Please do not get my recommendations mixed up with other recommendations.
For reception of Philadelphia.
There is WPVI-DT VHF low band channel 6 ABC to receive so a Big All Channel antenna is required.
Above the roof install a Winegard HD7084P antenna aimed at about 230 degree magnetic compass for the the reception of the south west groups of Tv stations/channels.
Here is how to aim antennas ,
http://www.kyes.com/antenna/pointing/pointing.html.
For 1 Tv connected use no splitter.
For 2 Tv's connected use a common simple 2 way splitter.
For 3 or 4 Tv's connected use Channel Master CM3414 distribution amplifier.
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For reception of NYC there is also VHF low band channel to receive , WKOB-LD channel 2 ,
http://www.hottvchannel.com.
For reception install a second antenna system that is Exactly the same as the first antenna system.
Aim the antenna at about 40 degree magnetic compass.
The 2 antenna systems Will Not be connected together on to one coax.
The 2 antenna systems Will Be Separate all the way to the Tv/s where the 2 separate antenna systems will connect to a Remote control A/B antenna switch ,
http://www.radioshack.com , # 15-1968 , or ,
http://www.mcmelectronics.com , # 32-4425.
Using A/B antenna switches Is Channel Surfing Friendly press the button on the hand held remote control , change antennas and keep on channel surfing.
Using one antenna and a antenna rotator Is Not channel surfing friendly , must wait for antenna to rotate , and not every one in the house will agree on where the antenna is pointed.
I recommend install one antenna system first , the Philadelphia antenna system , and later install the NYC system if you choose.
Here are some Strong and Sturdy antenna mounts ,
http://www.ronard.com/909911.html ,
http://www.ronard.com/34424560.html ,
http://www.ronard.com/ychim.html ,
http://www.ronard.com.
Buy the ronard antenna mounts at solidsignal by typing the word ronard in the solidsignal search box.
Here are some places to buy antennas and etc. ,
http://www.winegarddirect.com ,
http://www.solidsignal.com ,
http://www.amazon.com ,
http://www.channelmasterstore.com.