the note below on "How Do You Know What Exposure Levels Are Safe?"
To Operate, turn the left knob clockwise to the desired sensitivity range - to 19.999 for the most sensitive, or 1999.9 for the least sensitive scales as when exposing the meter to stronger sources.
If you only want to measure high frequencies such as cell towers and microwave ovens, switch "Bandwidth" to "Narrow". To see all RF frequencies, switch to "Wide". Make sure your hand is not blocking the top third of the meter as this can reduce the readings. The sensor is in the top-front of the meter and the meter should be held vertically upward (it measures the vertical electrical field component of the RF wave and converts that number to a power density on the display).
Because your body (and other objects) reflect radio waves, there is some ambiguity in the readings. This is especially true at the higher frequencies. You'll notice that if you first measure and then reduce the distance from your body to the meter by one inch, the reading may change. Also, as you move the meter, the reading may repeatedly go higher-lower-higher every inch or so. You should take an average in this case. Generally, the RF waves have most of their power in the vertical electrical field, but some is in the horizontal. To get a true measurement of the total RF power density propagating toward you, hold the meter vertical (with the battery-lid side facing the object you are testing) and read that number. Then turn the meter horizontal (either 90 deg. left or right of vertical, with the back still facing the object you are testing) and add that number to the vertical reading. This gives the sum of vertical and horizontal power density.
This meter uses a standard 9-volt battery (included) and has a low battery indicator on the display. Battery life is typically 3 hours of measurement time. If LOW BATTERY shows on the display, you have about 15 minutes of battery life left. Slide the back lid off (in a direction away from the 2 screws) and replace the 9 volt battery.
Additional Technical Details From the Engineer:
Technically a "power density" meter, the "Cell Phone Meter", or RF (radio frequency) Field Strength Meter detects the electric field of radio and microwaves (RF) from .5 MHz to 3 GHz, and expresses the field strength as power density (.001 to 2000 microwatts/cm2).
This is an extremely sensitive meter which can accurately measure RF background even in rural areas far from any transmitters. The meter reads true power density directly on the display. Unlike other low-cost field strength meters, this meter's frequency response does not depend on the characteristics of an external antenna; the internal detection system yields a flat response over a very wide range of frequencies.
A High-Pass selector switch allows you to measure either the full bandwidth ("Wide" = 0.5 MHz - 3 GHz) or to apply a high-pass filter ("Narrow" = 6 dB/ octive rolloff with a knee at 100 MHz) that effectively allows only 100 MHz to 3 GHz through. In practice, this high-pass selector function can be used to estimate one additional parameter: the average frequency of the RF (if it is in the range 10 MHz - 500 MHz). The Bandwidth highpass function allows through only the high frequencies such as cell towers. At the "Wide" bandwidth, all frequencies down to .5 MHz are allowed, including AM radio.
The RF Field Strength Meter is directional and it detects only the component of the electric field which has the same polarization as the long axis of the meter. That is, if only a vertically-polarized RF wave is present, but you turn the meter in the horizontal direction, it will essentially read zero. If you subsequently rotate the meter to vertical, it will then read the full power density of the RF wave. Most RF radiation has only vertical electric field, so the full strength can be read by holding the meter vertically. (At the end of this page is more information on how to read radio waves with other polarizations).
The meter has a 4 1/2 digit display which reads in three ranges: .001 to 19.999, .01 to 199.99, and .1 to 1999.9 microwatts/cm2. For comparison, a low power 100 milliwatt dipole transmitter (typical 49 MHz cordless phone) produces about .010 microwatts/cm2 at a distance of 50 feet. This is 10x the minimum sensitivity of the meter. A FAST/SLOW update switch is normally set in the FAST position so you can quickly measure changes in the RF level. However, if the field strength is fluctuating rapidly, this switch can be set to the SLOW position, which averages the reading over several seconds.
[The following goes into more detail about using the meter to estimate the average frequency of an RF signal, and also the directionality of RF measurements.]
When measuring an RF signal of unknown frequency, you may notice that the reading is different when the Bandwidth switch is set to "Wide" vs. "Narrow". If so, you can estimate the average frequency (averaged over the power density) of the RF spectrum. If it's just a wave of a single frequency, you can estimate the frequency of that wave.
This estimate is done by measuring the power density with the Bandwidth switch set at "Wide", and then measuring the power density with the switch set to "Narrow". If these numbers are the same, the average frequency is above 500 MHz. If the "Narrow" number is less than 1% of the "Wide" number, then the average frequency is below 10 MHz. If the "Narrow" number is between about 1% and 96% of the "Wide" number, you can estimate average frequency from the ratio of the two numbers. (A written table is in the instructions).
Although most commercial RF transmitters radiate with a vertical antenna and thus a vertical electric field (so you can hold the meter vertically to measure the full power density), some RF radiation also has some horizontal component, due to reflections or transmitters that have antennas not pointed vertical. If you know where the transmitter is, you will only have to perform two readings to find the transmitter's total power density at your position. These correspond to "Z" (vertical) and "X" (horizontal, but perpendicular to the direction of the transmitter). In theory, if you point the meter's long axis toward the antenna (the "Y" direction), you will not detect any radiation from that antenna. This seems counterintuitive. (In fact, there may be some diagonal reflectors near you that produce a small "Y" component coming from the transmitter, but this is not usually significant).
In practice, if the back face of the meter is facing the RF source, and the meter is read first in the vertical orientation and then it is read after being rotated 90 to the horizontal position (with the back face still facing the RF source), the sum of those two numbers will be the true power density from that transmitter. (This addition is a "sum of squares". That is, because power density is proportional to the square of the electric field, then the direct sum of these two numbers, and not the square root of the direct sum, will be the correct magnitude of the power density.) Most RF field sources are principally vertically polarized, in which case only the vertical reading needs to be done. To measure the full power density at a certain point in space, regardless of the sources' locations, measure the vertical first (meter pointed upward). This will usually be the majority of the RF power density. Then make two measurements 90 apart, with the meter's long axis pointed in the horizontal direction. For example, after the vertical measurement, measure holding the meter in a north-south orientation and then in an east-west orientation. The sum of these three numbers is the total power density at that point in space, regardless of the position of the transmitter or transmitters. An accuracy problem arises however, because your body can block RF radiation, so if an unseen transmitter is located on the opposite side of your body from the meter, the reading will be falsely low. If you hold the meter higher than your head, this problem disappears. The presence of your hand and arm will have some effect on the field strength at the meter, so the most accurate reading is taken by setting the meter on a non-metallic surface or using, for example, a plastic holder.
This meter measures the power density of radiowaves from .5 MHz to 3000 MHz (3 GHz). Accuracy in the FM, TV and cell tower frequency range (30 MHz - 2.4 GHz) is +/-25%. Sensitivity is low by 50% (-3 dB) at the frequency limits .5 MHz and 3 GHz. (Sensitivity is 25% at 5 GHz. That is, you must multiply the reading by 4 when measuring microwaves at that high a frequency. At 10 GHz, sensitivity is about 10%.)
CLICK HERE for our special informative webpage on:
How Do You Know What Exposure Levels Are Safe?
and from our larger catalog homepage.
No State Sales Tax ever from our facility in the Oregon Mountains! Save from 3% to 10%!
