[time-nuts] Housing LPRO and Thunderbolt together

[Magnus Danielson]

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