A: According to industry forums (and avionics shops referencing the Chelton PDF), a first-time installation takes 12–16 hours from start to flight test, including drilling and calibration.
The Chelton (now part of the Cobham Aerospace Communications family) DF 935-2 is a high-precision, Low Frequency (LF) direction finder, commonly used in search and rescue (SAR) operations and helicopter emergency medical services (HEMS). Specifically, it is designed to home in on the 121.5 MHz and 243 MHz emergency beacons (ELTs). However, note the "DF 935-2" labeling can be confusing: it is more widely documented as the or the Cobham 935-2 DF antenna system.
A: Not recommended. The supplied cables are phase-matched at the factory. Standard RG-58 will have random length variations of 1–3 degrees per foot, corrupting bearing accuracy up to 15 degrees.
Remember: No matter how many YouTube videos or forum posts you watch, the DF 935-2 is a safety-of-life device. Follow the PDF exactly, use the correct phase-matched cables, and test extensively. If you cannot obtain the official PDF after a legitimate purchase, contact Cobham support directly – they will provide access.
