This is true. Examples from Ottawa, we have 2 stations at 99.1 and 99.7 using the same tower, 97.9 and 98.5 within 2 blocks of each other downtown, 96.5 and 97.1 on the same tower across the river and 88.5, 89.1, 89.9, 93.9, 94.5, 94.9 all from the main broadcast tower. Note how close on the dial they all are and yet none of the stations that share a tower interfere with each other. The only problem is the 2 stations at 97.9 and 98.5, although the lowest powered, interfere with everything downtown on average to below average radios....on better quality radios, they just make other stations near the middle of the dial sound much weaker.
That's where they have it right in your area, where 2nd & 3rd adjacents are rather close, & in most cases, on the same tower. In the Chicago market, 105.9 is a class B station, transmitting off the Sears Tower, while 106.3 is on a 6kw Class license (actual power is 4.4kw directional) around 20 miles south of Downtown Chicago. Now because 106.7 signed on under the current rules, 106.3 can not locate further north to reduce the interference on 105.9. That is why 106.3 has a null to the north, to protect 106.7. For 106.7, that's the same reason their frequency can not locate in Downtown Chicago, while still providing a Grade A contour over Des Plaines (106.7's COL), because of 106.3. Chicago has a number of pre-1964 short-spaced stations in the market, & that's why some stations can not locate closer to downtown. In Downtown Chicago, almost all stations are spaced .8mhz apart. I will only focus on the commercial band, since 91.5 is the only station licensed to Chicago, that transmits out of Downtown Chicago on the John Hancock (90.1 is licensed to Chicago, but operating on a grandfathered Class B license at 100kw from Addison, IL).
These are the frequencies that transmit from the Sears Tower: 93.9, 94.7, 96.3, 98.7,
100.7 101.9, 103.5, 105.9, & 107.5.
From the John Hancock, these are the stations that transmit from this building: 93.1, 95.5, 97.9, 99.5, 100.3, 101.1, 102.7, 105.1
Lastly, this is what transmits from the AON Center, 97.1 &
97.5.
Any frequency in
bold are translators, & not many on these 3 buildings at the moment.