the intensities are reported here as main beam temperatures, using a beam efficiency of 0.51. The velocity scale used for the spectra is heliocentric.

The coordinates of the PNe were obtained from a compilation of optical positions (Acker et al. 1992) and accurate radio positions measured with the VLA (Zijlstra, Pottasch, & Bignell 1989; Aaquist & Kwok 1990; Condon & Kaplan 1998). In almost all cases the coordinates are known to within $\sim 1\arcsec$, and in the least favorable cases to within a few arc seconds. The coordinates are therefore not a significant source of uncertainty for the observations. Nearly all the PNe lie at low galactic latitude ($b$), with a mean value of $|b|$ of $3\fdg 8$.

Each PN was observed centered in the array. In all cases where the envelope was detected there was no significant envelope emission in the surrounding pixels. Interstellar (IS) lines were seen along most lines of sight, and they appear as emission (if they occur in the on position) or as dips (if they occur in the off position). In some cases the lines are narrow, isolated features and there is little confusion with the PN emission. In other cases, where there are 