The two effects that you need are, “distortion” and “band limiting”.
Currently Audacity does not include a dedicated “distortion” effect, but the “Leveller” effect can be used for that. Higher “Degrees of leveling” settings produce noticeable amounts of distortion - for even more distortion, the effect may be applied multiple times. http://manual.audacityteam.org/man/leveler.html
“Band limiting” is simply filtering to remove or reduce low and high frequencies, so that the range of frequencies remaining lie within a reduced range. The Equalization effect can do this. Try the “AM Radio” preset, or for a stronger effect, the “Walkie Talkie” preset. http://manual.audacityteam.org/man/equalization.html
Apply the distortion (“Limiter”) first, and then the band-limiting (“Equalization”).
(The next release of Audacity will include a dedicated “distortion” effect).