SI4432 lowest sensitivity and data rate

Hi,

I have 2 working devices that use SI4432 @ 2KBPS with GFSK to send a couple of bytes every minute. In an effort to increase range I want to reduce data rate further, doing so gives better receiver sensitivity and hence better range.

I am using RF22 (on arduino) that provides the lowest data rate of 2KBPS. However the lowest data rate is 0.123 KBPS. How do I reduce dta rate to 0.123 KBPS with RF22?

Also the datasheet mentions receiver sensitivity as -121dBm, how much of sensitivity can be expected at 0.123KBPS?

Thanks and Regards, WonderfulIOT

Theres nothing in the specs that indicates that going lower than 2Kbps will increase the sensitivity. If you need better sensitivity, you need a better type of radio.

wonderfuliot: I want to reduce data rate further, doing so gives better receiver sensitivity and hence better range.

You wont improve the actual sensitivty of the Si4432 below a data rate of 1000bps and I spent months trying to do so for a project.

The actual sensitivity of the Si4432 is circa -95dB to -100dB, the data sheet quoted sensitivity will not be achieved in the real world where the receiver will be seeing around -105dB of noise.

Using a LoRa device at circa 1000bps it will cover up to 10times the distance of the Si4432 and as a bonus if you lower the LoRa data rate to circa 100bps, it will go 3 times further again.

mauried: Theres nothing in the specs that indicates that going lower than 2Kbps will increase the sensitivity. If you need better sensitivity, you need a better type of radio.

There is a relation between receiver sensitivity and data rate. Other things being equal, the lower the on air data rate, the better the sensitivity. This is irrespective of the chip.

srnet: You wont improve the actual sensitivty of the Si4432 below a data rate of 1000bps and I spent months trying to do so for a project.

The actual sensitivity of the Si4432 is circa -95dB to -100dB, the data sheet quoted sensitivity will not be achieved in the real world where the receiver will be seeing around -105dB of noise.

Using a LoRa device at circa 1000bps it will cover up to 10times the distance of the Si4432 and as a bonus if you lower the LoRa data rate to circa 100bps, it will go 3 times further again.

Thanks, it helps. I was trying to avoid moving to LORA but looks like thats the way to go.

wonderfuliot: Thanks, it helps. I was trying to avoid moving to LORA but looks like thats the way to go.

You can improve the range of the Si4432 by using better antennas and a very good LNA. I have managed 1200km @ 1000bps @ 100mW with handheld equipment. This sort of setup is very expensive.

There is a 1W module that uses the Si4432 so its code compatible, but a LoRa 50mW device will be cheaper and is capable of going a lot further.

For an additional cost of maybe $1 to $2 per module for LoRa devices you will have many times the range the Si4432 can provide with a very much lower overall cost.

The Si4432 is also a pain to adjust for different data rates etc, LoRa devices are easy peasy.

Thanks Srnet, its LORA then.

And as a final nail in the coffin, the Si4432 has a fairly significant internal flaw.

Supply line glitches, such as caused by the transmitt being turned on, can cause an internal reset of the devices registers which then need to be re-programmed.

In some rare cases the internal processor can crash and its goes unresponsive on the SPI interface, the only way out of this is to toggle the devices reset pin or turn off the power.