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New FCC RF Safety rules come into effect on May 3 - what you need to know

Discussion in 'Amateur Radio News' started by N2RJ, Apr 27, 2021.

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  1. N1FM

    N1FM Ham Member QRZ Page

    Okay, that's what I thought! I misunderstood your first comment and thought you meant that you might be out of compliance with some degree of coax loss.

    "So (you know this, others might not) the power can be HIGHER when the actual coaxial insertion loss is measured."

    I thought you meant your output might be higher at the antenna with coax loss, but you actually meant you can use a higher output power after calculating the coax loss. Makes perfect sense now.

    Good deal; thanks.
     
    W1YW likes this.
  2. W1YW

    W1YW Ham Member QRZ Page

    SO
    Some of the 'calculators' listed actually only use the 'average power at the antenna'. Others use the 'average TX power' and let you figure out the cable loss, or put it in the calculator.

    BE CAREFUL (y'all) to see which 'kind' of power is used on the calculator you choose...

    IMO, for average 'antenna power', given duty cycle, it would be very difficult to exceed 1200+ watts at HF, on CW, for that value--without actually operating illegally on the power limit rule..to wit:

    (b) No station may transmit with a transmitter power exceeding 1.5 kW PEP.

    No mention of "average power" at the antenna in Part 97 313, at HF. A transmission 'envelope' is not the same as a 'duty cycle' average for a transmission.

    Why the confusion?

    Good question!

    One possibility is that the RF exposure is intended to deal with full exposure during transmission, and thus invokes averaging (which must include duty cycle), not 'envelope', which is the frequency-amplitude waveform-time shape of the transmission when ON..they are trying to remove 'modulation' as a factor in the calculation.

    The FCC could have made it easier by more strict , or at least defined, definitions of 'average' and 'ensure'. Perhaps they will clarify.
     
    Last edited: May 3, 2021
  3. K0VWA

    K0VWA Premium Subscriber QRZ Page

    I bet you're right. Had 4 back to back MRI's a few years ago. Felt loopy and blew chunks 10 minutes after it was over. Very tired the next day but wouldn't say I was harmed. Don't know how much power they pumped into me but I'll (hopefully) never experience that at radio frequencies.

    Advanced white matter disease. Brain thinks it's 30% older than my body. I wish I hadn't had those MRI's. Time would have been better spent on the air.

    73,
    Carl
     
  4. KK9W

    KK9W Ham Member QRZ Page

    Darn...I'm late to comply.
     
  5. W1YW

    W1YW Ham Member QRZ Page

    Carl,

    I hope you are able to get back to where you were and we all wish you the best!

    73
    Chip W1YW
     
    K0VWA likes this.
  6. DO1FER

    DO1FER Ham Member QRZ Page

    Please read the text and table in the link to Tennet in Germany (use a translator if needed). Here you are able to see what can happen in cause of to high power in the air. And its not only in cause of pacemakers. The powerlevels are in the table explained. At next these facts are from the German Department of Radiation Safety. And they are not out for a joke.
     
    W1YW likes this.
  7. K4YNZ

    K4YNZ Ham Member QRZ Page

    Never said they did. But a good RF Engineer has zero problem modeling near/far fields any frequiency. We also had HF stations. with fixed channels on HF. IF in doubt talk to a Physics ! They made the best RF Engineers I found. But this will be as hard as you make it.
    73
    Retirement is good!
     
  8. N5PTV

    N5PTV Ham Member QRZ Page

    When you open the near field tab in EZNEC...

    EZNEC+ ver. 6.0
    Blank 5/4/2021 2:51:59 PM
    ATTENTION: This software CANNOT BE USED TO tell whether (1) the
    amount of electromagnetic energy being emitted from an antenna is
    unsafe to anyone; (2) an antenna subjects anyone to potentially
    hazardous electromagnetic exposure. LICENSOR DISCLAIMS ANY AND ALL
    WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
    Other disclaimers apply. Refer to the EZNEC on-line help for
    the complete text. DO NOT USE this software to determine whether
    an antenna is emitting an unsafe or hazardous level of energy.
    --------------- NEAR-FIELD PATTERN DATA ---------------
     
    WN1MB likes this.
  9. W1YW

    W1YW Ham Member QRZ Page

    That disclaimer, as with any AND ALL NEC2 based products, is prudent. It is NOT the fault nor responsibility of the vendor. Here is what I said in POST #54:


    The recommendation of using 'EZNEC' is a poor one, IMO, in most uncontrolled environments, as objects, materials, structures, and so on, are poorly modelled within the NEC2 from an accuracy standpoint.

    It has nothing to do with 'EZ'NEC. It has everything to do with 'NEC2'--which is the usual simulator used in the version most used by hams..
     
    Last edited: May 4, 2021
  10. N5PTV

    N5PTV Ham Member QRZ Page

    What's your take on NEC4/NEC5? Commercial stuff like HFSS is very expensive. I looked at my MatlabR2019B antenna apps and there is no near field data, or I don't know where to find it.

    -Matt
     
  11. W1YW

    W1YW Ham Member QRZ Page

    I do not, overall, believe simulations are appropriate for ham compliance. IMO.

    Things like HFSS and FEKO can handle this--but by doing so they beg the question of modelling the area/environment with greater fidelity of structure. Why bother modelling TREES, BUSHES, ROCKS as part of the environment??

    Other opinions may differ, but I am very much in the camp of 'what can hams measure', with ham equipment (not limited to rigs), rather than sophisticated simulations.

    The concern of: 'do HT's meet requirements?' will likely be answered for us by manufacturers for the antenna supplied with those radios. MO.

    Still not a sniff on this voluminous thread about others' concerns with HF moderate power mobile...:-(
     
    K0UO likes this.
  12. W2QL

    W2QL Ham Member QRZ Page

    "Still not a sniff on this voluminous thread about others' concerns with HF moderate power mobile..."

    That's among the questions I have, as well. What do you consider "moderate" power? 100w CW (40%) or SSB (20%)?

    FWIW, I didn't hear as many /M during this past weekend's 4 QSO parties as I thought I would have based on other QSO parties, but maybe I wasn't paying attention.
     
  13. N5PTV

    N5PTV Ham Member QRZ Page

    I think that a model can be as granular as you want to spend time on it. Vegetation can also change effects with the seasons, water content, species, and growth. Rocks would have to be analyzed for mineral content, size, shape, and placement. That's going a bit too far for what we (the ham community) are being asked to do, I agree. I think some hand calculations are sufficient. Hams that don't work with RF professionally or are uncomfortable with the math may want to have a ham or EE to check their work (for free of course) just as a CYA. Perhaps modeling software that is typically available to hams like NEC2 can be used for a sanity check against the hand calculations. Accurate measurements are a bit more difficult to obtain with amateur equipment. Commercial equipment is way too expensive. I have used some Narda stuff at work and the cost was in the tens of thousands.

    There is a segment of the public and media that continuously spread misinformation about RF exposure, especially on social media platforms and Youtube. This is being done either out of ignorance or to profit. I saw an advertisement for an RF shielding beanie style cap on Youtube a few days ago and almost spit my coffee out. Strange times we live in for sure. The conspiracies typically include power transmission lines, smart meters, cell towers, WiFi, and now 5G. Now, I'm not going to suggest staring down an mm wavelength RADAR feedhorn but come on!

    As far as mobile operation goes, I have seen what I believe to exceed the MPE in some installations. I think moderate mobile power starts around 200 watts and does depend on mode and duty cycle. Most hams spend a great deal of time listening more than transmitting. A kilowatt in a mobile is a bit risky in my opinion, but that would depend on the antenna location. I have seen screwdriver antennae mounted on single cab pickup trucks around a foot from the drivers' or passengers' heads with just the window and headrest in between. However, this is the right of the ham to do so as long as no one else is unknowingly overexposed. I think the hobby will do fine with this additional requirement. It's not a heavy lift. Attrition, EMI/RFI (solar inverters/optimizers, EV charging, marijuana grow lights, Part 15/18 devices, etc.), licensing fees, and loss of spectrum will likely be our future challenges.

    -Matt
     
  14. G8FXC

    G8FXC XML Subscriber QRZ Page

    I would love to see a statement of what is the cheapest available device that is able to measure the fields to a sufficient level of accuracy...

    Martin (G8FXC)
     
  15. M0YRX

    M0YRX Ham Member QRZ Page

    I would love to see a ICNIRP 2020 calculator , for 10>20m we in the UK would be better off as regards seperation distances ( I THINK ?) rather than the 1998 version.
     

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