The Pack Rats maintain several VHF+ beacons, which serve as propagation indicators and allow operators to test their receivers.  The beacons are located on top of a high rise building in Center City Philadelphia, in grid square FM29jw except as noted.

Frequency Power Level Antenna
50.080 MHz 0.3 W 3 Elem Halo
144.300 MHz TBA  In FN20BE 1 Elem Halo 
222.062 MHz 4 W Single Loop
432.290 MHz 5 W Big Wheel
903.072 5 W Little Wheel
1296.264 5 W Alford Slot
2304 MHz N/A - Stay Tuned  
3456.200 5 W 16 Slot
5760 N/A  
10368.034 0.5 W 32 Slot
W3SZ Beacon Frequency Observations
Warning: Do not use these frequencies to calibrate your pace maker.
The beacons are in an unheated/uncooled room and are subject to day to day frequency changes. Use common sense.