The IFR 4000 is a navigation communications ramp test set. IFR 4000 is a self-contained, handheld unit designed for ramp testing, but can also be used in bench test applications. It performs functional testing, signal generation and calibration of Marker Beacon (MKR), VHF Omnidirectional Radio Range (VOR, Instrument Landing System (ILS) and VHF/UHF Communications (COMM) avionics systems. The IFR 4000 allows accurate measurement of VHF/UHF transmitter frequency, output power, modulation (AM and FM) and receiver sensitivity, VHF/UHF antenna and/or feeder Standing Wave Ratio (SWR). The instrument has a Swept Localizer DDM for coupled AutoPilot testing including simultaneous Localizer, Glideslope and Marker Beacon signals, as well as simulation of VOR beacon with variable bearing.