← Test Equipment

The Toolbox — Test Equipment

IFR 4000 Nav/Comm Ramp Tester

Portable avionics ramp tester for VHF COM, VOR, ILS, marker beacon, transponder, DME, and ELT testing. Standard ground support equipment at commercial and military aviation maintenance facilities.

AviationAvionicsRamp TestingFAR 91.413
Model Note: This guide covers the IFR 4000 family. The 4000S adds ADS-B surveillance testing. The 4000SR adds DME Reply testing. Core operation and front panel layout are identical across all variants.

What It Does

The IFR 4000 is a portable ramp tester that simulates ground stations and measures aircraft avionics system performance. It can act as a VOR station, ILS localizer and glideslope, transponder interrogator, DME ground station, and COM transceiver — all from a single handheld unit connected directly to the aircraft antenna system.

It is used to perform the regulatory tests required under FAR 91.413 (transponder), as well as general maintenance verification after avionics repairs, installations, or antenna work. Most commercial operators require IFR 4000 testing after any work that could affect antenna system performance.

Front Panel Overview

Simplified front panel layout — key controls and connectors.

AEROFLEXIFR 4000 nav/comm test setCOM 121.500 MHzPWR: 12.4 W MOD: 85%RF LVL: −53.0 dBmLCD displayMODERF LVLFREQ.TONEM MODSETUPCHARGEPOWERPWRDISPLAYCTRSBKLTDDM / µALOCG / S

Simplified representation — actual layout varies slightly by firmware version.

Key Controls

ControlFunction
POWERMain power switch. Hold 2 seconds to power on/off. Backlit LED indicator confirms power state.
MODESelects test mode — COM, VOR, ILS LOC, ILS GS, MKR, XPDR, DME, ELT. Use rotary or softkeys to cycle through.
FREQ / CRSSets test frequency or VOR course. Rotary encoder with push-to-confirm. Outer ring for coarse, inner for fine adjustment.
RF LEVELAdjusts RF output level in dBm. Used to simulate weak signal conditions for receiver sensitivity testing.
MODSets modulation percentage for COM audio testing. Standard is 30% AM for VHF COM. Also selects tone frequency (1 kHz standard).
SQUELCHEnables/disables squelch on the built-in monitor receiver. Press to toggle. LED indicates squelch state.
PTTPush-to-Talk. Keys the IFR 4000 transmitter for two-way communication testing. Hold while speaking into mic.
SOFTKEYS (F1–F4)Context-sensitive function keys below the display. Labels change with each test mode. Always check labels before pressing.
DISPLAYColor LCD showing test parameters, measurements, and menus. Backlight adjustable via setup menu.
ANTENNA PORTN-type female RF connector. Connect to aircraft antenna jack via appropriate cable and adapter.
AUDIO IN/OUT3.5mm jacks for headset monitoring and audio injection. Use to verify sidetone and modulation audio quality.

Key Specifications

SpecificationValue
Frequency Range (COM)108.000 – 155.975 MHz
Frequency Resolution25 kHz / 8.33 kHz selectable
COM RF Output Power−127 to −7 dBm (adjustable)
COM Power Measurement0.1 – 100 watts
VOR Bearing Accuracy±0.5°
ILS Localizer DDM Range0 – 0.400 DDM
ILS Glideslope DDM Range0 – 0.400 DDM
Transponder ModesMode A, Mode C, Mode S (4000S/SR)
DME Channel Range1 – 126 (X and Y channels)
ELT Frequency121.5 MHz / 243.0 MHz
Power Input11 – 32V DC external or internal battery
Battery Life (typical)2–3 hours continuous operation
Operating Temperature−20°C to +55°C
WeightApproximately 5.4 kg (11.9 lbs)

Basic VHF COM Test Procedure

Overview only — full procedure with tolerances and pass/fail criteria available in the IFR 4000 course.

  1. 1.Connect IFR 4000 antenna port to aircraft VHF COM antenna jack using appropriate coax and adapter.
  2. 2.Power on IFR 4000. Allow 2-minute warm-up for frequency stability.
  3. 3.Press MODE and select COM test mode.
  4. 4.Set test frequency to match the COM radio being tested (e.g., 121.500 MHz).
  5. 5.Set RF LEVEL to −73 dBm (standard receiver sensitivity test level).
  6. 6.Set MOD to 30% AM, 1 kHz tone.
  7. 7.Verify aircraft COM radio receives the IFR signal — audio should be clear with no distortion.
  8. 8.Key aircraft COM PTT and verify IFR 4000 displays received power. Typical output is 8–16 watts for panel-mount radios.
  9. 9.Check frequency accuracy — IFR 4000 displays deviation from nominal. Should be within ±3 ppm.
  10. 10.Check modulation percentage — display should show 70–90% for a properly adjusted radio.
  11. 11.Record results in maintenance log.

Basic Transponder Test Procedure (FAR 91.413)

Overview only — full procedure with tolerances and pass/fail criteria available in the IFR 4000 course.

  1. 1.Connect IFR 4000 to aircraft transponder antenna using appropriate adapter and 1-foot coax (keep cable short to minimize loss).
  2. 2.Power on IFR 4000 and select XPDR mode.
  3. 3.Set aircraft transponder to ALT mode with squawk 1200 (or as directed).
  4. 4.Press F1 (INTERROGATE) on IFR 4000 to send Mode C interrogation.
  5. 5.Verify IFR 4000 displays correct squawk code (1200) and altitude (within ±125 feet of actual pressure altitude).
  6. 6.Check reply rate — should be ≥90% (FAA minimum). Display shows percentage.
  7. 7.Check SLS (Side Lobe Suppression) — IFR 4000 tests SLS response automatically. PASS/FAIL displayed.
  8. 8.Check receiver sensitivity — IFR 4000 reduces signal level until replies drop. Minimum sensitivity per FAA: −74 dBm.
  9. 9.Check transmitter power — minimum 125 watts peak (Mode A/C). Displayed directly on screen.
  10. 10.Document all results. FAR 91.413 requires transponder tests every 24 calendar months.

⚠️ Safety Precautions

  • •Never connect the IFR 4000 to a transmitting antenna system without confirming the aircraft radio is in receive mode first.
  • •Keep cable lengths between IFR 4000 and aircraft antenna as short as practical — long cables introduce loss that affects power measurements.
  • •Do not operate IFR 4000 near fueling operations. The unit transmits RF energy.
  • •Verify IFR 4000 calibration is current before performing regulatory tests. FAR 91.413 compliance depends on calibrated test equipment.
  • •When testing on the ramp, ensure all personnel are clear of rotating propellers and jet intakes.

Want the Full IFR 4000 Training?

The complete IFR 4000 course covers all test modes in detail — VOR, ILS localizer, glideslope, marker beacon, DME, and ELT. Includes full procedures with tolerances, pass/fail criteria, common failure modes, and an interactive front panel simulator.

View IFR 4000 Course →