Larry Kayser wrote:

Greetings All:

There is a very cheap source of very high stability reference available to
everyone.  It is the 1 PPS from almost any second hand OEM level GPS
receiver.  I have one here that cost $20 US$, about the size of what we once
[snip]

Yes,  about one year ago I was told that the Magellan OEM 5000 GPS unit
had such a 1 PPS output and bought a couple of them, only to discover
afterwards that no documentation is available on that old unit, and that
most probably no 1 second pulses are to be found on it.... :-(
If anyone reading this reflector has info on this Magellan GPS, please
help me to decide whether to throw it away, or if it can be used for the
purpose cited in the Larry's post.  Thanks

Alberto   I2PHD