NA -- RF Experts

Discussion in 'Technical Corner' started by JGoodish, Jan 20, 2017.

  1. JGoodish

    JGoodish Cleared for Takeoff

    Joined:
    Jun 10, 2006
    Messages:
    1,160
    Display Name:

    Display name:
    JGoodish
    For all the RF experts, what are your thoughts on the use of Bluetooth headphones or earbuds? Obviously, some aviation headsets are Bluetooth-enabled, and there seems to be quite a bit of so-called "data" (or perhaps just "conjecture") on the potential health effects of prolonged use of Bluetooth equipment essentially on the head or in the ears.

    I suspect that Bluetooth in particular is so low power that despite the microwave frequency, any risk is very low. However, RF behavior and its effects are not my areas of expertise, so I'd be interested in the opinions of those who are far more educated on the matter.


    JKG
     
  2. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

    Joined:
    Apr 1, 2007
    Messages:
    12,853
    Location:
    PUDBY
    Display Name:

    Display name:
    Richard Palm
    I don't have specific information on bluetooth, but I think the power level probably is very low, and I also believe that the FCC has standards for maximum allowable RF exposure.
     
  3. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Generally at the power levels and frequency utilized, it's considered non-ionizing radiation, and harmless by the scientists.

    That said, we once had X-Ray machines in shoe stores for kid's feet that all the scientists told us were safe, too.

    So. Don't walk around with a 2.4 GHz transmitter in your earlobe 24/7. Stick it in when you need it, and put it away when you don't.

    If they find out later it's going to kill you, there will be a nice class action lawsuit and you'll get a postcard that says your share is $6.84 as a credit on your next month's phone bill, and some law firm will make enough to buy all the partners a Maserati.
     
    RV10flyer and slacktide like this.
  4. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

    Joined:
    Apr 1, 2007
    Messages:
    12,853
    Location:
    PUDBY
    Display Name:

    Display name:
    Richard Palm
    I happen to think that scientists' and engineers' understanding of RF exposure issues has advanced quite a lot since those days. YMMV.
     
  5. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Sure. And their understanding of the next dumb thing that will kill people is always right around the corner. You realize we're only talking less than one generation ago, right?

    I'm no science denier at all, but my generation started life without seat belts because nobody needed those crazy things. My truck has "top of the line" drum brakes and is only 16 years old.

    People selling stuff will always put profits over safety. And your Bluetooth headset was made for $0.10 at the One Hung Low plant in Schenzen. Think some corners might have been cut from the original RF shielding design? Heh.

    I've given myself RF burns above 1 GHz and I stay out of the way of my own 10 GHz 3W transmitter and dish, focusing all that power. I'm not afraid of RF. But I respect it.

    Common sense says I don't leave a 2.4 GHz transmitter shoved in my ear canal an inch of soft tissue and bone from my brain, for hours every day, for no particularly good reason, just because some company sells lots of them.

    It also says I'm fine to put it on when I need it and use it for a little while. Or hold the 1.8 GHz transmitter (the phone) up to my head for the length of a phone call.

    Your microwave oven operates at roughly 2.4 GHz by exciting water molecules in things, including meat and tissue. It's just a lot more power focused into the center of a small faraday cage.

    Guess what your skull kinda acts like at those frequencies? Not to mention how corneas react to microwave RF... but cataract surgery has come a long way since I was a kid, so there's that.

    My grandmother was amongst the first people in the world to have a lens replaced surgically after ultrasonically destroying hers to fix that particular problem.
     
    wilkersk likes this.
  6. Shawn

    Shawn En-Route

    Joined:
    May 6, 2013
    Messages:
    2,708
    Location:
    Santa Cruz, CA
    Display Name:

    Display name:
    Shawn
    The government says it is safe...
     
  7. JGoodish

    JGoodish Cleared for Takeoff

    Joined:
    Jun 10, 2006
    Messages:
    1,160
    Display Name:

    Display name:
    JGoodish
    Yes, the government saying that it's okay makes me about as comfortable as taking the Polar Bear Plunge with a sub-zero wind chill.

    In fairness, I don't know that anyone is saying that cellular or BT RF exposure is "good," only that there's little to no evidence that it's "bad." I tend to agree with Nate here in that even if it isn't harmful, it almost certainly isn't helpful.

    It's interesting though that the electronics industry seems to be moving away from wired headsets/headphones and toward BT. The iPhone 7 (which I own) was maligned for having no headphone jack, but it wasn't the first and likely won't be the last smartphone to omit a wired headphone jack. I suppose that BT next to your head is better than higher-power cell phone RF, but using a BT headset for audio content could be of much longer duration than a phone call. I wonder for how much longer phones and PCs will continue to provide a wired audio-out option.


    JKG
     
  8. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    Bluetooth operates at around 2.4 GHz an at power level of about 2.5 milliwatts. You're in more danger of harming your hearing from turning them up full volume, than any adverse health effects from the radiation.

    GROL, ARRT(R,CT)
     
    Last edited: Jan 28, 2017
    gismo likes this.
  9. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

    Joined:
    Apr 1, 2007
    Messages:
    12,853
    Location:
    PUDBY
    Display Name:

    Display name:
    Richard Palm
  10. JGoodish

    JGoodish Cleared for Takeoff

    Joined:
    Jun 10, 2006
    Messages:
    1,160
    Display Name:

    Display name:
    JGoodish
    Maybe, but prove it for long-term continuous exposure.


    JKG
     
  11. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    Um, ....OK, long term continuous use of just about anything probably isn't that great for you. For example, running up and down stairs continuously will wear out your hips and knees. Washing your hands with soap continuously will cause contact dermatitis. Staring at computer screens continuously will give you a headache. ..... Speaking of which, peace out dude! Sheesh!
     
  12. JGoodish

    JGoodish Cleared for Takeoff

    Joined:
    Jun 10, 2006
    Messages:
    1,160
    Display Name:

    Display name:
    JGoodish
    Long-term continuous exposure is exactly what most folks would experience using BT headphones. I'm not aware of too many folks who listen to music or audio books for only a few minutes at a time. Therefore, while the risk of health issues from such use may be low, it's likely elevated versus using wired headphones.

    With that being said, I do know folks who spend hours a day on their cell phones. For those folks,I would guess that a BT headset might expose them to less risk from RF than the handset itself, and perhaps even from a wired headset which radiates the phone's RF (don't know how common that is with today's phones).


    JKG
     
  13. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    If you're a pilot worried about wearing BT headphones 800+ hours a year, I could understand. Maybe, if this is your concern, it might be prudent to forego the technology "on the job". If you're walking around (or worse, sitting around) with earbuds or headphones on for hours a day on a regular basis, my guess is you should be worried about danger from things other than BT tech, like getting hit by a car, mugged, or heart disease.
     
  14. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

    Joined:
    Jul 31, 2007
    Messages:
    12,986
    Location:
    Catawba, NC
    Display Name:

    Display name:
    FlyingRon
    We live in an EMF sea. The wifi/bluetooth low power spread spectrum is a drop in the bucket.
     
    wilkersk likes this.
  15. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    Like the overweight guys in line at the airport McDonald's getting their BigMac and fries for their 6 hour flight at 35,000' in an aluminum tube, getting bombarded by UV and cosmic radiation, while complaining about the TSA's X-ray scanner. Its just so far down the list of things that aren't healthy for you.
     
  16. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    That would be my parents. Sounds like one to me.

    T'is true, but the distance squared rule and the specific band in use with BT plus proximity to a hole in your head, makes it a tad more troubling.

    Like someone said, for hundreds of hours a year, not great. When needed? No big deal. Time under the curve as Doc likes to say.

    There's a reason the microwave tracker for the local TV news chopper has lights and horns on it when it's going active. Way higher power and very focused... you don't want to be in the antenna path of that beastie at the ground antenna end...
     
  17. Everskyward

    Everskyward Administrator Management Council Member PoA Supporter

    Joined:
    Mar 19, 2005
    Messages:
    30,808
    Display Name:

    Display name:
    Everskyward
    Interesting. I don't think I ever encountered one of these, although I remember dental x-rays without the protective apron. I was a kid in the 1960s.
     
  18. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    It's the inverse of distance squared for efficient energy emitters, like microwave antenna wave-guides and X-ray tubes. Meaning energy relative to the point source is reduced by a factor of 4 over a given distance.

    A BT pilots headset is not an efficient point-source emitter in this respect. Passive ear buds, with only IFs and their harmonics generated at extremely low (negligible) power, even less so.
     
  19. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    "Point source" is meaningless. There's no such thing as an isotropic antenna nor the perfect pattern created by one. Yes, earbuds are low power, they're not NO power, and they're in your ear hole. Minimizing their use to less than freaking all day long, is just common sense.

    Never said anything at all about pilot headsets. The BT TX/RX isn't essentially in your ear on those, it's down in the electronics box usually.

    Talking about sticking 2.4 transmitters in your ear. Maybe don't leave it in there ten hours a day like some people are doing. That's all I'm saying.
     
  20. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

    Joined:
    Apr 1, 2007
    Messages:
    12,853
    Location:
    PUDBY
    Display Name:

    Display name:
    Richard Palm
    My second link (to dictionary.com) claims that one generation is about thirty years. :dunno:
     
  21. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

    Joined:
    Apr 1, 2007
    Messages:
    12,853
    Location:
    PUDBY
    Display Name:

    Display name:
    Richard Palm
    Over what given distance?
     
  22. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    You're right, no such thing as a "perfect" energy transfer of any sort in the real world. earbuds are much less efficient than radar transmitters. invoking inverse square law without acknowledging relative Inefficiencies seems
    A bit misleading.
     
  23. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    Relative to a fixed distance from a point of origin, energy felt at twice the distance will be only 1/4th as intense.
     
  24. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

    Joined:
    Apr 1, 2007
    Messages:
    12,853
    Location:
    PUDBY
    Display Name:

    Display name:
    Richard Palm
    Correct.
     
  25. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Perhaps. It's hard to get across common sense sometimes. The point was even with the "best science of the day" engineers and scientists have subjected people to things we probably shouldn't have. Personally, I see no really good reason with what we know today, to jam a 2.4 GHz transmitter in my ear canal for extended periods of time. Efficient antenna/radiator or none.
     
  26. Cap'n Jack

    Cap'n Jack En-Route

    Joined:
    Jun 25, 2006
    Messages:
    4,999
    Location:
    Nebraska
    Display Name:

    Display name:
    Cap'n Jack
    From a physical chemical point of view, 2.4 GHz is pretty low power. The wavelength is too long for any molecular changes, and if definitely isn't ionizing radiation. However, the frequency is within the S-band, as is the frequency for home microwave ovens, and there is the (admittedly very, very, small, especially with the very low power used) possibility of heating some skin locally. I imagine the transceiver/antenna is outside the ear.

    The RADAR pioneers during WWII dosed themselves rather thoroughly with microwaves of these wavelengths with no ill effects that I've heard about- microwave heating was discovered by accident when a researcher melted some chocolate in their pocket by mistake. The power employed was much higher than that used by any blue-tooth device we use.
     
  27. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    The author of this article does a much better job than I do at making my point:

    [​IMG]

    The Fallacies of Risk | Planet 3.0
     
  28. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Then your point wandered off of the topic at hand. It's okay, you're allowed, but either you're refuting the wisdom of not jamming a 2.4GHz transmitter in one's ear for eight or more hours a day, or you're off comparing it to other risks. They're really not the same topic. And that's fine. But thanks for clarifying.

    I believe we went straight from "point source" which was nonsensical to "you're going to die of a heart attack" which is fine, but it does show the lack of direct response to the opinion that shoving a transmitter in your ear hole for long periods of time, isn't particularly intelligent.

    We could go into the general problems suffered by those who shove things that aren't even transmitters in their ears for extended periods of time if you like. ;)
     
  29. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    Asked and answered! ....Then, for some unknown reason, it went downhill from there. ;-)
     
    denverpilot likes this.
  30. Everskyward

    Everskyward Administrator Management Council Member PoA Supporter

    Joined:
    Mar 19, 2005
    Messages:
    30,808
    Display Name:

    Display name:
    Everskyward
    There is another current thread regarding Bluetooth hearing aids. :tongue:
     
    denverpilot likes this.
  31. weirdjim

    weirdjim En-Route

    Joined:
    Jul 8, 2008
    Messages:
    3,033
    Location:
    Grass Valley, CA (KGOO)
    Display Name:

    Display name:
    weirdjim
    I thought the vehicle of choice was a Ferrari?
     
  32. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Hell if I know what lawyers like. All the ones I know have either a Bonanza or a Cirrus and one has two warbirds. Hahah.
     
  33. JGoodish

    JGoodish Cleared for Takeoff

    Joined:
    Jun 10, 2006
    Messages:
    1,160
    Display Name:

    Display name:
    JGoodish
    Or, my job could require me to be mobile most of the time and rely on my cell phone to communicate. Or, perhaps I enjoy listing to audio books or music while I sit at my desk in a cubicle and work throughout the day. The question is a valid one, and it appears that neither you nor anyone else has enough data to reach a conclusion one way or the other.


    JKG
     
  34. JGoodish

    JGoodish Cleared for Takeoff

    Joined:
    Jun 10, 2006
    Messages:
    1,160
    Display Name:

    Display name:
    JGoodish
    That is true, but that EMF sea isn't being transmitted from the side of your head unless you're using a device which does so. Hence the question.


    JKG
     
  35. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    I've always found a cord hooked to a real serious pair of either open or closed ear headphones (Sony professional studio open ear being my favorite for work type stuff since people still walk up and talk to me anyway) work well in all of those uses. They also sound a million percent better than Bluetooth.

    But I know. It's not what the cool kids do these days. Apple took the jack off their current phone. Guess which phone I won't be buying.

    In the vehicles a hard mounted microphone and audio out of the stereo works perfect for true hands free and nothing need be stuffed in my ears.

    There's just so many excellent options (including speakerphones and mobile speakers even, although I don't do those) there's just no real need to walk around looking like the Borg with a dongle in my ear.
     
  36. Cap'n Jack

    Cap'n Jack En-Route

    Joined:
    Jun 25, 2006
    Messages:
    4,999
    Location:
    Nebraska
    Display Name:

    Display name:
    Cap'n Jack
    Aside from some very slight heating, I doubt much will happen from the use of bluetooth devices.
     
  37. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

    Joined:
    Jul 31, 2007
    Messages:
    12,986
    Location:
    Catawba, NC
    Display Name:

    Display name:
    FlyingRon
    You don't seem to understand field strength. There has never been any definitive issues show with even 850 mW (traditional analog cellular) at the side of someone's head let alone the milliwatts of spread spectrum we're talking about with BT. You are in bigger fields sitting in front of your computer than you are getting from your earbuds.
     
    wilkersk likes this.
  38. wilkersk

    wilkersk Line Up and Wait

    Joined:
    May 21, 2015
    Messages:
    731
    Location:
    Puget Sound
    Display Name:

    Display name:
    KennyW
    The very nature of "knowledge" is that all knowledge is imperfect. It is only valid just until it isn't. My original statement stands.
     
  39. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    38,567
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    Fairly rare in front of an LCD, actually. CRT, sure.
     
  40. weirdjim

    weirdjim En-Route

    Joined:
    Jul 8, 2008
    Messages:
    3,033
    Location:
    Grass Valley, CA (KGOO)
    Display Name:

    Display name:
    weirdjim
    How about the GHz. clock running dang near everything on the motherboard with little tiny wire antennas running that clock around the board? Last I looked logic levels were in the volt(s) range giving field strength in the volt(s)/meter range.

    If you will look, every lappy I've seen has an FCC part 15 type acceptance label. And if you use the LAPpy as it was intended, that field strength is near a particularly sensitive part of your anatomy.

    Jim