sdrwatch: 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/sdrwatch - from package: ion

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

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