On 04/22/2011 11:37 PM, WB6BNQ wrote:
Hi Pete,
As Bob, K6RTM, pointed out the Thunderbolt and the Rubidium are two different
animals all together.
True, you can treat a Rubidium like it was a normal crystal oscillator, but it
is
not the same. The Rubidium has a definite life span, the more you run it the
less
the life. A high quality crystal oscillator, on the other hand, just gets
better
the longer you leave it on. Aside from nominal electrical component failures,
the
crystal blank in a properly designed circuit has no short term failure
mechanism and
will last for decades with constant applied power. The Rubidium’s life span
is, at
best, 10 years. The question is how long was it running before you got it ?
I do not agree here. The main failure mechanism I've seen beyond normal
electronic faults due to rubidium lamp, and it doesn't take much time
effort and skills to solve that particular issue. It's not a wear
mechanism as such, more a unfortunate displacement issue, which can be
sufficiently reversed. It is a problem inherent to a popular lamp
design, which is not to say it is true for all rubidium lamps either...
As for your project boxes, I would use the rack mounted box to house the
Thunderbolt, distribution amps and perhaps a couple of other oscillators (like
the
hp 10811) along with quality power sources. Because crystal oscillators like a
constant operating condition, do consider battery power for the lab to handle
those
occasional mains power drops.
I would use the portable box for the Rubidium oscillator and include a battery
option depending upon your intent. The emphasis should be to have very quiet
and
stable power supplies for both projects. Even batteries have a fair amount of
noise
so make the mains power (and battery) voltage high enough to allow for running a
quality regulation circuit.
Recall that Rubidiums also like stable temperature. Possibly a
controlled fan could be used to control the temperature of the rubidium.
Passive radiation through heat-sink isn't the best solution. Raising the
temperature of the cooling surface but keeping a tighter control of its
temperature lowers the need to consume power by the heaters and will
lower the current through transistors...
Cheers,
Magnus
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