Apple doesn't publish the VHF levels of the Macintosh Portable, or of
other systems or peripherals, which is probably why you didn't locate that
information. Ironically, the Federal Communications Commission results
ARE available to the public, and can be obtained from them.
The Macintosh Portable (as well as most other products we sell) is
designed to be used in a home or work environment, and has been tested to
comply with the limits set for an FCC Class B computing device or
equivalent in all countries it is sold in. This means that it is less
"noisy" or likely to cause interference than a Class A device, which can
legally be used only in a work environment.
Page X of the Macintosh Portable Owner's Guide lists some measures that
minimize or eliminate the Macintosh Portable's potential for
radio-frequency energy interference with other electronic devices, such as
radios and televisions.