Karl Jansky and Grote Reber started the field of radio astronomy. One by serendepity and one by a deliberate decision. Following World War II English, Canadian and Australian physicists and engineers who were demobbed started radio astronomical research. From an astronomical perspective the importance of studying the heavens at radio wavelengths was recognized early on by Jan Oort in the Netherlands, Jessie Greenstein at Caltech and Harold Weaver at Berkeley. Jessie persuaded Caltech authorities to start a major program in radio astronomy (first at Palomar and then at OVRO when the importance of interferometry became clear). John Bolton was invited from Australia and he founded the Owens Valley Radio Observatory which trained a large fraction of early US radio astronomers: Clark, Kellerman, Radhakrishnan, R. Wilson (who went on to win a Nobel Prize), Rogstad, Ed Fomalont and Al Moffet. Greenstein's achievements go well beyond making Caltech a power house not only in radio astronomy but in astronomy. We are after all the best astronomy department in the world. Once a year we remember Jessie by inviting a great leader, a visionary in astronomy to come and spend some time with us and remind us of Jessie. In my view there are six giants who define modern radio astronomy and today we will be recognizing Sandy Weinreb who is one of these giants. After having delieberated for quite some time, I recall it it was about a minute or so, we chose Sandy Weinreb as this year's Greenstein Lecturer. Sandy Weinreb obtained his PhD in 1963 from the Research Laboratory for Electronics, MIT and the topic was "A Digital Spectral Analysis Technique and its application to Radio Astronomy". This was the world's first digital autocorrelation spectrometer. With this he searched for the hyperfine structure of Deuterium (327 MHz) and placed strong upper limits. Following his PhD the spectrometer was used by Sandy, Alan Barrett, Lit Meeks and J. C. Henry in the successful detection of interstellar OH, the first radio observation of an interstellar molecule. This was undertaken at the Millstone Hill 84-foot telescope of MIT's Lincoln Laboratory. Digital correlators now form the backbone of radio astronomy. Sandy then joined the nascent NRAO and rose to become the head of Electronics Division & Assistant Director. During his 23 years at NRAO he pioneered the use of low noise cooled amplifiers. He was the architect for the electronics systems of the Very Large Array. He then had a stint in industry: Lockheed Martin Laboratories and then returned to where he should have been in the first place -- Caltech. Somewhere in between Sandy developed MMIC (Monolithic Microwave Integrated Circuit) amplifiers -- another cornerstone of modern astronomy. Sandy is still young at heart and has more drive then most of us. He is a major driver for the SKA in US and at the samer time he is advising students in wide band amplifiers, investigation of Fast Radio Bursts and partnering with Greg Hallinan in the LWA. ======================================================================== John Bolton, Martin Ryle, Robert Dicke, Alan Barrett, Sandy Weinreb, Barry Clark and arguably Charlie Townes. Oort, Weaver & Greenstein ========================================================================