Yes, code 173 will control that DirecTV receiver. If you click on the name HR-44 in the database, you can see it is using code 237. That should work as well.

Standard practice is to load the codes, and test them using the remote only pointed at the front of the receiver first. Once you know the codes work, then have the codes go thru the RF to the base station. This will save you a lot of troubleshooting time.
When you get to the RF part, you have to place the IR emmiter on the front of that model DirecTV receiver very carefully. It is very fickle with placement. 1/4" to one side could mean the difference between it working or not.