# Maximize LoPy message size

**URL:** <https://www.thethingsnetwork.org/forum/t/maximize-lopy-message-size/17272>\
**Category:** Pycom\
**Created:** [August 28, 2018, 10:37pm UTC](https://www.thethingsnetwork.org/forum/t/maximize-lopy-message-size/17272 "2018-08-28T22:37:51Z")\
**Posts on this page:** 1\
**Showing post:** 2

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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 29, 2018, 4:16am UTC](https://www.thethingsnetwork.org/forum/t/maximize-lopy-message-size/17272/2 "2018-08-29T04:16:20Z")

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The maximum depends on the data rate. So I assume the data rate dropped to a rate too low to allow for the 150 bytes:

> [@Fair Use Policy explained](https://www.thethingsnetwork.org/forum/t/fair-use-policy-explained/1300/1):
>
> Like for the European 863-870MHz band, the _application_ packet size varies between 51 bytes for the slowest data rate, and 222 bytes for faster rates. Note that the LoRaWAN protocol [adds at least 13 bytes](https://www.thethingsnetwork.org/forum/t/spreadsheet-for-lora-airtime-calculation/1190/4) to the application payload. And beware:
> 
> - Some libraries, [such as LMiC](https://www.thethingsnetwork.org/forum/t/what-is-the-maximum-number-of-characters-i-can-send-with-lmic/9537), only support 51 bytes for all SF.
> - Some providers, [such as the Dutch KPN](https://zakelijkforum.kpn.com/lora-forum-16/lora-frequently-asked-questions-faq-8329), only support 51 bytes for all SF.

As for why the data rate changed: maybe the node did a new OTAA Join and only succeeded at some low rate (high SF), or maybe it used confirmed uplinks and failed to receive the confirmation, hence also lowered its data rate and tried again.

In short: change your application to not need the maximum.

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