Jee Labs Talk

This forum has moved to forum.jeelabs.net - this read-only archive is for reference only!

1. suby
   

   Hi all!

   I'm interested in your RF12-based devices for some projects, which may need need to access either to 434 MHz devices or 868 MHz devices (obviously not at the same time!). According to the IC datasheet, it seems that it is possible to make it operate at these frequencies only changing a parameter, isn't it?

   Must I consider something else? Maybe use different antennas?

   My idea is to use it as a gateway between a Modbus wired network and a remote console. I don't want to have one PCBs for each frequency.

   Thanks in advance!

   SUBY

   Posted 19/05/2010 21:06:23

2. jcw
   

   The RFM12B modules are produced for a specific frequency band. You can indeed use them for 433/868/915, but apart from needing a different antenna for best performance, I suspect that the on board RF circuit is also specifically tuned for one band.

   In a nutshell: it works, but at severely reduced range. I can control a KAKU 433 unit with 868 MHz RFM12B's, at least a few meters away. Haven't tested range, but I do get the impression that trying to communicate at 433 using two 868 MHz units is limited to perhaps one or two meters.

   Posted 19/05/2010 21:27:51

3. suby
   

   I just mean something a bit different: - there is a remote console that will operate only at 433 or 868 MHz (this is fixed!); - my box would use the same RF circuit with the appropiate antenna and would be tunned to operate at the same frequency as the remote console.

   According to your experience, it seems possible but the RF circuit performance should be better if I use the right one, isn't it?

   Ok. Maybe, instead of 100 m, the RF circuit would be 10 m, isn't it?

   Posted 22/05/2010 15:56:41

4. jcw
   

   Or 3 m. You'll have to test to find out. I don't know right now, and I suspect it also depends a lot on local factors.

   Posted 22/05/2010 16:35:23