You can usually find the location of the various sites for a simulcast system by following specific links in the details of the system in question. You mentioned monitoring Philadelphia, so I'll use that system.
Go to the system in the
database.
On the systems page, look at the sites.
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Click on Zone 1 Simulcast.
That gets you here:
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Down toward the bottom of the page, you'll see the line labeled Site FCC Licenses. There is a small icon at the end of that line, next to the lower left corner of the map.
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Click on that.
That will get you to a map page showing the site locations for the simulcast.
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I highlighted your city on the map.
Since the two licenses shown are used by both Zone 1 & Zone 2, you'd see the same map if you clicked on the Zone 2 Simulcast in place of Zone 1.