User's Manual

9
Modulation method
This Device uses Frequency Hopping Spread Spectrum (FHSS) as its modulation technique. The list of
frequencies are as follows:
Frequency in Mhz
902.3
902.5
902.7
902.9
903.1
903.3
903.5
903.7
903.9
904.1
904.3
904.5
904.7
904.9
905.1
905.3
905.5
905.7
905.9
906.1
906.3
906.5
906.7
906.9
907.1
907.3
907.5
907.7
907.9
908.1
908.3
908.5
908.7
908.9
909.1
909.3
909.5
909.7
909.9
910.1
910.3
910.5
910.7
910.9
911.1
911.3
911.5
911.7
911.9
912.1
912.3
912.5
912.7
912.9
913.1
913.3
913.5
913.7
913.9
914.1
914.3
914.5
914.7
914.9
The FCC regulations for systems using frequency hopping spread spectrum (FHSS) techniques
can be summarized as follows:
• Frequency hopping systems shall have hopping channel carrier frequencies separated by a minimum of
25 kHz or the 20 dB bandwidth of the hopping channel, whichever is greater. The system shall hop to
channel frequencies that are selected at the system hopping rate from a pseudo randomly ordered list of
hopping frequencies. Each frequency must be used equally on the average by each transmitter (Ref:
15.247(a)(1))
• If the 20 dB bandwidth of the hopping channel is less than 250 kHz, the system shall use at least 50
hopping frequencies and the average time of occupancy on any frequency shall not be greater than
400ms within a 20 second period (= 0.4 * 50 channels). If the 20 dB bandwidth of the hopping channel
is 250 kHz or greater, the system shall use at least 25 hopping frequencies and the average time of
occupancy on any frequency shall not be greater than 400 ms within a 10 second period (= 0.4 * 25
channels). In addition the maximum allowable 20 dB bandwidth of any hopping channel is 500 kHz
(Ref: 15.247(a)(1)(i))
• The maximum peak conducted output power shall not exceed 1 W (+30 dBm) for systems employing at
least 50 hopping channels and 250 mW (+24 dBm) for systems employing less than 50 hopping
channels, but at least 25 hopping channels. As opposed to systems employing digital modulation,
averaging measurement methods are not permitted (Ref: 15.247(b)(2))