Came across an interesting reference to SCR-183 in the following: http://sill-www.army.mil/famag/1933/SEP_OCT_1933/SEP_OCT_1933_PAGES_450_461.pdf This discusses tests of 45-75 megacycle frequencies using an SCR-183-T4. Obviously this is *not* the equipment known and loved today as the SCR-183 family. Jack Antonio WA7DIA/4