[GPS_Standard] a parts setback

[Dave Platt]

> A point regarding the RS232 converter, I used a Jupiter TU30-D1140,  I found
> that at times it would be nice to talk to the GPS via RS232 as well, so to
> that end I installed a DPDT miniature switch on the back of my cabinet which
> switches the data in/out lines from the Control Unit and the GPS, thus
> enabling me to look at either unit with the computer.  A more elegant
> solution is to use a double RS232 converter using an XR222 chip, and 2 com
> ports on the computer.

Agreed on all points.  I'd go so far as to suggest that you use a
TTL-to-RS-232 converter which has at least three RS-232 output
lines, so that you can connect both TX-data lines (from the GPS and
controller) and also a buffered version of the PPS signal from
the GPS (to the DCD pin on one RS-232 port).

With this arrangement, you can monitor and control the FLL system
on one port, control the GPS when necessary (e.g. to switch it
into and out of position-hold mode), and feed the GPS output
(NEMA or other sentences and the PPS signal) into time-tracking
software (e.g. directly into NTPD and the kernel's PPS detector
if available, or into GPSD using software PPD capture).

A single VE2ZAZ box can thus serve both as a highly accurate
frequency standard, and as a good-to-excellent time reference
for a home or company NTP time standard system.

I know, I'm a gearhead... but I just couldn't resist the idea of
having both a good house frequency reference, and my very own
Stratum 0 NTP server :-)