Chelton Df 935 2 Pdf Install May 2026

Because the Chelton DF935 is an older legacy unit (often found in retrofit situations), the "installation" process is typically divided into two phases: Physical Installation and Configuration/Calibration.

Here is a feature overview and an installation guide based on standard aviation practices for this type of equipment. chelton df 935 2 pdf install

Section 6: Verification & Troubleshooting

The final section includes a 2-channel-specific checkout: Because the Chelton DF935 is an older legacy

• Apply a test signal from 45° azimuth. Verify both channels display the same bearing ±2°.
• If not, the PDF guides you through swapping RF cables to isolate a faulty channel.
• A troubleshooting table (Table 6-4) lists error codes like E-22 (Channel 2 PLL unlock) and E-35 (Inter-channel phase mismatch).

Phase A: Physical Mounting

• Panel Cutout: The manual will specify the standard aviation cutout size (typically a standard 3-inch ATI mount, but verify the exact millimeter dimensions in the PDF).
• Mounting Rails: The unit usually slides into a rack (often a standard MS2527 or Chelton-specific tray). Ensure the rack is secured to the airframe structure behind the panel.
• Cooling: While solid-state, these units still require airflow. Ensure there is space behind the unit for heat dissipation and that no wires are blocking the cooling vents.

Part 3: Anatomy of the Installation PDF – A Section-by-Section Walkthrough

Once you have the legitimate PDF, it is easy to be overwhelmed. The manual is structured for engineers, not casual readers. Below is a roadmap to the most critical sections for a 2-channel install. Apply a test signal from 45° azimuth

3.2 Special Tools Required

• Vector Network Analyzer (VNA) – For matching the four antenna elements.
• Time Domain Reflectometer (TDR) – To verify coax cable lengths (critical for phase matching).
• Digital inclinometer – For mounting the antenna array perfectly level with the aircraft longitudinal axis.
• Torque screwdriver – All RF connectors require specific torque (often 5–7 in-lbs for SMA/MCX).

1. The OEM Support Portal

The primary source is the official Chelton/Cobham customer support portal. You will likely need a registered account using your company’s EIN or ICAO code.

• Search strategy: Go directly to Cobham Aerospace Communications’ technical library.
• Keywords inside portal: Use DF-935-2, Installation Manual, P/N 957-6020-02 (typical part number for the manual).
• File name clue: The official PDF is often named IM_DF935-2_RevX.pdf.

Phase 1 – Pre-Installation (1 day)

1. Download the PDF and print the wiring diagrams (color, at least 11x17").
2. Inventory your kit: DF-935-2 unit, rack, 4 antennas, 50-pin D-sub backshell, and RF cables (RG-400 or better).
3. Verify aircraft weight & balance with the added 6.5 lbs (2.95 kg) of the DF system.

Phase 4 – Software & Calibration (1 day)

10. Load the DFconfig software and set the 2-channel mode.
11. Run the internal BITE (Built-In Test Equipment). Channel 2 should show "PASS".
12. Conduct the ground calibration with a signal generator at 4 cardinal points. Record the offset table.

5.3 Flight Test

• Perform a test flight with a known ground transmitter.
• Verify bearing accuracy of ±5 degrees (90% of the time) as per DO-220 standards.
• Record results in the aircraft logbook.