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I'm experimenting with low frequencies, but due to the inherent nature of LF, I strive for more transmit power and bigger antennas.

Now of course I want to comply with regulations, which allow (in my country) an average exposure of 80 V/m at this frequency.

If I'd have a T-antenna that was 15m high and 20m wide. How do I calculate/estimate at which distance I would expect this field strength? Let's say 100W PEP, and an estimated radiated power of 10 mW EIRP.

The formula that I've found applies only to the far-field, I think: https://ham.stackexchange.com/a/10078/16455

Thanks.

Mike Waters
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kernash
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Estimating the near field is best done with modeling software or empirical measurement. The details of the antenna construction and environment (the ground and any nearby conductive objects in particular) can significantly impact the near field.

That said, 100W is not much, and often regulations specify that no particular evaluation need be done if the power is below some threshold. Furthermore, low frequencies are generally safer, as sensitive parts of the body (such as the cornea) don't readily absorb the radiation. For example in the US, no evaluation is necessary below 500W PEP on the 160 meter band.

Phil Frost - W8II
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Below is a rough estimate of the near fields calculated by NEC4.2 for an elevation of 3 meters above level Earth from a transmit antenna and system as generally described in the OP, and the followup comments of the OP.

"Use with due diligence."

enter image description here

Richard Fry
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