RF Electrosmog Sensor (Product No. 3159) Range 1: 0 to 100.00 % Range 2: -60.00 to 0 dBm Range 3: 0 to 6 V/m
Data Harvest Group Ltd. 1 Eden Court, Leighton Buzzard, Beds, LU7 4FY Tel: 01525 373666 Fax: 01525 851638 e-mail: sales@data-harvest.co.uk www.data-harvest.co.uk
DS 096
Data Harvest. Freely photocopiable for use within the purchasers establishment
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RF Electrosmog Contents Introduction ................................................................................................................................ 2 What is Electrosmog? ................................................................................................................ 2 Connecting................................................................................................................................. 3 Ranges ...................................................................................................................................... 3 Aerials /Antenna ........................................................................................................................ 4 Making an aerial /antenna ......................................................................................................... 5 Calculation of aerial length ................................................................................................... 5 To fit the supplied F plug to the coaxial cable ...................................................................... 6 Simple Monopole antenna .................................................................................................... 7 Simple Dipole antenna ......................................................................................................... 8 Units and terms.......................................................................................................................... 8 Practical information .................................................................................................................. 9 Investigations ........................................................................................................................... 10 Recording background activity ........................................................................................... 11 Recording mobile phone activity ........................................................................................ 12 Limited warranty ...................................................................................................................... 14
Introduction The Smart Q RF Electrosmog detector is a broadband width RF detector. It can detect radio frequency waves/fields (RF) over the frequency range of 50 MHz to 3 GHz. This means it is suitable for measuring the RF that comes from Bluetooth, WiFi, microwave ovens and mobile phones. The detector does not distinguish the frequency of the RF source; some discrimination of frequency can be achieved with design of the antenna. The RF Electrosmog detector is fitted with a female F type connector (the type of connector used for cable and satellite aerial connections). The F - type connector allows the user to make and attach antennae that are more specifically tuned to a particular frequency. The sensor is supplied with:
One antenna (ANT1) cut to 32.5 mm, the ¼ wavelength of 1.8 GHz (mobile phone frequency).
A 0.5 metre length of coaxial cable.
2 screw on F connectors for making your own aerials
What is Electrosmog? Electrosmog is a term applied to the background, invisible, electromagnetic radiation resulting from the use of both wireless technology and mains electricity. Common sources of RF Electrosmog are:
Cordless phones (e.g. DECT mobile landline)
Mobile/cellular phone masts/towers/transmitters
Mobile/cellular phones
Wireless networks e.g. WiFi.
T.V. senders
Remote controls e.g. for cars, alarm systems, opening gates
Cordless baby monitors
There have been concerns expressed that electromagnetic radiation in the environment has a health impact. A brief look on the internet will show that there is no real consensus. Official
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RF Electrosmog bodies provide evidence that there is no need to be concerned, while environmental bodies indicate that there is a problem. The real risk is difficult to identify, and may be non existent. Current advice is to use caution, but not to be over concerned; other risks may be considerably more significant. What we do need to be careful about, is that we are not cherry picking the risk to justify our concerns in another area. For example, are concerns about mobile masts really about RF or are they about the visual or financial cost of a mast at the bottom of a garden. After all how many individuals that show concern still use their mobile phone, cordless phones, the internet over WiFi, lock and unlock the car, all of which use RF, in their campaign to ban a source of RF?.
Disclaimer
!
The Smart Q Electrosmog RF detector is sold for the purpose of teaching and educational instruction. It is not, and has not been designed to be an RF monitoring tool. The results are illustrative only; any information gained from the use of this apparatus must not be used as the basis for any health and safety audit or diagnosis.
Connecting
Push one end of the sensor cable (supplied with the EASYSENSE unit) into the hooded socket on the detector.
Connect the other end of the sensor cable to an input socket on the EASYSENSE unit
The EASYSENSE unit will detect that the RF Electrosmog detector is connected and display values using the currently selected range
The supplied antenna (ANT1) screws onto the threaded connector on the sensor body. Make sure the copper centre wire of the antenna that projects slightly is aligned with the centre hole of the connector. The connector contains a pair of sprung jaws to grip the centre wire of the antenna, so a slight force is needed to push the wire through the jaws. Tighten the antenna onto the connector finger tight only.
Ranges The RF Electrosmog detector has three ranges. 1.
Decibels (dBm) - dBm is a common measure of RF activity. It references the received signal to a known 1 mW level. This is a log scale; small numerical changes may represent large changes in power measured. Every 3 dBm of change represents a doubling or halving of power.
2.
Volts per metre (V/m) – is used to measure electric field strength. This is a linear scale. Most devices will produce small V/m values. Mobile phones produce a peak V/m values of about 2.5 V/m. DECT cordless phones can produce higher values (values of 5 V/m have been recorded in testing).
3.
Percentage (%) – gives the user a simple comparative scale of RF. This scale is based upon the dBm scale but displayed in percentage units to make them more intuitive.
With some EASYSENSE units it is possible to set the range from the unit. Please refer to the EASYSENSE unit’s user manual. To alter the range in the EasySense software: 1. Select EasyLog from the Home screen.
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RF Electrosmog 2. 3. 4. 5. Or 1. 2. 3. 4.
Select the New recording wizard icon. Click on the sensor’s name. A set sensor range window will open. Select the required range, then OK. Select Finish to exit the wizard. From the Home screen select Sensor Config from the Settings menu. Select the Electrosmog sensor from the list and click on the Change Range button. The current range will be highlighted. Select the required range and click on OK. Close Sensor Config.
The range setting will be retained until changed by the user.
Aerials /Antenna Antenna /aerial are interchangeable terms for the same object. In the American English speaking world the term antenna is used, in the British English speaking world the term aerial is used. Radio engineers may be more precise and describe an antenna as a rigid device and an aerial as made of flexible wire. Historically, Marconi used antenna, it is an Italian word to describe a supporting pole – he used a tent pole for his early work! An antenna / aerial works by collecting RF energy. RF energy vibrates with a frequency and if the aerial is matched (by length) to the wavelength of the RF, it will start to resonate with the frequency of the RF signal. The resonance will create a standing wave of voltage (potential difference, p.d.) on the aerial. The length of aerial to create the biggest potential difference is ¼ λ. A change in length will tend to reduce the p.d. (a 10% variance in the correct length can create a 25% reduction in aerial signal). The design of the aerial tries to achieve the position where the highest part of the standing wave is at one end of the aerial and the lowest part of the standing wave is at the other end. This creates a maximum potential difference on the aerial. The change in the p.d. due to modulation of the original signal is picked up the RF Electrosmog detector and amplified to recreate the original broadcast information.
A monopole aerial is a type of radio aerial formed by using an active antenna element of a ¼ wavelength with a ground plane at right-angles to it. If the ground plane is large enough, the monopole behaves like a dipole (as if its reflection in the ground plane forms the missing half of the dipole). When used for radio broadcasting, the radio frequency power from a broadcasting transmitter is fed across an insulator between the active aerial element and the ground plane. For AM broadcasts large bundles of copper wires, at least ¼ wavelengths long, are buried in the
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RF Electrosmog ground below the aerial. The ground below the aerial then becomes the ground plane of the aerial system. A monopole system will radiate RF energy in all directions from its surface. The long side of the aerial compared to its small cross section will give the radiated RF field a toroidal (doughnut- shaped) reception. In a WiFi or mobile phone the ground plane is created by a large patch of copper conductor on the circuit board of the transmitter module. A monopole aerial is used for these devices as it has little directionality (as a user you do not know the direction of the nearest base station). The RF will fall off in strength from the radiated source according to inverse square law (double distance ¼ energy). A dipole aerial is effectively 2 monopole aerials with one monopole connected to the transmitting circuitry and the other to the earth. Each half of the monopole is then “out of phase” with the other. This creates a doubling of the p.d. from resonance. Typically a dipole aerial is formed by two quarter wavelength conductors or elements placed back to back for a total length of λ/2. A standing wave on an element of a length ~ λ/4 yields the greatest voltage differential, as one end of the element is at a node while the other is at an anti-node of the wave. The larger the differential voltage, the greater the current flow between the elements. A dipole antenna should therefore be a better transmitter and receiver of the signal. The disadvantage is that the aerial has now become directional. If the receiving dipole is not in line with the signal, then the standing wave created will develop asynchronous nodes which will attenuate the signal
Making an aerial /antenna You will need wire of a minimum 1 mm diameter, preferably copper. If the diameter is too far from the recommended value in either direction it will either not make a good electrical connection inside the F-type connector or it will be difficult to fit and may damage the metal grips inside the connector. The diameter of the wire and the material it is made from will also affect the impedance of the antenna and alter its reception performance. The antenna should be ¼ of the wavelength of the main frequency to measure. There will be multiples of other frequency wavelengths in the antenna wire, but there will be peak discrimination to the desired wavelength. The antenna length is measured as the length of the wire exposed beyond the shielding / earth braiding of the coax cable Peak detection may be achieved for alternate frequencies by using aerials of different lengths.
Calculation of aerial length Antennas are most efficient when the wavelength (lambda) of the carrier is twice as long as the antenna. For a given frequency the wavelength can be calculated simply using the following formula:
λ = C/f λ = Wave length C = Speed of light (299,792,458 m/s) rounded up to 3 x 108 f = Frequency Divide your result by 4 to give the ¼ wavelength and thus the resonant antenna length: Adjustment of calculation when using coaxial cable In this calculation the value for the velocity of the wave has been given as the same as the velocity of light in a vacuum. However when light passes into a denser material than a vacuum, the velocity changes and the same applies for RF. The antenna is copper not a vacuum so a velocity change will take place. The exact change in velocity will depend upon the density of the material and the dielectric of the cable. You may notice that when
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RF Electrosmog investigating the effect of antenna length on signal strength that there is a difference between the peak signal antenna length by experiment and the calculated peak. The ratio of the experimental to that calculated as a percentage is the correction factor. The supplied coaxial cable has a published correction factor of 0.78, i.e. the speed of the RF through this cable is 0.78 of its speed in a vacuum. Wavelength in a coaxial cable (λ) = V PC f Vp = velocity factor of propagation through coaxial cable (the speed at which an RF signal travels through a material compared to the speed the same signal travels through a vacuum) C = speed of light = 3 x 108 m-s f = frequency in Hz Note: 1 kHz = 1,000 Hz (1 x 103), 1 MHz = 1,000,000 Hz (1 x 106), 1GHz = 1,000,000,000 Hz (1 x 109 or 10 x 108).
Examples: (1) The frequency of a WiFi or a microwave is typically 2.4 GHz = 2,400,000,000 Hz (24 x 108 Hz). The velocity factor of the supplied coaxial cable is 78%. λ = 0.78 x 3 x 10 8 = 0.78 x 3 = 2.34 = 0.097 m = 97 mm 24 x 10 8 24 24 So the aerial lengt h for 2.4GHz WiFi or a microwave =
λ = 0.097 = 0.024 m (24 mm) 4 4
(2) DAB uses frequencies around 220 MHz (220 x 106 or 2.20 x 108), so the wavelength is: λ = 0.78 x 3 x 108 / 2.20 x 108 = 1.06 metres A typical DAB aerial will be half this length at 53 cm long, but when using the Smart Q RF detector, a ¼ wavelength is preferred, so for DAB this would be 26 cm (260 mm). (3) Mobile phone using a frequency of 1.8 GHz (1.8 x 109 or 18 x 108). λ = 0.78 x 3 x 108 / 18 x 108 = 0.13 metres = 130 mm For use with the Smart Q RF detector, a ¼ wavelength is preferred, so for a mobile phone this would be 32.5 mm (3.25 cm).
To fit the supplied F plug to the coaxial cable Prepare the cable as shown in the diagram, for twist on connectors the exposed braid will need to be folded back over the outer sheath. Depending on the manufacturer of the co axial cable there can be an insulating layer on the braid and shielding. Check, and if necessary carefully remove. Cut a length of the coax cable. About 30 mm for the F plug fitment
Aerial length (l)
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RF Electrosmog Remove about 12 mm of the outer plastic sheath to expose the copper braid (take care not to cut the copper braid). Separate the braided copper wires and push them back over the plastic outer sheath to expose the white plastic insulation. If the white plastic insulation has a covering of copper foil cut it off. Remove the end 6 mm of the white plastic insulation to expose 6 mm of the solid inner copper wire. Push the prepared cable into the longer knurled end of the F plug and twist the plug until the inner plastic insulating core is level with the metal rim inside the plug (the plug has to cut a thread onto the cable so expect to feel resistance - you may need grips). Cut off any exposed copper braid
When fitted the inner copper wire will extend past the plug by about 2 to 3 mm. Look into the end of the plug and check that no stray braid wires are shorting to the inner copper wire. For other F connectors refer to the manufacture’s data sheets for cutting dimensions and connection method. The antenna length is measured as the length of the copper wire exposed from the copper braid shielding / earth.
Simple Monopole antenna Use coaxial cable – ideally with a solid copper centre core, with a sheath of a metal foil and copper braiding Aerial length (l) F-plug with central wire core just proud
Copper wire core
Plastic outer sheath
Plastic insulation
1.
Cut a length of the coax cable (aerial length + about 30 mm extra for F-plug fitment + bit extra for trimming). Attach the F-plug and trim the central wire core just proud.
2.
At the aerial length + bit extra for trimming, strip back the plastic outer sheath and copper braid/foil to expose the plastic insulation. Note: It is best if the plastic insulation covering the centre core has not been removed.
3.
Cut the exposed central core to the correct aerial length.
4.
Screw the antenna onto the RF electrosmog detector.
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RF Electrosmog If the plastic insulation is damaged or removed in the preparation it will not affect the antenna’s performance. It will however leave an exposed spike that may need protecting. Make sure that the outer braiding does not contact any of the exposed inner wire core.
Simple Dipole antenna Use coaxial cable – ideally with a solid copper centre core, with a sheath of a metal foil and copper braiding. In reality you may find little difference in the types of coax cable available (this could make an investigation, is there a difference?) 1.
Cut a length of the coax cable (aerial length + about 30 mm extra for F-plug fitment + bit extra for trimming). Attach the F-plug and trim the central wire core just proud.
2.
At the aerial length + bit extra for trimming, strip back the outer plastic sheath but take care not to cut or damage the copper braiding.
Copper braiding
3.
4.
Separate the braided copper wires. Fold the braiding back and twist to form a ‘single’ wire. Discard any foil that may be present. If possible solder the braiding together.
Aerial length (2l)
Bend the central core (plastic insulation and copper wire) and the twisted braid to form a T shaped end (one end of the T = the twisted braid, the other end the central core). Make sure the braid and central core do not make contact.
Central core of copper wire and plastic insulation
Copper braid twisted together
5.
The length from the tip of the solid centre core to the tip of the twisted braid should be ½ wavelength of the main frequency to be measured. Trim as necessary, trying to keep each side an equal length. You may need to expose more of the braid to achieve this.
6.
Screw the antenna onto the RF electrosmog detector.
The length of the wire from Antenna to detector is not important, but long lengths (excess of 10 metres) will attenuate the signal.
Units and terms The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity) relative to a specified or implied reference level. Since it expresses a ratio of two (same unit) quantities, it is a dimensionless unit. A decibel is one tenth of a Bel (B).
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RF Electrosmog The decibel is useful for a wide variety of measurements in science and engineering. It has a number of advantages:
The ability to represent very large or small numbers on a familiar scale.
A logarithmic scaling that corresponds to the human perception of sound and light.
The ability to carry out multiplication of ratios by simple addition and subtraction.
The decibel is not an SI unit. However, following the SI convention, the d is lowercase, as it represents the SI prefix deci -, and the B is capitalized, as it is an abbreviation of a name derived unit (the Bel). The full name decibel follows the usual English capitalisation rules for a common noun. The decibel symbol is often qualified with a suffix, which indicates which reference quantity has been assumed. For example,dBm indicates that the reference quantity is one milliwatt. The practice of attaching a suffix in this way is widely followed. dBm is an abbreviation f or the power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW). For the Electrosmog RF detector 0 dBm would indicate a signal power of 1 mW at the antenna. The log of 2 is 0.3, so the log of ½ is -0.3. If you halve the power, you reduce the power by 3 dB. Halve it again (down to ¼ of the original power) and you reduce the level by another 3 dB. Each reduction of the power by 3 dB is equivalent to halving the power. A change of 9 dB is therefore an equivalent of 3 lots of 3 dB or 23 = 8 fold change. Attenuate means to reduce - attenuation of a signal is the loss of signal SNR = signal to noise ratio, it is the ratio of the signal strength to the average noise, the noise level would be defined as 1 (0 dB). The signal strength is how far the signal 'stands out' from the noise. In general, higher signal to noise is better; the signal is 'cleaner'. Volts per meter (V/m) is the standard unit of electric field strength. An electric field of 1 V/m is represented by a potential difference of 1 V existing between two points that are 1 m apart. Reduced to base SI units. Hz = number of complete cycles of a sine wave per second. It has the prefixes k, m and g to represent 1,000x, 1,000,00x and 1,000,000,000x.
Practical information The RF Electrosmog RF detector can detect electromagnetic radiation in the microwave to radio frequency range of 5 x 107 to 3 x 109. increasing Frequency (v) 1014
1012
IR
10-6
1010
108
Microwave
10-4
10-2
106
104
FM AM Radiowaves
100
102
102
100
v (Hz)
Long radio waves
104
106
108
increasing Wavelength (λ) Electrosmog Sensor detection range RF activity will be reduced (attenuated) by several factors:
Distance from source – this should follow the inverse square law.
Objects between the receiver and transmitter
Objects that may create reflections and set up interferences in the signal.
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λ (m)
RF Electrosmog
Weather conditions
A Faradays shield may block some RF activity e.g. a mobile phones or radios may have no reception inside an elevator. The cooking chamber of a microwave oven is a partial Faraday cage enclosure which prevents the microwaves from escaping into the environment. A good way of excluding RF background activity is to place the Electrosmog sensor and the device being tested within a Faradays shield e.g. a large cardboard box which has been completely covered by a conducting material such as aluminium foil. Make sure there are no gaps in the foil and push the foil covered opening flap shut during the recording. Details of frequencies, transmitter powers for main mobile service providers:
GSM 900 GSM 1800
Base station transmit frequency
Hand set transmit frequency
935 – 960 mHz
890 – 915 mHz
1805 – 1880 mHz
1710 – 1785 mHz
Peak hand set frequency power 2 watts 1 watt
Prime users in the UK BT Cellnet Vodafone Orange One2one
Investigations Background RF in different locations e.g. use a map and the Meter function on a logger to record RF at different locations. If enough data is collected you can attempt to create an RF contour map showing distribution of RF activity. RF from a mobile phone (e.g. switching on and off, sending and receiving a call) RF from WiFi, Bluetooth devices or other remote controls Effect of antenna length on activity recorded. There should be some discrimination of RF by wavelength, create antennae at WiFi, Mobile 1.8 and DAB frequencies to compare. Record activity of key fobs for locking and unlocking a car (this will not reveal any keycode information as sampling too slow.
RF pattern from a car key fob unlocking the doors
Identifying the location of an RF source. Use metal shields and or a dipole aerial
Identify the wavelength of an RF source by interference of reflected signal
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RF Electrosmog
Placing the detector in a Faraday cage
Can you attenuate RF in a location?
How does distance from the source affect RF intensity? (RF follows the inverse square law).
Can you find the best direction for a television aerial?
Can you make a directional aerial?
What happens when you use a cordless mouse or keyboard?
Recording background activity Check for any obvious sources of RF present in the locality e.g. WiFi access points, mobile phone masts, mobile phone users (you may need to explain features in the graph).
Using Scope
Connect the RF Electrosmog detector to the logger, the logger to the PC and start the EASYSENSE software.
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RF Electrosmog
Select Scope from the Home page.
Select the mode is Normal.
Click on the Start icon to begin.
If activity is present the trigger will let data be collected and you should see a series of traces being recorded. If not click through the Lower and Higher trigger channel buttons to alter the trigger value - when an appropriate trigger is selected you will see a series of traces being recorded.
After watching several traces you may want to alter the trigger level and or time base. When you are happy that the most suitable trigger and interval are set, click on Stop.
Select the trigger mode as Single Shot and click on Start to collect a set of data.
Note: Although you cannot overlay data with Scope a multi graph recording can be created using Merge with File (File menu) to merge a set of data with a previously saved file (provided they have both been recorded with the same time base and intersample time).
Using Graph to record 4 consecutive recordings of background RF. Note the regular peaks, this is probably due to the beacon call of a WiFi access point or a mobile phone system. Select Overlay if you’d like to record multiple patterns on one graph. From the Options icon select the correct Number of Graphs. Right click in each graph area and select to display one recording in each graph.
Recording mobile phone activity 1. Connect the aerial to the RF detector. Mount the sensor vertically, with the aerial pointing down to the bench top.
2. Position the phone on the bench about 10 cm from the tip of the aerial. If you intend to compare different phones mark the bench position so each phone is placed at the same point.
3. If there is a lot of background activity in the working area set up a metal shield box Using Scope
Start the EASYSENSE software and select Scope from the Home screen.
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RF Electrosmog
Select an interval of 20 ms (Roll Mode). Click on Start and switch on the phone - as soon as the switch on peak is visible click on Stop. Use this data to calculate the best value for the trigger.
Click on Faster to alter the duration to a minimum of 1 second (you may have to vary this according to the phone and network being used). Select Single Shot and the appropriate trigger level e.g. Duration 2.56s, Trigger when Electrosmog is Positive 40% with a 25% pretrigger.
Set the phone to off. Click on Start and turn the phone on. The trigger will allow you to capture a good portion of the start up chatter of the phone.
Use Save as to save the data.
Record phone activity when it is: a. Turning on b. Turning off c. Sending a call d. Receiving a call
Using Graph
Start the EASYSENSE software and select Graph from the Home screen.
From the logging wizard select a suitable Fast recording time and interval e.g. to record only ‘switch on’ try 200 ms with a 50 us interval or to record ‘switch on and start up chatter’ try 5 s with a 2 ms interval. Select a trigger and any pre-triggers e.g. Trigger when Electrosmog rises above 40% (or -40 dBm) with a 25% pre-trigger.
Set the phone to off. Click on Start and turn the phone on.
To record other phone activities on the same graph select Overlay and repeat.
Switch on and start up chatter using the % range
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RF Electrosmog
Switch on and start up chatter using the V/m range
Note: The peaks appear to be smaller using the V/m range. The same energy is being measured but % or dBm is a log scale, whereas V/m is a linear scale. Data could easily be misinterpreted as either being an indication of more or less energy. This is a valid teaching point, and shows how data can be manipulated to prove or dismiss a case. Unless the observer understands the scales used to present the data, it is really meaningless.
Limited warranty For information about the terms of the product warranty, see the Data Harvest website at: https://data-harvest.co.uk/warranty. Note: Data Harvest products are designed for educational use and are not intended for use in industrial, medical or commercial applications.
WEEE (Waste Electrical and Electronic Equipment) Legislation Data Harvest Group Ltd are fully compliant with WEEE legislation and are pleased to provide a disposal service for any of our products when their life expires. Simply return them to us clearly identified as ‘life expired’ and we will dispose of them for you.
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