# How can I determine the signal level needed into a given antenna to produce a given magnetic field at a given distance?

I have an ETS Lindgren 6511 loop antenna that lists a magnetic antenna factor of -2.5 (best I can read the graph) at our frequency of interest.

I've found lots of information on establishing a given electric field, but nothing that speaks specifically to magnetic fields.

• If you have the electric field, you can calculate the magnetic field directly from it. Refer Antenna Design by Balanis, or Electromagnetism by Griffith. Check electromagnetic waves section. – niki_t1 Mar 1 '17 at 14:45
• I don't have access to a copy at this time. I can order it, but surely there is a web page somewhere that has the formula? – user121934 Mar 1 '17 at 16:01

So approximately: $$H = { E \over 377 }$$ H and E are the moduli of the respective field vectors.