FWIW I have scanned FAA manual FC-141-1 "Receivers" which covers receiver theory plus info/schematics for RF-2, AN/URR-13, RV-5, RV-8, RUQ, RVA, RV-1, RV-3, RV-4, RV-6, RCP, RHZ, RUP, RIS, RIU, RIV, RIW http://www.navy-radio.com/manuals/faa-rcvrs-fc-141-1.pdf Nick England K4NYW www.navy-radio.com