Appending extra bytes after a specific byte position

You need to add 64 bytes ff to the hex, every 2048 bytes. It should be like this: The beginning of the file is the zero offset and after 2048 bytes add (starting from offset 2048) 64 bytes ff , then again 2048 (the offset will already be 4160) 64 bytes ff and so on to the end. I tried in bbe (Binary Block Editor) approximately:

bbe -b 2048:64 -e 'A \xaa' file > modified_file

but I can't set the correct syntax.