Voting resources, early voting, and poll worker information - VOTE. ... Adafruit is open and shipping.
0

LoRa 868 MHz vs 915 MHz
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

LoRa 868 MHz vs 915 MHz

by eescott on Thu Jul 16, 2020 11:19 am

Hi,

It looks like the 900 MHz LoRa boards Adafruit distributes are compatible for both 868 and 915 MHz. However, when I look at the RFM95x boards on large distributor websites, they all sell them as RFM95W-868S2 or RFM95W-915S2. This suggests to me that these parts can't be swapped between the two frequencies. Can anyone help me understand what part is used in the RFM95 version of the LoRa breakout? https://www.adafruit.com/product/3231

Thanks!

eescott
 
Posts: 11
Joined: Thu Nov 07, 2019 12:38 pm

Re: LoRa 868 MHz vs 915 MHz

by drassala on Sat Jul 18, 2020 5:46 am

For these modules the chips (SX1276) are actually the same and it is possible to use a 868 at 915Mhz, and the other way around, however, the antenna matching network (on the RFM95W PCB) is different and you will not get optimal signal output. The parts that differ are the inductors and capacitors used for antenna matching. These components are located between the SX1276 and the antenna. It is best that you order the RFM95W that is matched for the frequency you plan to use it on to get optimal transmission and reception. Does this help explain it a little?

The item you linked "Adafruit LoRa Radio FeatherWing - RFM95W 900 MHz - RadioFruit" is for 900Mhz (or 915Mhz). This would not be optimal for the 868Mhz band. This would be the choice if your country uses 900Mhz (or 915Mhz).

drassala
 
Posts: 13
Joined: Wed Jan 25, 2017 2:04 am

Re: LoRa 868 MHz vs 915 MHz

by eescott on Sat Jul 18, 2020 2:46 pm

Yes, that's very helpful. The piece I was missing was that the SX1276 is shared and the difference is the matching network. It seems like using the 868 MHz setup at 915 MHz and vice versa isn't ideal but would probably work for applications that aren't pushing the limits of range. Thanks!

eescott
 
Posts: 11
Joined: Thu Nov 07, 2019 12:38 pm

Please be positive and constructive with your questions and comments.