--trusted-key not cooperating/what's a "long key ID"

[Clint (cpctc)]

Supposing gpg --list-keys gives me:

c:/gnupg/pubring.gpg
--------------------
pub  1024D/aaaaaaaa 2001-11-30 myname myaddr@host.com
sub  2048g/bbbbbbbb 2001-11-30

My secret keyring is empty; all I want to use this installation of gpg for
is to encrypt to the public key above.

If I do the command:

gpg --output testenc.enc --recip "myname" --encrypt testfile.txt

I get the big warning about an untrusted key.  I can overcome that by using
"--always-trust", but I want to use --trusted-key to explicitly bypass the
message only for this one key.

So I tried the command:

gpg --output testenc.enc --recip "myname" --trusted-key
"0xaaaaaaaabbbbbbbb" --encrypt testfile.txt
gpg: key BBBBBBBB: no public key for trusted key - skipped
-same warning as before-

and

gpg --output testenc.enc --recip "myname" --trusted-key
"0xbbbbbbbbaaaaaaaa" --encrypt testfile.txt
gpg: key AAAAAAAA: no public key for trusted key - skipped
-same warning as before-

So, my questions:
- what does "--trusted-key" want from me?
- what's a "long key id"?
- what am I doing wrong?

Thanks again...