In a message dated 4/29/2013 6:34:24 P.M. Eastern Daylight Time,
bruce.griffi...@xtra.co.nz writes:
Since performance improves as the bandwidth of the "lamp" spectrum
decreases its not unreasonble to suggest that a suitable laser source
may improve performance further.
The following paper (and theoretical considerations) indicate that your
conclusions regarding the potential performance of a laser pumped
rubidium standard are incorrect.
http://tf.boulder.nist.gov/general/pdf/1219.pdf
The addition of second harmonic traps tuned to the 2nd harmonic of the
modulation frequency of the resonance interrogation signals should
improve the performance considerably.
Bruce
ewkeh...@aol.com wrote:
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
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