Gilen Tell

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9 years ago.

SX1276 Poor performance at 433 MHz band

Hi,

We have a problem with SX1276MB1MAS and ST32F411RE Nucleo boards. The PingPong tests at 433 MHz band are very poor in range, compared to 868 MHz

With a spectrum analyzer we can detect a well formed FSK spectrum signal with power levels of -70 dBm near the receiver board. But the demodulator receives the frames with errors. The theoretical sensitivity is about -105 dBm. The band is a bit more noisy in 433MHz, but this not explain this diference in range compared to 868 MHz.

We have corrected some issues in SX1276PingPong mbed application. One of those is that in callback function "OnTxDone" from DIO0 isr, it needs a delay of 2 mseconds before sending the transceiver to sleep. If this wait is not implemented, the transmitter could be sleeping when is yet transmitting the CRC bytes and the receiver could detect a CRC error. This bug seems that is only affecting to 433MHz.

However, even with the improvements, behavior at 433 MHz remains worse than expected.

Is there any error in SX1276 transceiver at 433MHz that is not documented in the errata-sheet? Has anyone experimented this behaviour in 433MHz?

Regards,

Gilen

Question relating to:

Last updated: 16 Oct 2018
SX1276 Ping Pong Demo Application Lora, Semtech, SX1276, SX1276Lib, SX1276MB1xAS

Hi. I also have a problem with 433 MHz using my SX1276MB1MAS. The maximum node-to-node communication range that I can reach for 868, 915 and 433 MHz are 500 m, 500 m, and 20 m respectively. I see that the part of the library of sx1272 for 433 MHz includes just four following channels: case CH_00_433: case CH_01_433: case CH_02_433: case CH_03_433: It looks like that the library doesn't cover all options for 433 that might be the reason for the short-range issue. Is there anyone who has the improved library to use 433 MHz by the SX1276? Any help is really appreciated

posted by Mehrdad Babazadeh 05 Feb 2018

2 Answers

Mehrdad Babazadeh
6 years, 9 months ago.

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Loren Geilen
9 years ago.

Hi Gilen,

The SX1276 shield 433MHz output has been checked as well as the code. We are unable to reproduce the issue listed. A few items could be verified to get more information. These items are: 1. Measure the output level directly at the antenna? Is the antenna on the LF side? Are you using a 433MHz antenna? Does the issue occur on another type of Nucelo board? Have you tried a second SX1276 shield to remove the possibility of a board problem?

Thx, Loren

Hi Loren,

I had posted this question five months ago. We've had suspended the project during this time and now we return. We measured the output level directly at the antenna and its OK, 10dBm? The antenna is on the LF side. We are using the 433MHz antenna that comes with SX1276MB1MAS. We bought another SX1276MB1MAS board to discard a hardware problem, but the behaviour was the same.

We had only tried it with ST32F411RE Nucleo boards. Could you say us with which Nucleo board you tried to reproduce the issue? Could you say us if you tested with the SX1276MB1MAS or the american one SX1276MB1LAS?

Could you do the test with the same Nucleo Board as us, the ST32F411RE? We have two Nucleo-F401RE too, but the design is so similar that we suspect that the behaviour will be the same.

Have there been more people who have had these same problems during this time?

In February we contacted with Semtech support but we haven't got any response about this issue.

Any suggestion?

Thank you and regards,

Gilen

posted by Gilen Tell 05 Apr 2016