# What's SF8BW500 for (AU915)? **URL:** \ **Category:** Frequency Plan\ **Created:** [February 10, 2021, 6:09am UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068 "2021-02-10T06:09:13Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![ElectronicallyE](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/electronicallye/32/48501_2.png) [@ElectronicallyE](https://www.thethingsnetwork.org/forum/u/ElectronicallyE)\ **Post date:** [February 10, 2021, 6:09am UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/1 "2021-02-10T06:09:13Z")
Reading up on the frequency plans ([https://www.thethingsnetwork.org/docs/lorawan/frequency-plans.html](https://www.thethingsnetwork.org/docs/lorawan/frequency-plans.html)) and note that there is a 9th channel for AU915 ( 9. **917.5** - SF8BW500), hence the 8 + 1 channels. What’s it for and why do some frequency plans have it and others don’t? Thanks. ---
**Author:** ![kersing](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/kersing/32/44777_2.png) [@kersing](https://www.thethingsnetwork.org/forum/u/kersing)\ **Post date:** [February 10, 2021, 8:08am UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/2 "2021-02-10T08:08:04Z")
Perhaps you could check the [Regional Parameters](https://lora-alliance.org/wp-content/uploads/2020/11/lorawan_regional_parameters_v1.0.3reva_0.pdf#page37)? Chapter 2.6.2 specifies the channel frequencies. ---
**Author:** ![TonySmith](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/tonysmith/32/46334_2.png) [@TonySmith](https://www.thethingsnetwork.org/forum/u/TonySmith)\ **Post date:** [February 10, 2021, 12:49pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/3 "2021-02-10T12:49:22Z")
@ElectronicallyE , I think you will find this is for the 9th Lora Demodulator found in a gateway. As yet this is unused on LoraWan and as described on page 14 of the SX1301 data sheet. _“This channel is intended to serve as a high speed backhaul link to other gateways or infrastructure equipment.”_ The idea is a remote gateway with no internet connection can pass traffic to another gateway, one that does have an internet connection. As yet, this relay type solution has not been defined in the LoraWan specification but could be later this year. This is pertinent for large spread out countries like Australia, I’ve been looking at this for some time with the idea of implementing a trial. There is also a FSK demodulator which is also unused at this point in time. So the take-away message, “Don’t get too excited, its not a 9th channel for a node to use”. ---
**Author:** ![Jaysmithadelaide](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/jaysmithadelaide/32/36282_2.png) [@Jaysmithadelaide](https://www.thethingsnetwork.org/forum/u/Jaysmithadelaide)\ **Post date:** [February 13, 2021, 10:47pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/4 "2021-02-13T22:47:57Z")
> [@TonySmith](#): > > So the take-away message, “Don’t get too excited, its not a 9th channel for a node to use”. I’m super excited about the concept of a gateway to gateway back haul. Like you mention, in Australia that’s a game changer in some “outback” areas where 50 - 100 km is needed. This makes solar powered “repeaters with coverage” possible. 🙂 ---
**Author:** ![cslorabox](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cslorabox/32/35697_2.png) [@cslorabox](https://www.thethingsnetwork.org/forum/u/cslorabox)\ **Post date:** [February 13, 2021, 10:58pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/5 "2021-02-13T22:58:40Z")
> [@TonySmith](#): > > As yet this is unused on LoraWan That’s simply not true, in actual fact, SF8BW500 uplink channels are defined in the AU915 regional parameters > [@](#): > > and as described on page 14 of the SX1301 data sheet. _“This channel is intended to serve as a high speed backhaul link to other gateways or infrastructure equipment.”_ That is also a theoretic possibility, but one not in practice usable without accommodating the delay of extra hops in the network timing. Default LoRaWan receive windows do not allow for this, TTN v3’s 5 and 6 second windows might in theory, but there’s no software support for such a thing: current gateways don’t have “pass this on” logic and neither they nor the network server know how to subdivide a 5 second round trip window seen at the ultimate node into shorter gateway-to-gateway timings. > [@](#): > > So the take-away message, “Don’t get too excited, its not a 9th channel for a node to use”. On the contrary, a 9th uplink channel is **exactly** what it _presently_ is, other uses are _future_ rather than _present_ possibilities. ---
**Author:** ![TonySmith](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/tonysmith/32/46334_2.png) [@TonySmith](https://www.thethingsnetwork.org/forum/u/TonySmith)\ **Post date:** [February 13, 2021, 11:04pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/6 "2021-02-13T23:04:13Z")
Exactly, that’s why i have been looking at repeater operation off and on for a while. To support this I’ve got my outdoor waterproof gateways down to less than 1 watt consumption so its ideal for a small pole mounted solar panel. Self contained, plug the solar panel directly into the gateway. ![20191006_131831-low](https://www.thethingsnetwork.org/forum/uploads/default/original/3X/e/b/eb702faef7638000511c161b47c7ae11bf35e375.jpeg) ---
**Author:** ![TonySmith](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/tonysmith/32/46334_2.png) [@TonySmith](https://www.thethingsnetwork.org/forum/u/TonySmith)\ **Post date:** [February 13, 2021, 11:08pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/7 "2021-02-13T23:08:15Z")
> [@cslorabox](#): > > So the take-away message, “Don’t get too excited, its not a 9th channel for a node to use”. Sorry, to be more accurate “Don’t get too excited, its not a 9th channel a node can use right now” ---
**Author:** ![cslorabox](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cslorabox/32/35697_2.png) [@cslorabox](https://www.thethingsnetwork.org/forum/u/cslorabox)\ **Post date:** [February 13, 2021, 11:09pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/8 "2021-02-13T23:09:48Z")
> [@TonySmith](#): > > Sorry, to be more accurate “Don’t get too excited, its not a 9th channel a node can use right now” **UTTERLY FALSE** ’ It is _in fact_ a 9th channel a node can use _right now_. ---
**Author:** ![TonySmith](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/tonysmith/32/46334_2.png) [@TonySmith](https://www.thethingsnetwork.org/forum/u/TonySmith)\ **Post date:** [February 13, 2021, 11:10pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/9 "2021-02-13T23:10:32Z")
Only if this is consistency programmed into the majority of gateways. ---
**Author:** ![cslorabox](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cslorabox/32/35697_2.png) [@cslorabox](https://www.thethingsnetwork.org/forum/u/cslorabox)\ **Post date:** [February 13, 2021, 11:12pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/10 "2021-02-13T23:12:18Z")
It’s in the official configurations. I could easily see people not having tested it in all deployments, but then who writes a config file from scratch? But it’s part of the spec, and thus would need to be implemented in any properly configured gateway. I guess the most likely case of getting it wrong would be a gateway that uses a non-standard GUI rather than a traditional config file. ---
**Author:** ![TonySmith](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/tonysmith/32/46334_2.png) [@TonySmith](https://www.thethingsnetwork.org/forum/u/TonySmith)\ **Post date:** [February 13, 2021, 11:20pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/11 "2021-02-13T23:20:58Z")
> [@cslorabox](#): > > but then who writes a config file from scratch? Take for example the SX1302, there isn’t a config file for AU915. > **[sx1302\_hal/packet\_forwarder at master · Lora-net/sx1302\_hal](https://github.com/Lora-net/sx1302_hal/tree/master/packet_forwarder)** > > SX1302/SX1303 Hardware Abstraction Layer and Tools (packet forwarder...) - Lora-net/sx1302\_hal ---
**Author:** ![TonySmith](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/tonysmith/32/46334_2.png) [@TonySmith](https://www.thethingsnetwork.org/forum/u/TonySmith)\ **Post date:** [February 13, 2021, 11:27pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/13 "2021-02-13T23:27:10Z")
Exactly, but the file format is different and I had to write my own. Now the same occurred a number of years ago at the start of LoraWan/TTN rollout. As a result there are numerous files, all slightly different, which have become the seeds of the gateways installed around the country. ---
**Author:** ![cslorabox](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cslorabox/32/35697_2.png) [@cslorabox](https://www.thethingsnetwork.org/forum/u/cslorabox)\ **Post date:** [February 13, 2021, 11:28pm UTC](https://www.thethingsnetwork.org/forum/t/whats-sf8bw500-for-au915/44068/14 "2021-02-13T23:28:19Z")
> [@TonySmith](#): > > Exactly, but the file format is different and I had to write my own It’s really not different, apart from in Semtech’s version the json in the channels section being condensed onto a line rather than having line breaks which makes no difference to a json parser: and you could simply copy and paste. In fact I just added an SX130x\_conf block to the file I was using with the sx1301. One configuration file on the embedded computer, and a daemon tries to fire up an sx1301 forwarder, if that fails it tries the sx1302 forwarder, and if that fails too loops back and keeps going until one starts. Comparing your existing sx1301 file and an sx1302 file for a different region should make short work of it. And no need to be confused by these new _optional_ fields: > “implicit\_hdr”: false, “implicit\_payload\_length”: 17, “implicit\_crc\_en”: false, “implicit\_coderate”: 1 Because “false” is the default for implicit header, and when that is false the rest does not apply and the code does not even look at it.