Total posts : 45366
Again, thank you so much. You are good!
I also noticed another posting on another forum that referenced the following FCC Public Notice (dated July 24, 1991):
This still shows the 250 uV/m at 3 meters standard, it also gives an equivalence of 0.01 microwatts as a maximum ERP (Effective radiated power), which is 10 nanowatts or “close enough for government work” to your “~11.5 nanowatt” calculation.
Where I still scratch my head is it is my understanding that the so-called certified P15 FM transmitters (like some of the ones referenced in the resources section of this website, or some of the mp3 and iPod FM transmitters generally show output powers that range from 1 to 10 milliwatts. (Admittedly, many just specify the 250 uV/m at 3 meters in their specs, but some have 1 to 10 mW and I have come across some reviews and other postings where power outputs fall in this range.) It was also my understanding that manufacturers that sold certified productis tended to be conservative in their power outputs in order to protect themselves against all potential uses.
So, what accounts for the difference between the 10 or 11.5 nanowatts that the FCC and you respectively estimate and the 1 to 10 milliwatts that manufacturers seem to use? It is just having a miniscule anltenna (like a very short whip or wire that is 12 inches or less) versus the theoretical isotopic dipole? Or are there other factors as well (including my feeble understanding)?