CH

• channel

  ICAO

• This is a channel-continuity-check of transmission to permit comparison of your record of channel- sequence numbers of messages received on the channel

  ICAO

CH has 2 meanings; the right one depends on context. A weather report, a NOTAM or an ATC clearance. Got a NOTAM full of contractions? Paste it into the decoder.

Source: FAA Order JO 7340.2 Contractions. Not for operational use.