2.8.7.11 Subchanneling

The subchanneling feature can be used to improve the sensitivity in wide channels, and is provided for each channel in each service. During subchanneling, the physical channel is split into three subchannels where the corresponding RSSI value is determined once. The subchannel with the best receive characteristic (= highest RSSI value) is used for telegram reception. The concept is shown in the following figure.

Each subchannel uses a different frequency for RSSI sampling. Subchannel 1 is always configured with the predefined frequency f_center of the physical channel. F_center is additionally used as the base frequency for subchannels 2 and 3 but modified with a 16-bit offset value (f_offset), located in the eepServices.FREQoffset[1:0] EEPROM variable, and can be adapted in the range of 0.0 kHz to 1000.0 kHz for each service separately.


Address Service0	Name	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
0x00D1	FREQoffset[0]	FREQoffset[7:0]
0x00D2	FREQoffset[1]	FREQoffset[15:8]

Subchanneling can be activated independently for each service in the eepServices.rxSysSet.subChannelling_ENA EEPROM variable.


Address	Name	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
0x00E4	rxSysSet	subChanneling_ENA	IdScan_ENA	IFAmplifier_ENA	PathValidAfterSOT_ENA	AntennaDampingPathB_DIS	AntennaDampingPathA_DIS	switching _SDTX	switching _SDRX

Note: The bandwidth of the channel filter must ensure a 20% overlap of the subchannels. The RSSI configuration to get one RSSI sample (update period, peak/average setting) is taken from the associated EEPROM setting regardless of whether the RSSI measurement is enabled for the service or not. For more information, see RSSI Measurement.

The subchanneling requires additional time during mode start-up.