Loran phase codes, revisited

This paper investigates possible changes to the Loran phase codes, and the potential improvements that such changes could provide. (The term "phase code" refers to a multiplier of plusmn1 on the envelope of each individual Loran pulse; the sequence of signs repeats every two groups or "phase code interval.") Currently, all master signals use one specific phase code and all secondary signals use another. The phase codes now in use allow for cancellation of sky wave interference (beyond 1 msec delay, that is) and for discrimination between master and secondary stations, an important consideration for legacy Loran receiver technology. The goal in this paper is to open up the discussion of phase code selection. Two important issues considered are: 1) The codes themselves - could redesigned phase codes still provide sufficient sky wave protection, yet yield improved cross rate interference rejection? 2) The allocation of the codes - currently, all secondaries share a common phase code (master signals have a different code). Could different stations have different phase codes (e.g. implementing a form of code division multiplexing)?