Philadelphia is in a double exclusion zone.  This means that neither Band 5 nor Band 6 are available for full-service stations. 

Band 5 is blocked for full-service due to WMDE in Dover, DE.

Band 6 is blocked for all services due to local ABC station WPVI. 

It may still be possible to place an LPFM station in the Philadelphia area in Band 5 (76.5~81.9 MHz), but due to the close distance to WMDE's noise limited service contour, LPFM stations will have to make showings of compliance with the interference rules and may need to propose directional antennas, which involve extra costs and procedures such as proof of performance and surveyor validation of installation.  In some cases, reduced power (no less than 50 watts at 30 meters above average terrain) may be possible in lieu of a directional antenna. 

LPFM potential within 15 miles of Center City

Many of these examples would require a directional antenna.