[time-nuts] Re: Clock displays -- eye response

[Bob kb8tq]

Hi

Actually Have Quick (at least the airborne VHF version) was developed
in parallel with SINCGARS. For quite a while it was unclear which one
would “get there” first. 

The “time transfer” function is required for crypto synch. Without it, there 
the typical radio can not lock up to the current code set. In some cases
the synch is done on the ground from a portable Rb. In others it is done
on air from the ground or (possibly) another aircraft. 

Last I heard, ARC-164’s were still happily chugging along doing their
thing ….

Bob

> On Dec 10, 2021, at 4:36 PM, Lux, Jim <jim at luxfamily.com> wrote:
> 
> On 12/10/21 12:31 PM, Brooke Clarke via time-nuts wrote:
>> Hi Hal:
>> 
>> There has been some recent research into illusions related to sight and sound.
>> https://en.wikipedia.org/wiki/McGurk_effect - related to speech
>> and search "audio optical illusion"
>> 
>> I like a crisp "tick" for clock human synchronization.
>> 
>> I wonder why there has not been more done with military "Have Quick" for time synchronization?
>> https://en.wikipedia.org/wiki/HAVE_QUICK
> 
> HAVE QUICK was a very early hopping spread spectrum system and was long since superseded by SINCGARS and other systems in the 1980s.  I don't know that it is a "source" of time.
> 
> There was a whole set of systems for loading "time" into these frequency hopping systems, since all manner of their synchronization behavior depended on time.  And in usual DoD/NATO fashion, forward and backward compatibility was often required, so you'd have a way to sync any two random radios in a battlefield situation.  Cryptographic keying is also often time based, as are frequency nets (local interference, keeping the other guy guessing, or propagation changes)
> 
> Synchronization is the "hard part" of most spread spectrum systems both Direct Sequence (PN codes) and Frequency Hopping, and that's where most of the classified stuff is - how do you synchronize reliably, how do you prevent the synchronization from being spoofed or jammed. A naive FH approach is to have a "hailing channel" and the first person transmits there, and the other person hears it, listens to a sync pattern, and then commence hopping together. This works for point to point between two stations, but doesn't work very well when you have multiple stations, not all of which can hear each other.
> 
> GPS would have been a godsend back then (although it's not very good from an Anti Jam standpoint).
> 
> 
> Dixon, in the seminal tome "Spread Spectrum Systems" kind of makes an offhand comment that synchronization is the challenging part, and then moves on "assuming we have synchronized".
> 
> 
>> It's been a part of the PLGR and DAGR GPS receivers and I expect also for the military embedded versions for a long time.
>> https://prc68.com/I/PLGR.shtml#Time
>> https://prc68.com/I/DAGR.shtml#HQ1PPS
>> Also things like the O-1814/GRC-206 Reference Frequency Rb Oscillator make us of it.
>> https://prc68.com/I/O1814.shtml
>> 
> I don't know that they make use of it, rather, they can provide sync TO a HAVE QUICK radio.
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send an email to time-nuts-leave at lists.febo.com
> To unsubscribe, go to and follow the instructions there.