Which RF energy source would be more deadly to the human body?
ScottH, Wed Mar 15 2017, 02:05PM1,000,000 watts @ 550 KHZ or 100,000 watts @ 100 MHZ? Lets assume a radio tower tech was working right next to a fully energized antenna on top of the mast.
Does the frequency make much of a difference? What about 10,000,000 watts @ 10 KHZ vs the other 2? I know RF heats the body, but how does the frequency play into it?
Re: Which RF energy source would be more deadly to the human body?
KrowBar, Wed Mar 15 2017, 05:52PM
The question is not particularly clear. When you refer to power levels are you talking about the TPO, the ERP, the consumed power? The frequency could certainly make all the difference. Firstly, consider that if the frequency is closer to the body's resonance, then much more of the radiated power will be absorbed. Secondly, consider that the frequency coupled with the geometry of all the surroundings will have a huge effect on the local power density. The power radiated by an antenna isn't really the parameter of interest here - it is the power density in the space occupied by the person. Think of it like being in a microwave oven (pretty much the same thing really) where you will have hot spots and cold spots that all depend on the little details and that will change with the frequency. Further, the orientation between the E-field and H-field will be quite complex in the nearfield region and the resulting effective power density field will be quite non-uniform so it's impossible to analyze without a very detailed simulation.
I think the question you are trying to ask is something along the lines of "Is is worse to stand in a 10 W/cm^2 500 kHz 'beam' or a 1 W/cm^2 100MHz 'beam'?"
In that case I think the lower power 100 MHz wave is more damaging. As an antenna, the human body is pretty well tuned to very near 100 MHz. We just aren't tall enough to effectively pick up low frequencies in the kHz or even 100 kHz range. I would expect the SAR of the 100 MHz case to be maybe 5 orders of magnitude higher for a given power density. Plugging in some numbers (assume 0.3 W/kg per mW/cm^2 @ 100MHz and 0.00001 W/kg per mW/cm^2 @ 500 kHz) you get heating of 300 W/kg for the 1W/cm^2 100MHz case and 0.1 W/kg for the 10W/cm^2 500kHz case. Neither one would be good for you, but the former would cook all the meat in your body to well-done temperatures within a matter of minutes.
KrowBar, Wed Mar 15 2017, 05:52PM
The question is not particularly clear. When you refer to power levels are you talking about the TPO, the ERP, the consumed power? The frequency could certainly make all the difference. Firstly, consider that if the frequency is closer to the body's resonance, then much more of the radiated power will be absorbed. Secondly, consider that the frequency coupled with the geometry of all the surroundings will have a huge effect on the local power density. The power radiated by an antenna isn't really the parameter of interest here - it is the power density in the space occupied by the person. Think of it like being in a microwave oven (pretty much the same thing really) where you will have hot spots and cold spots that all depend on the little details and that will change with the frequency. Further, the orientation between the E-field and H-field will be quite complex in the nearfield region and the resulting effective power density field will be quite non-uniform so it's impossible to analyze without a very detailed simulation.
I think the question you are trying to ask is something along the lines of "Is is worse to stand in a 10 W/cm^2 500 kHz 'beam' or a 1 W/cm^2 100MHz 'beam'?"
In that case I think the lower power 100 MHz wave is more damaging. As an antenna, the human body is pretty well tuned to very near 100 MHz. We just aren't tall enough to effectively pick up low frequencies in the kHz or even 100 kHz range. I would expect the SAR of the 100 MHz case to be maybe 5 orders of magnitude higher for a given power density. Plugging in some numbers (assume 0.3 W/kg per mW/cm^2 @ 100MHz and 0.00001 W/kg per mW/cm^2 @ 500 kHz) you get heating of 300 W/kg for the 1W/cm^2 100MHz case and 0.1 W/kg for the 10W/cm^2 500kHz case. Neither one would be good for you, but the former would cook all the meat in your body to well-done temperatures within a matter of minutes.
Re: Which RF energy source would be more deadly to the human body?
ScottH, Wed Mar 15 2017, 11:15PM
In a electromagnetic field, does the electric field and the magnetic field affect the body differently? Does the electric field cook you more or the magnetic component?
ScottH, Wed Mar 15 2017, 11:15PM
KrowBar wrote ...
The question is not particularly clear. When you refer to power levels are you talking about the TPO, the ERP, the consumed power? The frequency could certainly make all the difference. Firstly, consider that if the frequency is closer to the body's resonance, then much more of the radiated power will be absorbed. Secondly, consider that the frequency coupled with the geometry of all the surroundings will have a huge effect on the local power density. The power radiated by an antenna isn't really the parameter of interest here - it is the power density in the space occupied by the person. Think of it like being in a microwave oven (pretty much the same thing really) where you will have hot spots and cold spots that all depend on the little details and that will change with the frequency. Further, the orientation between the E-field and H-field will be quite complex in the nearfield region and the resulting effective power density field will be quite non-uniform so it's impossible to analyze without a very detailed simulation.
I think the question you are trying to ask is something along the lines of "Is is worse to stand in a 10 W/cm^2 500 kHz 'beam' or a 1 W/cm^2 100MHz 'beam'?"
In that case I think the lower power 100 MHz wave is more damaging. As an antenna, the human body is pretty well tuned to very near 100 MHz. We just aren't tall enough to effectively pick up low frequencies in the kHz or even 100 kHz range. I would expect the SAR of the 100 MHz case to be maybe 5 orders of magnitude higher for a given power density. Plugging in some numbers (assume 0.3 W/kg per mW/cm^2 @ 100MHz and 0.00001 W/kg per mW/cm^2 @ 500 kHz) you get heating of 300 W/kg for the 1W/cm^2 100MHz case and 0.1 W/kg for the 10W/cm^2 500kHz case. Neither one would be good for you, but the former would cook all the meat in your body to well-done temperatures within a matter of minutes.
The question is not particularly clear. When you refer to power levels are you talking about the TPO, the ERP, the consumed power? The frequency could certainly make all the difference. Firstly, consider that if the frequency is closer to the body's resonance, then much more of the radiated power will be absorbed. Secondly, consider that the frequency coupled with the geometry of all the surroundings will have a huge effect on the local power density. The power radiated by an antenna isn't really the parameter of interest here - it is the power density in the space occupied by the person. Think of it like being in a microwave oven (pretty much the same thing really) where you will have hot spots and cold spots that all depend on the little details and that will change with the frequency. Further, the orientation between the E-field and H-field will be quite complex in the nearfield region and the resulting effective power density field will be quite non-uniform so it's impossible to analyze without a very detailed simulation.
I think the question you are trying to ask is something along the lines of "Is is worse to stand in a 10 W/cm^2 500 kHz 'beam' or a 1 W/cm^2 100MHz 'beam'?"
In that case I think the lower power 100 MHz wave is more damaging. As an antenna, the human body is pretty well tuned to very near 100 MHz. We just aren't tall enough to effectively pick up low frequencies in the kHz or even 100 kHz range. I would expect the SAR of the 100 MHz case to be maybe 5 orders of magnitude higher for a given power density. Plugging in some numbers (assume 0.3 W/kg per mW/cm^2 @ 100MHz and 0.00001 W/kg per mW/cm^2 @ 500 kHz) you get heating of 300 W/kg for the 1W/cm^2 100MHz case and 0.1 W/kg for the 10W/cm^2 500kHz case. Neither one would be good for you, but the former would cook all the meat in your body to well-done temperatures within a matter of minutes.
In a electromagnetic field, does the electric field and the magnetic field affect the body differently? Does the electric field cook you more or the magnetic component?
Re: Which RF energy source would be more deadly to the human body?
KrowBar, Thu Mar 16 2017, 03:26PM
Hmmm. I don't have the biology background to know which is more problematic. For planer waves in the far field there is a well defined relationship between the E and H fields - you can't have one without the other, and the combined electromagnetic field transfers energy to the body (receiver antenna) which causes the cooking. Static fields are another story entirely and I'm sure there have been studies on the effects of each. A static electric field makes your hair stand on end, while a static magnetic can make you levitate:
KrowBar, Thu Mar 16 2017, 03:26PM
Hmmm. I don't have the biology background to know which is more problematic. For planer waves in the far field there is a well defined relationship between the E and H fields - you can't have one without the other, and the combined electromagnetic field transfers energy to the body (receiver antenna) which causes the cooking. Static fields are another story entirely and I'm sure there have been studies on the effects of each. A static electric field makes your hair stand on end, while a static magnetic can make you levitate:
Re: Which RF energy source would be more deadly to the human body?
radiotech, Tue Jun 20 2017, 09:37PM
Amateur Radio Operators in Canada are required to study Limits of Human Exposure to
Radio Frequency Electromagnet Fields from 3 kHz to 300 GHz.
You should get your own Ham ticket.
Then you could talk, on your own radio, to a wide body of peers who know first hand about radio frequency.
radiotech, Tue Jun 20 2017, 09:37PM
Amateur Radio Operators in Canada are required to study Limits of Human Exposure to
Radio Frequency Electromagnet Fields from 3 kHz to 300 GHz.
You should get your own Ham ticket.
Then you could talk, on your own radio, to a wide body of peers who know first hand about radio frequency.
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