We have selected a small sample of post-AGB stars in transition towards the planetary nebula and present new Very Large Array multi-frequency high-angular resolution radio observations of them .
The multi-frequency data are used to create and model the targets ’ radio continuum spectra , proving that these stars started their evolution as very young planetary nebulae .
In the optically thin range , the slopes are compatible with the expected spectral index ( -0.1 ) .
Two targets ( IRAS 18062+2410 and 17423-1755 ) seem to be optically thick even at high frequency , as observed in a handful of other post-AGB stars in the literature , while a third one ( IRAS 20462+3416 ) shows a possible contribution from cold dust .
In IRAS 18062+2410 , where we have three observations spanning a period of four years , we detect an increase in its flux density , similar to that observed in CRL 618 .

High-angular resolution imaging shows bipolar structures that may be due to circumstellar tori , although a different hypothesis ( i.e. , jets ) could also explain the observations .
Further observations and monitoring of these sources will enable us to test the current evolutionary models of planetary nebulae .