[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...

Bob Camp kb8tq at n1k.org
Sun Nov 2 17:13:07 EST 2014


Hi

After spending some quality time with Mr. Google, I dug out some of the old UT+ information. The little beast does indeed forget everything it ever knew once you loose battery / super cap / whatever backup power. You can force a position, but it’s not persistent once you loose RAM.

If these GPSDO's normally ran with nothing connected to the Diag (HP commands) port, there may not be a way to force a survey solution into the GPS. If there is a Lucent command that does that over the PPS port, I’ve not seen mention of it. 

The approach may well have been to save what ever you had to RAM and if you lost it, back to square one. That’s not as crazy as it sounds. Having a cell site power down for 24 hours is a “big deal”. Having one out for several days, should be a very rare thing. If the super cap does the job for a few days, that may have been all the designers cared about. 

In TimeNut use, the situation isn’t really all that different. These boxes take a long time to get everything all worked out and stabilized. Turning them on and off is not a real good idea. Having them coast through a 24 hour power outage (position wise) is probably good enough for most of us. If you often have outages longer than a day, cancel my request to come play at your house ….

Having a nice modern GPS receiver outside the box might have it’s benefits in some cases. Getting the slave boxes figured out could be moving up on my list of things to do.

Bob

> On Nov 2, 2014, at 4:12 PM, GandalfG8--- via time-nuts <time-nuts at febo.com> wrote:
> 
> Ah, just found an Engineering Note in my files that again quotes 5uA at  
> 2.5V but also quotes 100uA at 5.0V, perhaps not too relevant at 3.1V but 
> that's  quite an increase.
> 
> The same document quotes the following specs for the optional onboard  
> lithium battery...
> 
> Voltage -- 3V
> Capacity -- 15mAh
>                  approximately  3 months between charges
> Recharge -- approximately 8 hours for a full charge
> Lifetime -- 5 Years minimum.
> 
> So I guess an onboard battery conversion might still be a viable  option.
> 
> Regards
> 
> Nigel
> GM8PZR  
> 
> 
> In a message dated 02/11/2014 21:01:55 GMT Standard Time, kb8tq at n1k.org  
> writes:
> 
> Hi
> 
> So then the question becomes - What is the real cutoff  voltage?
> 
> Your pair of AA’s will start off at 3.1V, but they will get to  2.5 long 
> before they are truly dead. Is the RAM gone at 2.5000 or 2.4 or  “about 2 volts
> ” ….
> 
> Bob
> 
>> On Nov 2, 2014, at 3:54 PM,  GandalfG8--- via time-nuts 
> <time-nuts at febo.com> wrote:
>> 
>> Hi Bob
>> 
>> The UT+ data sheet from 1998 quotes an external backup  supply of 2.5 to  
>> 5.35V with a drain of 5uA typical at 2.5  Volts.
>> 
>> Regards
>> 
>> Nigel
>> GM8PZR
>> 
>> 
>> In a message dated 02/11/2014 20:41:44 GMT Standard Time,  kb8tq at n1k.org  
>> writes:
>> 
>> Hi
>> 
>> The  numbers quoted earlier (and they sound right) were 20  uA at 2.5V. 
> That  
>> would be well under your 100uA. My *guess* is that self   discharge / 
> aging 
>> on a normal AA is going to limit things faster than  a 20 uA  drain. 
>> 
>> Now, if you have the more normal tiny  coin cell involved  with  1/10 or 
>> 1/100 that capacity and  much lower self discharge  ….
>> 
>> Bob
>> 
>>> On Nov 2, 2014, at 3:17 PM, Hal Murray  <hmurray at megapathdsl.net>  
> wrote:
>>> 
>>>> By the way the  z3801 is off most of  the year so the drains quite 
> small.
>>> 
>>> I  think  that's backwards.  The battery is only used when there is no 
>> power  to 
>>> the GPS module.
>>> 
>>> AAs are  roughly 2800 mA  hours.  There are 8760 hours in a year.   
> That's 
>> 319 
>>> microamp years.  (How's that for a SI  unit?)  So that's 3 years if  
> your 
>> GPS 
>>> module  takes 100 uA.  I think that's way high.   Anybody measured  it?  
>> There 
>>> is probably a strong temperature   component.
>>> 
>>> 
>>> -- 
>>> These are my  opinions.   I hate spam.
>>> 
>>> 
>>> 
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