Author Topic: RFM69CW Poor signal / transmission  (Read 1476 times)

overflo

  • Newbie
  • *
  • Posts: 3
  • Country: at
RFM69CW Poor signal / transmission
« on: March 10, 2016, 11:13:05 AM »
Hi,

I got some Moteinos and soldered the RFM69CW / 868 Mhz modules myself.
I chose these because of the RFM12B compatible footprint that I use in other projects.
I wrote some code based on the Node example and successfully transmitted data from one moteino to the other.

But:

1.
I have to enable #define IS_RFM69HW  so  radio.setHighPower(); is called.
But this is not a HW module. It is a CW module.
If I dont call the setHighPower() the modules don't see each other at all even not when they are 1 cm away

2. When they see each other it is only for ~ 1-2 Meter distance
If i move them further away from each other they don't see each other anymore at all.
The usual RSSI is -79 !



I checked the antenna length (82mm).
I checked the power supply to the moteino (5V over FTDI) and 3.3V at the module side from the onboard voltage regulator.
I did read a lot of forum posts on this forum and a german microcontroller.net thread, but could not find anything to solve my problem so far.


This project will be an open source game and it will be way awesome. Please take a minute to help me out if you have any idea what is going on.
Thank you in advance.

Thank you
-overflo

--
https://metalab.at/wiki/User:Overflo

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6462
  • Country: us
    • LowPowerLab
Re: RFM69CW Poor signal / transmission
« Reply #1 on: March 10, 2016, 11:21:36 AM »
Be careful with running high power on W or CW, you can destroy them if the reflected signal heats up the die and burns the amplifiers.
Not sure what else to say.

overflo

  • Newbie
  • *
  • Posts: 3
  • Country: at
Re: RFM69CW Poor signal / transmission
« Reply #2 on: March 10, 2016, 12:52:43 PM »
thanks for the hint felix.
i will replace the modules and compile myself a new binary without the high power setting.
maybe something inside the module already broke?!
i will report back if this made a difference.

overflo

  • Newbie
  • *
  • Posts: 3
  • Country: at
Re: RFM69CW Poor signal / transmission [SOLVED]
« Reply #3 on: March 11, 2016, 01:39:40 PM »
I solved the problem by replacing the RFM69CW modules.

I got those modules over a year ago and tought they are 69HW modules so i initalized them with the .setHighPower() setup.
That this would actually DESTROY them was nothing i would have considered a possible option.
Yet it happened.

After replacing the modules i have ~ -13 RSSI and can get trough 4 thick walls.
This is way cool and i will release the game in a week or so if i can find the time to finish the project and clean up the codebase.
I am sure you will like it :)
Thanks for the hint!

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6462
  • Country: us
    • LowPowerLab
Re: RFM69CW Poor signal / transmission
« Reply #4 on: March 11, 2016, 03:10:16 PM »
Interesting, thanks for the follow up.
So this is a theory with a high plausibility. When you tell the module to use another output path, which is completely mismatched, most if not all the energy (100mW for a HW) reflects back into the RF chip, since it doesn't have anywhere to go (an antenna), effectively heating up and probably damaging some components in its path. Then you try to use it properly, and obviously it's already damaged.