Hi All,
I have Steval STRK01 IOT tracker and Things outdoor gateway. Both are registrered on things network.
Could you please guide me how can I change spreading factor? Moreoever, How can I change it to private network?
If looking to go private check out the Learn section and the TTI docs
https://www.thethingsindustries.com/docs/
If I am on things network. How can I change the spreading factor of either gateway or steval strkt01 node?
For the gateway you can’t and you don’t want to as it would make the gateway non compliant.
For the node you could check the STM user manual on how to set either SF or DR (those are related as you know if you took the time to learn the LoRaWAN basics, if not go to the learn section and start learning the basics)
Mr Why here.
Mr Why wants to know Why you want to do this.
Because we don’t know what you are striving to achieve we don’t know the best way to answer you.
Would guess from previous posts that as a new researcher (student?) at Loughborough Uni OP is looking to get stable LoRa signal on specific SF to help grab using SDR?! 
But still doesnt tell us why - we never got a full answer on the ‘channel modelling’ and ‘retransmission’ aspects…
Hopefully wont be too disruptive to local network users… some of my GW’s/Nodes 20-30km north on other side of hills wont be disrupted but not sure about the other 2 or 3 deployed by people for the local Shepshed community. Atleast trust now figured that they will be EU868 (as would be discovered from “Learn”)
I am using LoRa siganl in forest environment for my Phd research. So I need to change spreading factor of the node sensor to see the difference. I am not going to use any signal out of the ISM band, so nothing to worry about it. The SDR generates less than 100mW of power which is save for other users.
Those doing PhD’s have plenty of time to learn a complex topic forwards, backwards & sideways over a couple or three years - in the commercial sector we work in months.
So perhaps best go and learn LW in depth before starting to try to do the actual research.
There is the Learn section. There is the specifications. There is a course (not completely recommended) with more info from a university .
There is setting up a PROPER gateway, a couple of off-the-shelf devices and then creating your own using LMIC or RadioLib (preferably both) to re-inforce concepts. Then get a Seeed LoRa-E5 dev board & ST Link and use the STM32Cube LW package so you are familiar with LoRaMAC-node.
Then you will know enough to start your obliteration of the shared ISM band research.
If you want to ask LW 101 questions here, I’ll ask the university to give us credit on your thesis.
Wow! Just …wow! 
That really gives us all confidence that you have fully read the details of the technology and the TTN implementation and more importantly really know what you are doing wrt use of precious shared spectrum (and other deployed infrastructure…every GW in range is going to allocate resources to handling your signal(s) when they hear them) … and how your ‘implementation’ will interact with and potentially impact other users… 
Having supplied nodes and GW’s to users in range of where you are I have concerns (and dont want the support calls! )
For your own sake also be aware of 
Curious what you are looking to do/characterise that likely hasnt been covered before? The technology has been around for >12 years and been in production for 11 years with lots of commercial use cases with LoRa/LoRaWAN in forestry, management, environmental protection, even fire management as well as many published academic works covering use/transmission in forested environments… Just asking as always interested in expanding knowledge base and awareness of use cases as a long term user…