You can try these, these are the EWR sectors within N90:
North Arrival 120.15
METRO 132.8
22 Final 125.62
Departure 119.2
Robbinsville 128.55
MUGZY 127.6
Freq Location
-----------------------
120.15 Newark (primary and backup transmitter)
132.8 Solberg
125.62 Sparta
119.2 Newark (primary and backup transmitter)
128.55 Newark (primary and backup transmitter)
127.6 Newark (primary and backup transmitter)
120.85 Solberg
These frequencies are all listed as Newark...I believe the transmitters are right next to the NJ Turnpike on the east side of the field...except the Tower, which may transmit from the antenna(s) on the Tower:
118.3, 118.85, 119.2, 120.15, 120.85, 121.125, 121.5, 121.8, 123.85, 124.75, 124.85, 125.50, 125.85, 126.15, 126.275, 126.7, 127.3, 127.6, 127.85, 128.55, 128.8, 132.45, 132.7, 134.05, 134.825, 135.575.
These are listed as Sparta: 128.25, 121.725, 118.375, 122.5, 125.625, 127.975, 133.15
These are listed as Solberg: 120.85, 132.80
These are listed as Teterboro: 119.5, 120.675, 121.50, 121.90, 122.65, 125.1, 128.05, 132.025, 122.0, 122.20
Typically they are on platforms that are not very high (maybe 10-25' high). You don't want the ground transmitters very high for air-to-ground communications in a crowded frequency band like 118-136 MHz. This is mainly to avoid or reduce co-frequency and adjacent frequency interference.
-dave