[R-390] WWV Standards and other sources

[sdaitch at kuw.ibb.gov]

"he American Military has run planet wide RF communications and reportedly off planet communications with R390's, TS505s, TS352s, TEK 505s, and AN/URM25's since the 1950s."

While that might have been correct years back, interestingly enough, digital 
comms these days may require far greater frequency stability than produced by
any of the other equipment.

This might be dated a bit, but some years ago, the USAF had upgraded an in-country 
telephone network from an analog based system to a digital system, using Rockwell
MDR-8 radios and FCC-98 mux systems.  The plan was to have LORAN receviers at each
radio and MUX terminal to keep the digital system in time and reduce the jitter on 
the network.  At one terminal point, with multiple radios, there was so much RF generated by other equipment, the LORAN unit would not lock up to the signal 
properly and output a stable timebase for the terminal.  The owners of the system
brought in an older HP cesium beam standard, and that cured all the problems.

Similarly, my employer has used GPS based time references to stabilize digital networks
used for our older digital audio distribution system.  While it is possible to 
develop the digital timebase data from the incoming digital signals, with multiple 
sources, the time base jitter can be the source of bit errors.  Using an external
timebase, with far greater stability, to drive all the in-house equipment, reduced 
the bit error rate on our incoming signals and virtually eliminated the losses of
program audio due to time base slippage.

of course, YMMV,

73
Sheldon