[ntp:questions] Can NTP sync within 1ms

Rob nomail at example.com
Sun Apr 27 18:21:51 UTC 2014


Jochen Bern <Jochen.Bern at LINworks.de> wrote:
> [Resend to list, rather than non-working(?) sender e-mail address]
>
> On -10.01.-28163 20:59, 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.
>> 
>> The listeners should enjoy a smooth reception while driving around.
>> So of course there should be no time lag between the modulation signals
>> of the different transmitters.  Experts in the field tell us we should
>> be within 12us.
>
> I'm afraid I don't get it yet. You're trying to sync waveforms on the HF
> side (~100 MHz?) instead of switching between two transmitters on the AF
> side (couple kHz, with that much more leeway for the sync), a la
> perfectly normal car radio with RDS AF and dual tuners, because ... ?

It is not an FM broadcast system, it is an amateur radio repeater system
with wide area coverage.
Similar systems are in use, or at least have been in use, in repeater
systems used by emergency services, taxi companies, etc.

Of course it is possible to use different transmitters and find some
way to switch the receivers.  It is also possible to use a mobile phone
to communicate.

But amateur radio is about experimenting and self-education, and we just
want to see if it can be done.  In fact, it already has been done by
another group using a different system setup, and we want to see if it
can be done this way as well.



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