Confused over downlink DR

TTN Network and Services v2 Backend
1

Hello everyone. I was under the impression that TTN uses receive window 2 with SF of 9. However I am receiving SF10 in the first receive window as shown below.
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I am using a sx1276 (RF95) with a transmit power of 20 dBm and SF10BW125 for uplinks. I am located in Canada (so under US915). I am using only 902.3 MHz for uplinks. Downlinks are at 923.3 MHz.

Please help me understand the relationship of the downlink DR to the uplink DR and why TTN is using first receive window with this odd DR.

Much appreciate! Gracias
Jacky

2

Nothing odd about it at all. In RX1 the downlink spreading factor matches the uplink one, though the downlink is 500 KHz bandwidth while due to hardware limitations the uplinks are typically 125 KHZ bandwidth and so a quarter of the speed for the same SF. SF10 uplink -> SF10 downlink.

It’s RX2 that is fixed SF.

3

My understanding was that the TTN should only use RX2. I didn’t expect it to send downlinks for the RX1 window.

Is there a way to have a say in which receive windows the downlink will be in?

4

That is in EU868. RX2 in US915 is SF12BW500 on 923.3 MHz.

The network decides on the best downlink path. It may choose any of the gateways that received uplinks from your end device, and it may choose RX1 or RX2. You can’t configure that.

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6

Thanks =3