JS8Call is software that runs on Windows, Mac or Linux (in my case from my Raspberry Pi) which sends and receives text messages directly by radio using the JS8 mode digital format. This mode is designed specifically for very weak radio signals so it will often convey accurate intelligible information where audio phone may not be understood easily. The software operates much like Whatsapp, but works only across radio signals with no Internet at all (so useful if the Internet goes down to be able to communicate). The JS8Call software controls the radio and has numerous built-in scripts for easy sending and receiving of messages.
See the attached screenshot of what the software looks like with the text message window in yellow.