I'm not sure how Uniden approves systems into their master database, but I would take a guess that it doesn't have any talkgroups listed in it or it's not actively used yet, so it isn't showing up.
There should be a way, however, to manually insert the frequency/frequencies into a favorites list in Sentinel then push it to the scanner. I have a BCD436HP, so I'm guessing this may work for the HomePatrol series, if they both use the same Sentinel software or closely mirror them visually.
This is untested, but it may work:
1. In Sentinel, create a new favorites list and name it
2. Right click on the new favorites list, click Program Favorites List to open it in the editor
3. Create new system, name it and choose P25 trunk
4. In the left hand panel, click on the newly created system.
5. Click on "Sites" tab
6. Create a new site and name it
7. In the left hand panel, click on the newly created site
8. Enter in the frequencies under the "Frequencies" tab
9. (This may or may not be needed) Enter in the latitude, longitude, and range under "Location" tab. Ensure circle is selected and enter in the information as found in the last few rows of the simulcast table for the P25 system. (
Simulcast Site Details (Montgomery County, MD (P25)))
10. Save and push to the scanner
Once TGs go out, up to you if you want to delete this favorites list and replace it with the pre-populated one from the master database once it's up on RRDB.
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Edit: while I was typing up the instructions, your question got answered! Also, the method you chose also works! Good luck with scanning!