# LMiC + lora\_pkt\_fwd: unable to receive downlinks

**URL:** <https://www.thethingsnetwork.org/forum/t/lmic-lora-pkt-fwd-unable-to-receive-downlinks/16742>\
**Category:** Uncategorized\
**Created:** [August 10, 2018, 5:45pm UTC](https://www.thethingsnetwork.org/forum/t/lmic-lora-pkt-fwd-unable-to-receive-downlinks/16742 "2018-08-10T17:45:05Z")\
**Posts on this page:** 1\
**Showing post:** 11

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**Author:** ![arjanvanb](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/arjanvanb/32/46626_2.png) [@arjanvanb](https://www.thethingsnetwork.org/forum/u/arjanvanb)\
**Post date:** [August 16, 2018, 12:02pm UTC](https://www.thethingsnetwork.org/forum/t/lmic-lora-pkt-fwd-unable-to-receive-downlinks/16742/11 "2018-08-16T12:02:26Z")

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Nice find!

> [@szymonmagrian](#):
>
> This wrong setting was almost unnoticeable to a human during debug (1 second lasted around 1.1s) but were big enough to cause RX windows timing issues.

…but would not be a huge problem for SF12, where everything takes much, much longer anyhow, so despite starting a tad too late the LoRa chip still was able to detect the preamble it was looking for when waiting for a downlink. (It doesn’t need the full preamble; this fact is also used for some single-channel gateways that support multiple spreading factors; see [Switch bandwidth and SF of node while gateway doesn't? - #5 by arjanvanb](https://www.thethingsnetwork.org/forum/t/switch-bandwidth-and-sf-of-node-while-gateway-doesnt/15095/5))

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