Hi Jim:
Interesting paper on flashing temporal response.
"Have Quick" is primarily a spread spectrum radio protocol but it also
includes a time transfer/setting protocol.
The early Trimpack GPS receivers included a time setting output.
https://prc68.com/I/Trimpack.shtml
The PLGR & DAGR output the HQ digital data used to set the time in the O-1814 Rb. The O-1814 was part of the Program
Pacer Speak System so that inbound bombers coming from far away would hear the HQ radio transmissions.
https://prc68.com/I/MT6250.shtml
There are different flavors of HQ time protocol, but the newer one just adds data after the older one so is backward
compatible.
It's tricky to see the data. I needed to use an SRS DG535 to delay the scope trigger so that I could use a very fast
sweep speed.
https://prc68.com/I/DAGR.shtml#HQ1PPS - scroll down a little to see the HQ
setup.
--
Have Fun,
Brooke Clarke, N6GCE
https://www.PRC68.com
axioms:
1. The extent to which you can fix or improve something will be limited by how
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
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HAVE QUICK was a very early hopping spread spectrum system and was long since superseded by SINCGARS and other systems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.
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