Frame acknowledgement
There is no content in the text field for these messages.
None.
These frames are used to acknowledge the receipt of a previous frame from either the aircraft or ground station. The ack field specifies the t-be-acknowledged frame's blk_id. If an acknowledgement is not received by the other party, the originator will send a duplicate after a timeout interval. The timeout interval has not yet been determined. We are not sure if there is any value to us aside from DXing.