RE: FUTABA 2.4 ghz or JR 2.4GHZ?
Sorry.... where do you get the 20mW from ??
EN300-328 v 1.7.1 Page 11.... (for the Non FHSS systems)
4.3.1.2 Limit
The equivalent isotropic radiated power (e.i.r.p.) shall be equal to or less than -10 dBW (100 mW). This limit shall
apply for any combination of power level and intended antenna assembly.
4.3.2.2 Limit
For wide band modulations other then FHSS (e.g. DSSS, OFDM, etc.), the maximum e.i.r.p. spectral density is limited
to 10 mW per MHz.
There are some different degrees of interpretation of the definitions as it is not 100% tied down. Regarding measurements, Section 5.7 (page 19) stipulates EXACTLY how the measurements are to be made and how to come up with the final figures.
On reflection, I believe you are mistaking the 20mW EIRP for possibly the PSD limit ? ( And as Spektrum uses 2 channels, you have assumed that 2 channels at 10mW/MHz would give 20mW).
Information available from various sources show that the Spektrum system does not transmit on 2 "channels" simultaneously but alternates between the 2 selected "channels".
Anyway, anything that is currently legal under 328 v 1.6 would still legally be allowed to be used.