The NCAR ELDORA and other airborne Doppler radars exhibit artifacts when strong multi-trip ground clutter overlays a weaker first trip weather echo. By phase coding the pulses, this clutter interference can be suppressed by 10s of dB thereby allowing the weather echo to be observed. Furthermore, ELDORA uses 4-5 separate frequencies on its fore and aft radars to achieve accurate parameter estimates. When the beam hits the ground, or other large reflectivity gradient, range sidelobes mask weak weather echo near the ground. Phase coding the pulses at each frequency allows similar supression of these "range sidelobes". Futhermore, other multi-frequency radars, such as RapidDow that uses separate frequencies for each of several beams, can employ phase coding to reduce interference between beams. These techniques will be described and simulated examples given.