SI4432 - green module

Using Arduino General Electronics
1

This not a question, it is more some info and a warning if you plan to use this module.

I have been using the Si4432 module for quite some time now for my remote sensors.
Used frequency is between 439 an 440 MHz.
These modules are available from Ebay, mostly on a green PCB, sometimes black, and sometimes with 9 pins instead ot the more commom 12 pin version.
There is also a blue version available - see further.

When I used a recently bought module, I had problems with the RF link: the signal was far too weak compared to before.

The attaches reference schematic does not correspond 100% but gives an idea how te signal goes.
See also AN435 from SiLabs: AN435

Si4432_schema.png
Si4432_schema.png699×369 145 KB

I have done some testing and the output power on 440MHz was 15dB lower than it should be.
On another module, output power is even 30dB too low.
The tests were done using a sweep sketch on 240 / 340 / 440 / 540 MHz.
On 240 and 340MHz, the output power looks OK.

Also the RX performance using the RSSI value, on 440MHz, is 20dB worse compared to a good module.
So the link budget is 35dB less then it should be.

My idea is that on the bad modules, there must be something wrong with the valus of the low-pass and PI filters
The components on the module are very small, as well as the values so it is alsmost impossible to measure.

See the picture how to recognize a good module.
One of the bad modules has a text HW240 printed; does thes mean hardware 240MHz?

Has anybody experienced the same?

DSC09215a.jpg
DSC09215a.jpg1920×755 276 KB

Furthermore, there is more wrong with the 'green' modules.

  • There is a 'spurious' capacitor on the SPI CLK pin, why?
  • The decoupling capacitors seem to be swapped compared to the reference schematic.
  • The harmonic termination is missing

Despite this, the left module on the picture is working properly.

I have now bought the 'blue' PCB version, and this module is 100% according to the reference schematic.

SI4432 blauw.jpg
SI4432 blauw.jpg862×857 155 KB

@mods: how do i place pictures directly in the post instead as an attachement?
right-click to copy the link adres whem modifying does not give the correct link adress:
wrong :SI4432 - green module - General Electronics - Arduino Forum
right : SI4432 - green module - General Electronics - Arduino Forum
I get the right adres when viewing my post in another tab (Opera)

DSC09215a.jpg
DSC09215a.jpg1920×755 276 KB

Si4432_schema.png
Si4432_schema.png699×369 145 KB

SI4432 blauw.jpg
SI4432 blauw.jpg862×857 155 KB

2

OK, so you figured the image posting.

Unfortunately, the linking of uploaded files is badly botched in the latest (a few years old) version of the forum software, but like many other things, such as logging you off every few days, complaints fall on deaf ears. :grinning:

3

So some (no doubt very cheap) modules that use the Si4432 are not so good, what a shocker.

I would suggest sticking to an Si4432 module of known performance and pedigree, the Hope RFM22B. You would be amazed how far you can persuade them to work at.

4

The RFM22B used the RF22B chip, not Si4432.

A 15dB drop tends to suggest the antenna matching circuitry was for a different frequency.

5

MarkT:
The RFM22B used the RF22B chip, not Si4432.

The RF chip is marked as RF22 for sure, by Si I guess who then supply it to Hope.

There is the saying about the 3 tests for a duck;

The data sheets are the same.
The pinouts are the same.
The devices are interoperable.
The performance is the same.

Its a duck.

Hope do the same for the RFM98, thats actually a SX127x supplied by Semtech.

6

Thanks to the OP for this info! Happily it now seems that the blue versions are now everywhere, including a couple on my bench. Hopefully i will be able to get them running soon...although i am a real newbie at this! But many thanks for the info!