General > General Technical Chat
Can a HackRF One be used to measure safe/unsafe levels of EMF?
jonpaul:
Hello:
Kindly suggest that you research and learn the technology before you buy anything.
SDR: Hack One reviews, vs the Leo Bodnar SDR Play https://www.sdrplay.com
Antennas and sensor: The spectrum analyzer or SDR is just a reciever and the transducer r antenna affects the sensitivity, bandwidth, directionality.
EMC probes and EMC antennas are a huge topic. The analyzer or SDR without the selected antenna is useless.
"safe/unsafe levels of EMF"
Huge topic, and somewhat controversial and politically affected.
The field intensity and bands are in FCC, WHO, CE regulations, for every radio band.
Are you interested in WiFi, GSM, 5G, 4G 3G mobile, microwave ovens, high voltage transmission lines?
Each needs a different analyzer and antenna! Each has different intensity specs.
In short this is a huge field even for the government regulators and equipment manufacturers.
Dont expect reliable data from a cheap Chinese spectrum analyzer or SRD, without calibration and a calibrated antenna.
Bon Chance,
Jon
Frequint:
Hi, I know of these guidelines, perhaps not up-to-date but they give a good indication I think.
https://europaem.eu/attachments/article/124/EUROPAEM_EMF_Guideline_2016_English_Original.pdf
Pg 17 & 18.
Hope its help full :)
TimFox:
Note that there are two quite different parameters:
When you hold the phone up to your head, you are in the "near field" region, where there is no radiation, but energy is stored in the local field. The effect of this is measured in "SAR", which is the rate at which you absorb energy from the oscillating RF field. Regulations give maximum allowable safe levels of this parameter, but muckraking articles in responsible media have found that some phones (measured in a qualified testing lab) did exceed the legal limit.
When you are many wavelengths away from a cellular tower or high-power broadcast station, you are now in the "radiation field" region, and the RF power is radiating past you. This falls off as inverse-square of the distance.
With 60 Hz AC, the wavelength at the low frequency is extremely long, and you will always be in the "near field" region, as in the example above of a mis-wired room where the wiring forms a loop around you. (I encountered such a loop once when my in-laws asked me to fix a light switch in an old house.)
El Rubio:
--- Quote from: TimFox on March 15, 2022, 08:30:52 pm ---Note that there are two quite different parameters:
When you hold the phone up to your head, you are in the "near field" region, where there is no radiation, but energy is stored in the local field. The effect of this is measured in "SAR", which is the rate at which you absorb energy from the oscillating RF field. Regulations give maximum allowable safe levels of this parameter, but muckraking articles in responsible media have found that some phones (measured in a qualified testing lab) did exceed the legal limit.
When you are many wavelengths away from a cellular tower or high-power broadcast station, you are now in the "radiation field" region, and the RF power is radiating past you. This falls off as inverse-square of the distance.
With 60 Hz AC, the wavelength at the low frequency is extremely long, and you will always be in the "near field" region, as in the example above of a mis-wired room where the wiring forms a loop around you. (I encountered such a loop once when my in-laws asked me to fix a light switch in an old house.)
--- End quote ---
Maybe you mistyped, but there is absolutely RF radiation in the near field of a transmitting antenna. Also, farther away, the RF power is not necessarily radiating "past you". If you, or part of you, is resonant, that part will absorb the RF it is exposed to. I don't mean to critique your post, but I'm also confused by your description of the 60Hz loop from household electrical wiring. Can you explain that and what you experienced?
TimFox:
In the near field of a transmitting antenna, the predominant effect is the energy "stored" in the oscillating (not radiating) field. "Past you" was just a description of the direction. A conductive object (like the saline in the human body) will absorb energy from either of these fields. If the dimensions of the object are a resonant condition at that frequency, the absorption will be enhanced.
The wiring error I mentioned was using two SPDT ("three-way") switches to control a ceiling light, where a wire went from the common contact of one switch to the ceiling fixture and then to the common contact of the other switch. At each end, the fixed contacts were connected to line and neutral. This formed a loop, but I was not worried about the AC field. The real problem was that the switches tended to "make" just before "break", giving a temporary short between line and neutral, eroding the switch contacts.
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