Out-file strange format

I have written a small simple script to login to an FTP server as follows

$GenericFTPFile = 'c:\ftp.txt'
$FTPCMD = 'ftp.exe -i -s:'
$BuiltFTP = $FTPCMD+$GenericFTPFile
$FTPServer = "ftp.rsc-dev.org"
$FTPUser = "user1"
$FTPPAss = "pspsps"
$a = @()
$a += $FTPServer
$a += $FTPUser
$a += $FTPPAss
$a | out-file c:\ftp.txt

invoke-expression -command $BuiltFTP

The issue I get is that the ftp.exe -s:c:\ftp.exe can't read the file, instead I get just a weird square character and the first letter in the file displayed and FTP says it 'invalid character'

Any ideas anyone?

Thanks

Alter De Ruine