kradio4: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/kradio4 - from package: kradio4

You may install the required package with command apt-get install {package}

Error in other languages:
kradio4: bevel nie gevind nie
kradio4: comandă negăsită
kradio4: comando não encontrado
kradio4: commande introuvable
kradio4: command not found
kradio4: käsku ei ole
kradio4: không tìm thấy lệnh
kradio4: komanda nerasta
kradio4: Kommando nicht gefunden.
kradio4: kommandot finns inte
kradio4: komut yok
kradio4: nie znaleziono polecenia
kradio4: níor aimsíodh an t-ordú
kradio4: no se encontró la orden
kradio4: no s'ha trobat l'ordre
kradio4: opdracht niet gevonden
kradio4: parancs nem található
kradio4: perintah tidak ditemukan
kradio4: príkaz nenájdený
kradio4: příkaz nenalezen
kradio4: команда не найдена
kradio4: командата не е открита
kradio4: 命令找不到
kradio4: コマンドが見つかりません