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I use a Raspberry Pi for transmitting FM on 107.9 Mhz.

It uses square waves and has a power of approx 0.085 Watts, but just to be safe:

If I have a 1 watt transmitter approximately 1 metre away from me whilst I'm sleeping, does this pose ANY risks?

I know there's a lot of confusion about electromagnetic waves and dangers.

As far as I'm aware, I do not have electromagnetic hypersensitivity (I think I would know if I did).

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    $\begingroup$ so, what are you asking then? Health risks of a 1W emitter? Health risks of a 85 mW emitter? Your question is a bit broad. And generally: the now 30 years of billion-specimen experiment with cellular phones that can emit up to 1W in a proximity much closer than 1m has not led to a statistically measurable increase in health problems due to interaction with radio waves, so wherever your "confusion" comes from: Put it back there, and leave it alone as unfounded. $\endgroup$ – Marcus Müller Nov 4 '17 at 9:54
  • $\begingroup$ Just to confirm i am asking about health risks of a 1W transmitter, hence the question mark there. $\endgroup$ – Niall Nov 4 '17 at 9:56
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    $\begingroup$ The website Amateur Radio RF Safety Calculator can help calculate safe RF levels for various frequencies. The website uses formulas based on FCC guidelines. It requires knowing a bit more about the setup than you have provided in your question, but some reasonable assumptions can be made. Assuming: - 1 watt RMS power - 100% duty cycle (meaning % time the radio is actually transmitting) - Antenna gain no better than a common dipole - A distance of 3 feet - Frequency of 107.9 MHz The setup is in compliance with FCC guidelines. In fact, for an "uncontrolle $\endgroup$ – Adam KC0DAD Nov 6 '17 at 16:05
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    $\begingroup$ If you are transmitting 85 mW square waves at 107.9 MHz, you are in danger of violating FCC regulations (and likely the RF regulations of many other countries, if instead located there) with the harmonic splatter due to sending unfiltered digital outputs to an antenna. Either insert a suitable bandpass filter on the Rasberry Pi's output, or only transmit into a reasonably shielded dummy load. $\endgroup$ – hotpaw2 Nov 15 '17 at 18:28
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    $\begingroup$ Users of this device might want to confirm that, if this transmit system is covered by FCC Part 15 for unlicensed use in the FM broadcast band, it does not radiate more than 250 µV/m in any direction 3 meters away from its antenna. That field can be produce by a center-fed, 1/2-wave dipole radiating only 11.43 nanowatts (0.000 000 011 43.. watts). See 47CFR §15.239. $\endgroup$ – Richard Fry Nov 16 '17 at 15:17
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Electromagnetic hypersensitivity does not exist. There is no confusion. It has been rigorously refuted by science.

One watt is orders of magnitude below safe exposure limits, and indeed probably less than exposure you are likely to get from cell phones, commercial broadcast stations, WiFi, and unintentional radiation from all kinds of electronics.

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    $\begingroup$ "Electromagnetic hypersensitivity does not exist." Sure it does! It exists in the minds of gullible people who've read too many websites claiming that it does. ;-) $\endgroup$ – Mike Waters Nov 16 '17 at 17:29
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The website Amateur Radio RF Safety Calculator can help calculate safe RF levels for various frequencies. The website uses formulas based on FCC guidelines. It requires knowing a bit more about the setup than you have provided in your question, but some reasonable assumptions can be made. Assuming:

  • 1 watt RMS power
  • 100% duty cycle (meaning % time the radio is actually transmitting)
  • Antenna gain no better than a common dipole
  • A distance of 3 feet
  • Frequency of 107.9 MHz

The setup is in compliance with FCC guidelines. In fact, for an "uncontrolled" environment (where no special consideration is made) you can get as close as roughly 1.4 feet.

Based on the frequency, I'm going to guess you are transmitting an FM signal. The FM mode has a 100% duty cycle when you are transmitting. If you were using another mode you would adjust the average power input by the duty cycle. The link above has details on this process at the bottom of the page.

The FCC guidelines (and as a result, the calculations on this website) are rather conservative. I probably wouldn't strap it to my head, but I wouldn't worry about it being on my night-stand.

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    $\begingroup$ "The FM mode has a duty cycle much less than 100%" How do you figure? "I probably wouldn't strap it to my head" but you'd hold a cell phone to your head? $\endgroup$ – Phil Frost - W8II Nov 6 '17 at 16:41
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    $\begingroup$ My apologies. FM is 100%. I've spent too much time figuring SSB lately. I'm editing the answer. $\endgroup$ – Adam KC0DAD Nov 6 '17 at 19:42

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