Coded Squelch Systems and a Pleasant Surprise

摘要

I was reading an online thread regarding shipboard communication. In particular, on board the cruise ship Star Legend, which is reported to use 467.525MHz and 467.750MHz, both with the continuous tone-coded squelch system (CTCSS) frequency of 114.8Hz (more on this later). I later heard that 467.525 and 467.750MHz were both simplex. In addition, that 467.525MHz was mainly active with tender-to-bridge traffic and that 467.750MHz was related more to maintenance and housekeeping. For UK registered vessels, the UK Ships Radio Licence allows the use of 457.525, 457.550, 457.575, 467.525, 467.550 and 467.575MHz (25 kHz channel spacing) together with 457.5375, 457.5625, 467.5375 and 467.5625MHz (12.5 kHz channel spacing) for simplex operation, with a transmit power of up to 2W. For duplex (repeater) use, a transmit/receive split of 10MHz is used, with the base station being on the lower frequency. For example, a shipborne base station transmit frequency of 457.525MHz would have a receive frequency of 467.525 MHz.