Preventing rsync of copying always all files to my pen

[Paul Smith]

Dear All,

I have often to synchronize a directory from my computer to a pen
drive. To accomplish this, I use the following command:

rsync -urva --delete /home/psmith/mydirectory/ /media/MYPEN/mydirectory/

However, it always requires copying all the files and not only the
modified ones. Since the directory is a large one, this is not
practical. In truth, I could use cp instead of rsync, as rsync gives
me no extra usefulness. How can I solve this problem?

Let me add that my pen is formatted with FAT, and that I need to read
the synchronized directory on MS Windows.

Thanks in advance,

Paul