In article , Kristoff Bonne writes:

Kristoff My guess, the problem is that any time-system needs some way to
Kristoff determine the time-delay between the transmittor and the
Kristoff receiver. Over a bidirectional IP-network the NTP protocol does
Kristoff work very well, but over a broadcasting-network -which is
Kristoff unidirectional by nature- it's a different story.

ntp has a "broadcastdelay" parameter for this very case. It won't help you
figure out the delay, but it will compensate by its value.

H