[time-nuts] LPRO101 orientation vs lock

Neville Michie namichie at gmail.com
Thu Sep 16 09:41:55 UTC 2010

there are two obvious causes of lost lock,
wandering off beyond the range of the voltage controlled crystal  
local oscillator, not an OXCO, which is swept through the atomic  
response frequency,
and the failure of the rubidium lamp at the end of its life.
The oscillator sweeping voltage (pin 9) has limits and if the correct  
frequency is not in the range lock is not possible. If the VCXO has  
drifted it may be possible to add/remove a tiny amount of capacitance  
from the oscillator circuit to get it in range.
The rubidium lamp voltage (pin 5) is between 3 (low) and 14 volts, at  
the end of the lamp life it goes low.
This is all from my memory, the detail is in the User's guide and  
integration guidelines.
cheers, Neville Michie

On 16/09/2010, at 4:51 PM, d.seiter at comcast.net wrote:

> I got one of the ebay LPRO-101s about 6 months ago and played with  
> it for a while, but had problems maintaining a lock. First of all,  
> it has a heat sink bolted to the bottom that is just a little  
> larger than the LPRO itself, including being about 1.25" thick( 1"  
> fins). Typical frequency when locked is 10,000,000.007 on a 5360A  
> clocked by a Z3801A.
> Both then and now, it takes about 45 seconds to lock from cold, and  
> will stay locked for about 45 minutes. I found that in the position  
> with the heat sink on the bottom will stay locked the longest (up  
> to a few days), but then it becomes intermittent. Other positions  
> will lock for a while, but bottom down always works the longest.
> For those of you who employed these in TM5xx or similar plugins,  
> did you have lock issues? Is my unit just old?
> Dave
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