CRX is a Hatanaka compression for Rinex file used by many permanent networks. Y. Hatanaka of GSI wrote softwares for compress/uncompress, see https://terras.gsi.go.jp/ja/crx2rnx.html.
To use the software (example of CRX compression to uncompressed RNX format):
- open a shell (e.g. Powershell)
- go to the folder containing the executable
- type “CRX2RNX.exe input.crx”
- you get as output a RNX file that you can rename to .yyo
- for help type “CRX2RNX.exe -h”