gpsk31 software package provides GTK-based psk31, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gpsk31
gpsk31 is installed in your system.
Make ensure the gpsk31 package were installed using the commands given below,
$ sudo dpkg-query -l | grep gpsk31 *
You will get with gpsk31 package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Ham Radio |
| Package | gpsk31 |
| Version | 0.5-6 |
| Description | GTK-based psk31 |
| Sub Section | hamradio |