Accuracy
Theoretically a TACAN should provide a ninefold increase in accuracy compared to a VOR but operational use has shown only an approximate 3-fold increase.
Accuracy of the 135 Hz azimuth component is ±1° or ±63 m at 3.47 km. Accuracy of the DME portion is 926 m (±0.5 nautical mile) or 3 percent of slant range distance, whichever is greater - see FAA 9840.1 1982.
TACAN stations can provide distance up to 390NM
Current Modern TACANs are much more accurate. The requirement now is to have portabe TACAN that is IFR certifiable, both Station and Portable systems. The latest modern version of TACAN have been tested to an average error of 0.00 in both range and azimuth, and could be a feasible back-up to future Air Traffic Control Systems and may even be integrated into systems for a seamless back up.
Past TACANs have relied on high power out (up to 10,000 Watts)to ensure good signal in space to overcome nulls present in antenna design and to get to their required 200 mile range. With the advancement of technology antenna design has improved with antennas with higher gain, much more shallow nulls, and lighter construction. Now it's feasible to still have the 200 nm range with a 400 Watt TACAN Receiver Trasnmitter, making the TACAN package much smaller, more portable and more reliable (Power = Heat which shortens the life of electronics).
TACAN is getting smaller: Full TACAN coverage can now be provided in a system that can be carried on a single trailer weighing less than 4000 lbs, and emplaced with two people in less than an hour. TACAN Receiver Transmitters can now be as small as lunch boxes (with full coverage and range) and the antennas can be reduced from 800 pounds to <100 pounds.
Read more about this topic: Tactical Air Navigation System
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