10 Oct
2017
10 Oct
'17
5:39 a.m.
In the US, the surplus equipment market occasionally
had GPS-trained
oscillators that could provide 10Mhz and 1pps clocking as well as NMEA
output. They were parts of CDMA cellphone base stations, each of which
had at least two. The one I have was made by HP. I also have one that
is a Motorola device that was used to synchronize simulcast transmitters
in repeaters.
That is the kind of box (from other manufacturers) that we use as well, attached
to a PC with 1PPS and NMEA and to the repeater with 10 MHz.
Chrony on the PC keeps the Linux clock within 10us (usually within 1-2us) which
we require for the simulcast, and 10 MHz provides the exact transmit frequency
reference.
Power... well, maybe it has an oven stabilized crystal oscillator. Or very
old digital logic that is a bit too power-hungry. Of course a lowcost uBlox/
SiRF module is easy to get going and provide 1PPS for ntpd.
The LeoNTP box is a plugin-and-forget network clock, of course not the cheapest
solution. A Raspberry Pi can be used, I have one in the IPv6 NTP pool at
2a00:f10:103:201:ba27:ebff:fefd:984
Rob