Does anyone know anything about Military Radio AN/URR-13 R-266/URR-13 please help.

Just google it:

http://hereford.ampr.org/millist/m20.html#a3943

AN/URR-13
Radio receiving set, UHF, 225-400 MHz, AM, 115 VAC 50-60 Hz 125 W, 9x19x18, 57 Lbs, Federal telephone, replaces RED, Major Components:

R-266/URR-13 Radio receiver,
F-89/URR-13 Band suppression filter