Be aware that Pennsylvania is currently running Operation Sneak Peek and I believe it is funded until the end of August 2014.
State Police Conduct "Operation Sneak PeeK" - YourErie.com - Powered by JET 24 and FOX 66 Erie PA
Basically, this is an electronic countermeasures approach. They have set up speed display signs (mostly K-band but some Ka) on the Interstates. You will go past one and it will display your speed. The posted speed is next to the electronic display.
If you don't heed the first warning, there is a second speed sign posted farther down the road. That second sign may or may not have a state trooper posted beyond it using K-band radar (the only allowable radar in PA) to tag the speeder.
It appears that the Pennsylvania State Police have become very sneaky. They're using that second speed display sign as a cover for their own radar use.
This wouldn't be the first time they've done this. They are known to tuck themselves in alongside the speed display signs posted at the entrance to road crew work areas and nail anyone over speed. (Doubled fines in work areas in PA.)
Obviously, most radar detectors will alert constantly on the first and second speed signs but can't display any form of multiple transmitter warnings. Most people won't be able to tell that there are two radar units in use ahead (state police + speed sign) rather than just one (speed sign only).
So far I've only seen K-band speed signs in use in this operation, matching the radar type the actual police are using. This eliminates the possibility of mixed mode alerts (K + Ka) on capable detectors.