A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2018 Sep 25, 02:00 -0400
Hi. I was sent here from cruisersforum.com because I asked too many questions. By way of introduction: I have a sailboat. I write software for a living but don't know much about math or anything else, at least not compared to the people around me. I have two 19th century wall clocks in my house that are presently keeping time within a few minutes a week. 44 north, 93 west; my boat's on the Mississippi at present. I used to fly IFR and consider myself a past master of the off-airport NDB approach. I realize that I probably sound like an internet kook left over from y2k.
It is my view that HF (shortwave) services are moribund. We have recently seen the failure of shipcom (www.shipcom.com), the gradual scaling back of broadcast shortwave news services, and now the proposal to shutter WWV and WWVH. Even if the time standards survive the current round of belt-tightening, it is, how shall we say, only a matter of time before they are shut down. Because, if you believe that the GPS constellation (and GLONASS and Galileo) is immortal, it's better in every possible way than WWV. And lots of people like to believe that the GPS constellation is immortal.
Anyway, I've been accumulating a list of high-acccuracy timekeeping devices that are small and portable and inexpensive enough to be practical for a sailboat. Candidates to date include:
1) NTP100-OSC-HS from masterclock.com, at $1525. Compact, oven-controlled reference oscillator, NTP source, local display, 12 or 24v dc. Claimed accuracy +/-4 seconds a year. Falls back to a simple quartz RT clock with a lithium battery whenever power is lost.
2) Various wall clocks from brgprecision.com that appear to be marketed primarily to public safety, hospital, and emergency response users. About $300 in stock configuration, claimed accuracy to 1 second per 20 years with optional oven controlled quartz oscillator (pricing unknown), higher accuracy oscillators available including rubidium timebases, larger form factor. Correspondence with the company leads me to believe that these run on 12 vdc; a 120v wall wart with 12 vdc out is customarily provided. Confusingly broad product line, see http://brgprecision.corecommerce.com/cart.php?m=product_detail&p=319 for an example relevant to navigation.
3) HAQ (high accuracy quartz) watches from various mid- to high-end watch brands. These start at around $300 (new) with claimed accuracy of +/- 10 seconds per year. Reading the watch enthusiast forums leads me to conclude that the accuracy claims may be somewhat optimistic. Certina, Citizen, Seiko, and various higher-dollar brands all have offerings limited only by your sense of fashion, your budget, and your imagination.
The low Earth orbit communications satellites, particularly Iridium, may provide a reasonable backup also. They provide system time, worldwide, the main drawback being that they appear to see time as a convenience service and may not be handling it with sufficient care to be sure it is always accurate. I don't know whether a paid-up account is necessary to access system time. There have been notable incidents of loss of emergency communications capability due to misunderstandings over billing.