# Coding Rate ever different than 4/5? **URL:** \ **Category:** End Devices (Nodes)\ **Created:** [July 29, 2020, 6:40am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857 "2020-07-29T06:40:53Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![PhilippRe](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/philippre/32/35697_2.png) [@PhilippRe](https://www.thethingsnetwork.org/forum/u/PhilippRe)\ **Post date:** [July 29, 2020, 6:40am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/1 "2020-07-29T06:40:53Z")
Hello, I am trying to calculate the “worst case” regarding EU868 1% Duty Cycle. Meaning: How often can I send a maximum sized payload (51 Bytes) at SF12. I use the [Airtime Calculator](https://www.loratools.nl/#/airtime). One open question remains: I can select the coding rate which, of course, changes the time on air. Its quite hard to find information about the coding rate other than that 4/5 is the default for LoRaWAN. Here comes my question: Is the coding rate ever changed, e.g. if the LNS finds a signal to be weak and frequently lost? Depending on the coding rate, my results vary from 04:07 minutes to 05:55 minutes. Thanks & best regards Philipp ---
**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:** [July 29, 2020, 7:45am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/2 "2020-07-29T07:45:47Z")
It’s always 4/5; see [Payload with only 2 characters and coding rate 4/7? - #14 by arjanvanb](https://www.thethingsnetwork.org/forum/t/payload-with-only-2-characters-and-coding-rate-4-7/24813/14) And note: [SF12 is only allowed in combination with ADR](https://www.thethingsnetwork.org/forum/t/can-i-register-an-abp-device-that-has-fixed-devaddr-nwkskey-and-appskey/3831/16). > [@PhilippRe](#): > > my results vary from 04:07 minutes to 05:55 minutes Minutes?! How often are you sending? Beware that the [TTN Fair Access Policy](https://www.thethingsnetwork.org/forum/t/1300) allows for at most 30 seconds time on air per device, per 24 hours. So, an [airtime of 2,793.5 milliseconds for 64 bytes on SF12BW125](https://avbentem.github.io/airtime-calculator/ttn/eu868/51) imposes a limit of 10.7 messages per day. When transmitting all day, **on average** this needs a minimum of 134.1 minutes between the starts of two uplinks, or a maximum of 0.4 messages per hour. ---
**Author:** ![PhilippRe](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/philippre/32/35697_2.png) [@PhilippRe](https://www.thethingsnetwork.org/forum/u/PhilippRe)\ **Post date:** [July 29, 2020, 8:12am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/3 "2020-07-29T08:12:41Z")
Hi, thanks for your answer! Regarding my results: I was only stating what the Airtime calculator outputs, I didnt break that down to the TTN Fair Access Policy. Best Regards Philipp ---
**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:** [July 29, 2020, 8:16am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/4 "2020-07-29T08:16:11Z")
> [@PhilippRe](#): > > I use the [Airtime Calculator](https://www.loratools.nl/#/airtime) Beware that this calculator does not automatically include the minimum of 13 bytes of LoRaWAN overhead. The 51 bytes is the maximum _application_ payload for EU868 SF10, SF11 and SF12 on 125 kHz, _assuming_ the packet does not include any MAC commands (so: assuming the LoRaWAN overhead is 13 bytes). So, you’d need to enter 64 bytes to get proper results. A bit of self-promotion: [Airtime calculator for LoRaWAN](https://avbentem.github.io/airtime-calculator/) will give you many more details. ---
**Author:** ![PhilippRe](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/philippre/32/35697_2.png) [@PhilippRe](https://www.thethingsnetwork.org/forum/u/PhilippRe)\ **Post date:** [July 29, 2020, 8:18am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/5 "2020-07-29T08:18:46Z")
Ok, I will use your calculator now, very nice! Thanks a lot! ---
**Author:** ![bertrik](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/bertrik/32/35697_2.png) [@bertrik](https://www.thethingsnetwork.org/forum/u/bertrik)\ **Post date:** [July 29, 2020, 9:45am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/6 "2020-07-29T09:45:12Z")
A long time ago, I did an experiment where I modified the code of a RFM95 based node to send packets using error correction rate 4/8 (instead of 4/5). This did actually work, even though the LoRaWAN specification says to use 4/5. This is possible because the packet format used in LoRaWAN enables a specific LoRa header that tells the receiver what correction rate is used. This was discussed in thread: [Improve node performance by changing coding rate from 4/5 to 4/8?](https://www.thethingsnetwork.org/forum/t/improve-node-performance-by-changing-coding-rate-from-4-5-to-4-8/3460) Thomas @telkamp did a more advanced experiment, as described in the thread. The improvement was marginal. ---
**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:** [July 29, 2020, 10:09am UTC](https://www.thethingsnetwork.org/forum/t/coding-rate-ever-different-than-4-5/38857/7 "2020-07-29T10:09:22Z")
Aside, adding `cr48` and the like to, e.g, [https://avbentem.github.io/airtime-calculator/ttn/eu868/51,cr48](https://avbentem.github.io/airtime-calculator/ttn/eu868/51,cr48) will also show a dropdown for coding rate. But it will disappear when one selects the LoRaWAN 4/5.