[time-nuts] HP5065B !!!

[EWKehren at aol.com]

I am still sitting here trying to figure out the purpose  of posting the 
article on laser diode pumping of the Rb. One look at the data  and it is 
clear that Corby’s work far surpasses the data shown in the paper. All  it does 
is distract from Corb’s accomplishments. Lets be clear, Corby has opened  
the door of H Maser performance for those that have a HP 5065A. Not all work 
is  done but a giant step has been accomplished, the challenge now is to 
continue  the work. In simple terms it gets down to keep the A/V slope from 
turning  upward. Work is going on off list to address some of the issues and 
maybe some  one is willing to contribute. But what the list at a whole can do 
is contribute  data as to HP 5065A performance. There are quite a few 5065A’s 
out there but  very little data besides HP spec. To better tackle the 
flattening of the curve,  aging, temperature sensitivity, barometric pressure 
sensitivity and even  humidity sensitivity has to be understood. It is 
unrealistic to get past 1 E-13  unless this is understood and compensated for. Also 
some of these parameters  will vary from unit to unit and some degree of 
tailoring to a particular unit  has to be considered in the design. Some tests 
have to be done by those members  that have access to a Maser. 
Also Corby  found out that units with older A3 modules did not get the 
performance boost but  replacement of A3 did get the super performance. That 
confirms my suspicion that  there is room for work on frequency generation. PRS 
10 does a direct  frequency generation. Somehow using the  step recovery 
diode as a mixer obviously works but is it optimum, or is there a  better way 
to generate the resonator frequency? What is key to get the best  signal and 
S/N ratio? 
When previously mentioning aging control, concern was  voiced as to getting 
in to the HP 5065A. Corby’s work gets to the hart of the  unit, the RVFR, 
but Corby has gone four for four.  Adding control will only move the two C  
field wires to the analog board and using 30 mA from the unit. Unit can 
easily  restored to its original condition as far as frequency control is  
concerned. 
Obviously the RVFR is the big differentiator in the  HP5065A and I know of 
no commercially available unit that even gets close but  once the work is 
complete a look at a FRK may be in order, I doubt it will ever  be as good, 
but there is room for a filter and the physics part is considerable  larger 
than today’s units.  Some  other units may be using a filter but the physics 
package is so small that  compromises had to be made and the goal was more 
cost than ultimate performance.  
It is up to the list to turn this in to a Maser like  performance with out 
mortgaging your home. 
Bert Kehren