radio: 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 CentOS possible default full paths are:

/usr/bin/radio - from package: xawtv

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/radio - from package: radio

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

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