The CARMA telescope is a heterogeneous array of 10.4, 6.1 and 3.5 m antennas,
with antenna configurations providing spacings from ~3.5 m to 2 km. This
heterogeneous array is well suited to imaging a wide range of spatial scales.
In compact configurations the heterogeneous array provides high quality short
spacing data for aperture synthesis. In extended configurations, the antennas can
be paired, with 6.1 and 10.4m antennas making science observations in the 3 mm
and 1 mm bands, while 3.5 m antennas are simultaneously observing calibration
sources within a few degrees in the 1 cm band. This unique Paired Antenna
Calibration System allows us to to correct for atmospheric phase fluctuations
and make images at 0.15 arcec resolution in a wide range of atmospheric seeing
conditions. In this paper we discuss some results and lessons learned using these
heterogeneous observing techniques. These results are relevant to all aperture synthesis
arrays, including millimeter/submillimeter wavelength arrays like ALMA,
and cm/m wavelength arrays like ATA and SKA.