Massachusetts station WFCR is buying WNNZ, a 50,000-watt outlet on 640 AM, and converting it into noncommercial operation, the WFCR Foundation announced today. WFCR began programming NPR news and talk on WNNZ in 2007 under contract with Clear Channel Communications. The $600,000 purchase, to be initially financed through a four-year loan from Public Radio Capital, secures the AM outlet for WFCR’s expanding news and information service. In August, the Amherst-based pubcaster acquired another channel for news — WNNZ-FM, a 100-watt station on 91.7 MHz that was previously operated by prep-school students of the Deerfield Academy.