Author Topic: RFM69HW setup for 868MHz  (Read 4550 times)

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
RFM69HW setup for 868MHz
« on: February 08, 2016, 06:37:33 AM »
HI,

I work with RFM69HW. I got nice results with 433Mhz modules but recently I've bought 868 modules and have a problem with communication.
It looks like this:
If I setup 433 modules to work with 433 Mhz it works good (full range ~400-500m in open air);
If I setup 433 modules to work with 868 Mhz it works good (limited range);
If I setup 866 modules to work with 433 Mhz it communicates;
If I setup 866 modules to work with 866 Mhz I don't have any connection (!);

I've tried with different power levels and +20dbm mode enabled and disabled. I use a copper wire antenna cutted for proper length (~16.5cm 433Mhz | ~8cm 866Mhz)
Another few options:
Packet mode | FSK | Gaussian shaping BT=0.5
Bitrate 9.6 kbps
Frequency deviation 5KHz
FSK Channel filter bandwidth 25kHz
SyncSize 2 bytes
All of above and more options are the same for all modules.

I've run out of ideas. Could you advise any solution please?

Best regards
Arkadiusz

executivul

  • Newbie
  • *
  • Posts: 48
  • Country: ro
Re: RFM69HW setup for 868MHz
« Reply #1 on: February 08, 2016, 07:23:36 AM »
Try using another 82mm wire from gnd pin oriented to the opposite site as the antenna(which must be 82mm for 868Mhz), just to create a dipole.
I had similar problem and seems to be solved by using a dipole or ground plan.

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
Re: RFM69HW setup for 868MHz
« Reply #2 on: February 08, 2016, 07:45:56 AM »
executivul, I've read your post about Weird antenna problem. Thanks for advise I will try add dipole GND. But would it really get the long range working (like with 433MHz >400m), it would be a surprise! :) Did you checked the range?
Also I have a ground plane about 5x4cm (PCB)> The RFM is placed on that pcb.

executivul

  • Newbie
  • *
  • Posts: 48
  • Country: ro
Re: RFM69HW setup for 868MHz
« Reply #3 on: February 08, 2016, 08:24:50 AM »
My signal is pretty good with the ground plane, -60 with radio power 0 and in a place where wifi does get almost no reception. I haven't had the change to play in the open yet.

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
Re: RFM69HW setup for 868MHz
« Reply #4 on: February 09, 2016, 02:55:55 PM »
I've made dipol. I must say that there is a little improvement but still the connection is not reliable and somehow weird. I get connection from minimum 2-3 meters but it is not steady. For a few moment it's working and then I get no connection at all (from the same position). Weird thing I noticed was that the connection worked while I moved the transmitter. Then If I stop the connection stop immediately :) I think if it could be true that there are strong interference on 868Mhz in my place...

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6403
  • Country: us
    • LowPowerLab
Re: RFM69HW setup for 868MHz
« Reply #5 on: February 09, 2016, 03:02:05 PM »
Artyum,
Did you have any of these issues with a Moteino?
Or was it just with standalone RFM69 modules?

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
Re: RFM69HW setup for 868MHz
« Reply #6 on: February 10, 2016, 03:24:05 AM »
Felix, It's about standalone modules.
Could you advise if this problem could be related to my software? Please note that I get excellent results on 433 with the same code as I try to use for 868. The only thing that changes is RegFrm.

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6403
  • Country: us
    • LowPowerLab
Re: RFM69HW setup for 868MHz
« Reply #7 on: February 10, 2016, 08:40:50 AM »
It's always hard to guess.
Looks like you are using your own settings and software, and not the RFM69 library?
My guess is your settings might be the issue, I remember when I searched for a universal set of settings I ran into such behavior until I found the settings you see in my RFM69 library. I suggest you try those and see if you still are having problems.

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
Re: RFM69HW setup for 868MHz
« Reply #8 on: February 15, 2016, 07:46:28 AM »
Felix, I'll check the defaults from RFM69::initialize and see if it help. Thank you :)

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
Re: RFM69HW setup for 868MHz
« Reply #9 on: February 16, 2016, 04:33:35 AM »
I got it working after change FSK Channel filter bandwidth from 25KHz to 125KHz and Frequency deviation 5->50KHz. I wonder how it would affect the range :)

I wonder is that true that the 915 module can work on 868Mhz with no range lost?
And also on the other hand if 868 module can work on 915MHz with no range lost?

Did you make some test on it?

john4444

  • Jr. Member
  • **
  • Posts: 71
  • Country: us
Re: RFM69HW setup for 868MHz
« Reply #10 on: February 16, 2016, 09:55:42 AM »
Quote
I wonder is that true that the 915 module can work on 868Mhz with no range lost?
And also on the other hand if 868 module can work on 915MHz with no range lost?
Did you make some test on it?

Hi Artyum
Glad you got it working.
I did some initial testing across about 150', an exterior brick wall and 3 sheetrock/stud walls.
Using Felix's default settings, I couldn't tell any difference between 915 & 868-MHz, based on the RSSI values.
There was a greater variation between tests than between 915 & 868-MHz settings.
It is my understanding that I received units tuned for 915-MHz.
Units factory tuned to 868-MHz could yield different results but I would not expect it.
John AE5HQ

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6403
  • Country: us
    • LowPowerLab
Re: RFM69HW setup for 868MHz
« Reply #11 on: February 16, 2016, 11:14:17 AM »
I did some initial testing across about 150', an exterior brick wall and 3 sheetrock/stud walls.
Using Felix's default settings, I couldn't tell any difference between 915 & 868-MHz, based on the RSSI values.
There was a greater variation between tests than between 915 & 868-MHz settings.
It is my understanding that I received units tuned for 915-MHz.
Units factory tuned to 868-MHz could yield different results but I would not expect it.

My own tests with units tuned to 868 and 915 reveal similar results, the differences are not really detectable and negligible. Hope also suggested the results are negligible. Hence I do not source 868 units, only 915.

Artyum

  • Newbie
  • *
  • Posts: 8
  • Country: pl
Re: RFM69HW setup for 868MHz
« Reply #12 on: March 05, 2016, 01:31:47 PM »
Few days ago I've made test of 868 module with 915Mhz and I got very good results ~400+/-100 mters in open air. However I'm worry to sell my products based on 868 module working with 915. I wonder if the module won't have shorter lifespan etc. I'd really would like to use it since 915 is hard to get in my country and i have 868 in abundance :)

Felix

  • Administrator
  • Hero Member
  • *****
  • Posts: 6403
  • Country: us
    • LowPowerLab
Re: RFM69HW setup for 868MHz
« Reply #13 on: March 06, 2016, 05:34:33 PM »
I think you will be ok. The only difference is in the matching network of passive components, actually there is 1 or 2 components with a slightly different value.
IMHO the life span should not be influenced.