[time-nuts] Lucent RFG-RB

[Richard H McCorkle]

I'm sure Lucent engineers spent quite a bit of effort designing that metal
box to keep the rubidium temperature as low as possible for extended life.
If the rubidium is used in a different enclosure pay special attention to
thermal
conditions as the life of the rubidium is reduced with increasing
temperature.
If it is warm to the touch while operating you are not getting the most
useful
life out of the unit. The LPRO manual shows this as the mean time before
failure versus operating temperature:

       Temp                MTBF
20°C     68°F    381,000    43.5 yrs
25°C     77°F    351,000    40.1 yrs
30°C     86°F    320,000    36.5 yrs
40°C    104°F   253,000    28.9 yrs
50°C    122°F   189,000    21.6 yrs
60°C    140°F   134,000    15.3 yrs

I ended up building by own controller and mounting it inside the Lucent box,
removed their front panel and mounted the box to my front panel to keep the
thermal design the same and take advantage of Lucent's thermal engineering.

Have fun!
Richard

----- Original Message ----- 
From: "Rex" <rexa at sonic.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Thursday, December 28, 2006 1:28 AM
Subject: Re: [time-nuts] Lucent RFG-RB


> On Thu, 28 Dec 2006 21:49:59 +1300, Dr Bruce Griffiths
> <bruce.griffiths at xtra.co.nz> wrote:
>
> >Rex wrote:
>
> >> The 15 MHz generation looks very similar to the other boad I described
> >> in another message on an FRS-C unit. The active source again seems to
> >> come from an Altera PLD. Maybe it divides 10 MHz by two, and (guess)
> >> narrows the pulse for better 3rd harmonic?
> >
> >Narrowing the pulse width does little for the amplitude of the third
> >harmonic component.
> >There's already plenty with a 50% duty cycle square wave.
> >A waveform with duty duty cycle of 1/6 has the same 3rd hamonic
> >component amplitude as a 50% duty cycle waveform.
> >Narrowing the pulse to a very small duty cycle tends to flatten the the
> >frequency comb whilst reducing the amplitude of all components.
> >see:
> >http://www.wenzel.com/pdffiles/choose.pdf
> >
> >Bruce
>
> Yeah, the harmonic amplitudes vs pulse width chart in that Wenzel doc is
> exactly what I was thinking about when I wrote. I didn't actually look
> at it though. I see now 3rd is good at 50% and the other harmonics are
> mostly low. Guess I was trying to find a reason why the source for the
> 15 MHz filter seemed to be coming out of a PLD. Maybe it's doing other
> more complicated functions that I haven't yet figured out, and divide by
> 2 for the 10 MHz was just easy to throw in. Like I said, seems about
> like the implementation I saw in that other board. Never did work out
> all the PLD was doing there either. PLDs are hard to guess out.
>
> I guess, when I get around to powering it up, I can put a scope on the
> signal at that point and see if it is just 5 MHz square.
>
> Good chance I'll just use the LPRO anyway and dump the rest of the box.
> Can't think of a reason why I need 15 MHz and I can't see much else
> useful in the rest of the supporting circuitry.
>
> The metal box is kind of interesting.
>
>
>
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