Alternatives to GPS

[Hal Murray]

ghane0 at gmail.com said:
> Hal is on that list, so I expect he will figure things out first. 

My reading is that GPS has captured the time market.

It would be good if we could work out a reasonable backup and document how to 
set it up and how good it is.  The answer probably depends upon where you are 
located.  (and time of day)

NIST changed the modulation pattern on WWVB back in 2012.  That pulled the 
rug out from under the old high end receivers.  Some/most of them were in 
trouble anyway due to the general rise of EMI.

If you are near enough to Ft Collins CO, the low cost receivers should work.  
There is/was at least one package that uses PPS technology to watch the 
carrier and decode the signal.  I think that went in to ntpd via shared 
memory rather than being an official refclock driver.  I tried it many years 
ago and never got anything that worked well enough to be interesting.

I think the German DCF77 covers most of Western Europe.  I think there are 
several low to moderate cost receivers available.  There is a similar setup 
in Japan.

LORAN is dead in the US.  I think they pulled the plug in most of Europe at 
the end of 2015.  There is some sort of trial in the US using an old LORAN 
site and frequency.  There are occasional reports of old gear springing to 
life for a day or two.  I haven't seen any serious long range plans.

WWV is a possibility.  I've never tried it.  Whether it works for you 
probably depends on your distance from Ft Collins (or Hawaii) and the quality 
of your receiver and antenna.  There is/was a driver that knew how to tell a 
specific model of short wave receiver to switch bands/frequencies so it would 
use the best of several frequencies that WWV transmits on.

There are low cost ($20?) USB radios.  (They are about the size of a large 
thumb drive.)  I think the target is over the air TV reception.  I'm pretty 
sure they cover WWV.  Most of the work is done in software.  The SDR 
(Software Defined Radio) geeks are having fun with them.  This would be an 
interesting area to explore.

CHU is a similar in Canada.

Another possibility is ACTS.  The idea is to dial in to a phone bank at NIST. 
 It measures the delay of the phone line.  If anybody has an old modem and 
low cost land line, this would be an interesting experiment.

We should probably investigate a fallback setup of using a PPS derived from a 
low cost Rubidium.

-- 
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