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.

ad: L-HROutlet
ad: l-rl
ad: l-BCInc
ad: abrind-2
ad: Left-3
ad: Subscribe
ad: L-MFJ
ad: Left-2
  1. N1FM

    N1FM Premium Subscriber 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

    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 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 Ham Member 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.

  4. KK9W

    KK9W Ham Member QRZ Page

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

    W1YW Ham Member QRZ Page


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

    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.
    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
    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.


Share This Page

ad: M2Ant-1