FCC Rule 15.245 Vs 15.249

Dear All,

I am planning to make a device which operates at 915Mhz frequency and trying to make it compliance to FCC rules. No frequency hopping.

I am not sure whether I should follow 15.245 or 15.247 as it seems there might be some contradictions:

In 15.245, it says the maximum field strength of fundamental is 500mV/M
while in 15.249, it says the maximum field strength of fundamental is just 50mV/M


Which rule should I follow?

Thanks in advance,

Tony

It's all in the FCC text. In a short, the 500 mV/m (about 19 dBm ERP) applies for wide band and frequency hopping transmitters.

A brief explanation under which prerequisites the higher field strength limits can be utilized is given in TI design note DN036
http://www.ti.com/lit/ml/swrr078a/swrr078a.pdf

if it is a non-cw signal, you can time average to meet the specificaitons.

I'm no so familiar with interpretation of FCC regulations, but I read from §15.35, that averaging is only applied above 1000 MHz, while regular quasi peak measurement has to be used below 1000 MHz.

I had a 915 MHz system where it applied. I will try to find the rules.