Questions regarding global_conf.json file?

[Tezla_LLC]

I have a private home network I am setting up. I am using the main chirpstack github global_conf.json for US915. The value / keys seem somewhat obvious and intuitive however when I change them it seems I break my gateway from communicating with the network so with that said can someone explain the following:

1. "lorawan_public": true, …any reason why I cannot set this to false?
2. "fine_timestamp": { "enable": false, setting this to true breaks the gateway and it no longer shows up on server. (My gateway timestamp is always showing a static time with 1999 as year and I was hoping a change on this to true would fix that??)
3. Is there a file somewhere that defines all the possible values in this file and how they can be used or am I at the mercy of source code?

Thanks

[brocaar]

This is the Semtech UDP Packet forwarder configuration, this is not a ChirpStack component.

1. Changing to private (setting to false) changes the preamble. It means you need to configure all your gateways and devices to use the same preamble.
2. The fine-timestamp needs to be supported by your concentrator shield (and requires a compatible GNSS module)
3. GitHub - Lora-net/sx1302_hal: SX1302/SX1303 Hardware Abstraction Layer and Tools (packet forwarder...) is probably the best place.

[Tezla_LLC]

Thanks @brocaar for the answers