[ntp:questions] Can NTP sync within 1ms

Henry Hallam henry at pericynthion.org
Sun Apr 27 17:42:54 UTC 2014


On Apr 27, 2014 10:19 AM, "David Woolley" <david at ex.djwhome.demon.invalid>
wrote:
>
> On 27/04/14 17:28, Rob wrote:
>>
>> We are setting up a co-channel diversity network.  That means multiple
>> FM transmitters that are transmitting the same signal on the same
>> frequency on different sites, where the receive areas partly overlap.
>
>
> This problem has already been solved using COFDM (aka DAB) and it is much
more tolerant of fading that is inevitable with co-channel transmitters
than your system.

DAB is a nice system but unfortunately there are parts of the world where
DAB receivers are unheard-of.

> Your transmitters will have to be contained within a circle of 3.6km,
reduced by the timing errors in the modulation at 0.3km/microsecond.

Only the distance between the receiver and all transmitters strong enough
for it to receive need be < 4 km.  The overall network can be bigger if
each transmitter is weak enough not to be heard too far away.

Of course there will still be multipath issues with destructive
interference at the carrier frequency even at much shorter distances.

Henry


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