PRC-9 [r]: A variant of the AN/PRC-10 tactical radio of the U.S. Army in the Korean War, differing only in operating frequency from the AN/PRC-10 and AN/PRC-8. All were backpack vacuum tube radios with preselected frequencies, introduced in 1951 and begun to be replaced by the AN/PRC-25 in 1962. It operated between 27.0 to 38.9 MHz [e]