How and where to configure the channels used by the US915 band?

Your help please.
It is known that we have 64 channels of 125 KHz and 8 channels of 500 KHz for uplink, while for downlink we have 8 of 500 KHz in the US915 band.
There is the possibility of configuring all the channels for the uplink (64, 8 or both), or how would you select it?, since the width of the channel affects the payload.
WHAT CHANNELS DOES THE LoRa SERVER CHOOSE FOR UPLINK AND DOWNLINK AND HOW MANY? PLEASE

The channel-numbers for regions which have a pre-defined list of channels is configured through:

enabled_uplink_channels:

  # Enable only a given sub-set of channels
  #
  # Use this when ony a sub-set of the by default enabled channels are being
  # used. For example when only using the first 8 channels of the US band.
  # Note: when left blank, all channels will be enabled.
  #
  # For the US band, there are 64 125kHz channels (0-63) with 8 500kHz
  # channels (65-71) with frequencies in the middle of each
  # sub-band of 125kHz channels.
  # Most US LoRa gateways recieve on only one sub-band which consists of
  # 8 125kHz channels and 1 500 kHz channel
  #
  # Example: (sub-band 1)
  # enabled_uplink_channels=[0, 1, 2, 3, 4, 5, 6, 7, 64]
  # Exmaple: (sub-band 2)
  # enabled_uplink_channels=[8, 9, 10, 11, 12, 13, 14, 15, 65]
  enabled_uplink_channels=[]

https://www.chirpstack.io/network-server/install/config/

Thank you. Please, for the downlink channels, the server randomly chooses one of the channels (72-79) or how?

There are only 8 downlink channels. The downlink channel is a function of the uplink channel (uplink channel index % 8 = downlink channel index). Please refer to the Regional Parameter specification for more information :slight_smile:

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Thank you so much Brocaar