[GPS_Standard] 5MHz rubidium source

[Mark GM4ISM]

Hi all,
Indeed a Rubidium standard is significantly better frequency stability than 
any OCXO, but still they drift with age.
They are usually considerbly better than crystal based systems in phase 
noise too.
The use of GPS to correct for aging has become commonplace in professional 
applications. I have actually just got a quote for one such system for 
work.. you dont want to know how much!

My standard has a quoted stability in 24hours of 2 x 10E-11   but only 1 x 
10E-10 over 1 month
with very long avaraging on the GPS standard controller, and a documented 
control range of  0.16Hz. it may be possible to correct for this long term 
drift.
my understanding of the hardware limitations is somewhat stretched though, 
but with a granularity of DAC step size calculated for this of just less 
than 1 x10E-5 Hz, this means 2 x 10e-12  for a 5 Mhz source
so if I get the settings right i may be able to approach long term accuracy 
similar to the short term stability.

Not that I need it HI
But it would be nice to know that I was  'on frequency'
redards
Mark GM4ISM