2.4 GHz SPI transceiver module (nRF24L01+ class) for proprietary short-range links

01

Air data rate against sensitivity and current on an nRF24L01+ radio

Nordic's nRF24L01+ product specification shows what each data rate costs in link budget. Slower air rates buy receiver sensitivity; the transmitter's current depends on the power setting, not the rate: [1]

Transmit current is 11.3 mA at 0 dBm, 9.0 mA at −6 dBm, 7.5 mA at −12 dBm and 7.0 mA at −18 dBm, the four programmable power steps. Start-up from standby takes at most 130 µs, the SPI runs at up to 10 Mbps, payloads are 1 to 32 bytes, and a six-pipe MultiCeiver receiver supports 1:6 star networks. The chip accepts a ±60 ppm 16 MHz crystal. [1]

Editorial calculation: going from 2 Mbps to 250 kbps improves sensitivity by 12 dB (−82 to −94 dBm). In free space every 6 dB doubles range, so the slow rate gives about four times the range of the fast one at the same power, at one eighth of the raw air rate.

Ebyte's E01-2G4M01S1B, a 12 × 19 mm SMD module with PCB antenna on this radio class, lists −92 to −94 dBm sensitivity at 250 kbps, 4.5–5.5 dBm maximum output, 12.5–13.5 mA in transmit and 11.5–12.5 mA in receive, 1 µA sleep, a 2.0–3.6 V supply and −40 to +85 °C operation, with a reference distance of 200 m in open air at 2.5 m height and 250 kbps. [2]

Give the supplier the air data rate, required range and environment, antenna type (PCB, chip, U.FL/IPEX), output power, supply voltage and logic level, sleep current target, operating temperature, footprint (SMD half-hole or pin header), the markets the product will be sold in, and whether the module must carry its own FCC/CE certification.

02

The chip tunes to 2525 MHz; the licence-exempt band stops at 2483.5 MHz

The nRF24L01+ operates from 2400 to 2525 MHz in 1 MHz steps and offers 126 RF channels, and Nordic's footnote is explicit that regulatory standards determine the band range you can use. [1] Ebyte lists its E01 modules at 2.4 to 2.525 GHz. [2] [3]

FCC §15.249 and §15.247 both define the 2.4 GHz band as 2400–2483.5 MHz. [4] [5] Editorial calculation: channels 0 to 83 (2400–2483 MHz) fall inside that band; channels 84 to 125 (2484–2525 MHz) lie outside it. At 2 Mbps, with 2 MHz spacing, the channel at 2483 MHz would extend past the band edge, so firmware should keep the top channel lower; confirm the band edge with the test lab.

Editorial note: ask the module supplier which channel range its firmware examples and its certification test reports used, and lock the channel table in your own firmware.

03

5 dBm, 20 dBm or 27 dBm, and the FCC rule each one falls under

FCC §15.249 lets a transmitter in 2400–2483.5 MHz radiate a fundamental field strength of 50 mV/m measured at 3 m, with harmonics at 500 µV/m and other out-of-band emissions at least 50 dB down; above 1 GHz these are average limits and peaks may exceed them by no more than 20 dB. [4]

Editorial calculation: for a far-field, free-space emitter, EIRP = (E × d)² / 30. With E = 0.05 V/m and d = 3 m that is 0.00075 W, about −1.2 dBm EIRP. A 5 dBm module, even with a 0 dBi antenna, therefore exceeds the §15.249 average limit unless its power is set lower, and a 27 dBm (500 mW) module is about 28 dB over it.

Higher power needs §15.247, which allows digitally modulated systems up to 1 W peak conducted output if the 6 dB bandwidth is at least 500 kHz and power spectral density stays at or below 8 dBm in any 3 kHz; the 1 W assumes antenna gain of at most 6 dBi, with power reduced dB for dB above that except for fixed point-to-point links. [5] Editorial note: whether a GFSK packet radio at a given data rate meets the 500 kHz bandwidth test is a measurement, not a datasheet value; ask the supplier for the module's FCC test report and grant, and which rule it was certified under.

The PA/LNA version also changes the power budget: Ebyte lists 700 mA instantaneous transmit current for the 27 dBm module, against about 13 mA for the 5 dBm one, so the host supply and battery must handle the peak. [3] [2]

04

Send the link and the markets with the enquiry

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Link: [range; environment; data rate; payload size]
Radio: [nRF24L01+ or compatible; channel range used]
Power: [TX dBm; PA/LNA yes/no]
Antenna: [PCB / chip / U.FL-IPEX; gain]
Supply: [voltage; peak current budget; sleep current]
Package: [SMD half-hole / pin header; size]
Environment: [temperature]
Certification: [FCC rule and grant; CE; test reports]

See manufacturer records Send an enquiry through CNFX