mheard: 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/mheard - from package: ax25-tools

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

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