[time-nuts] FE-5680A Voltage tolerance

Bob Camp lists at rtty.us
Fri Jan 20 12:18:14 EST 2012


Hi

I think there are two somewhat independent things flowing through this
thread. The first is - what is the real minimum voltage for this or that
level of operation. The second is - what is the voltage for *best*
operation. 

Every time I've been down this road before with an Rb, the answer to "what's
best" has been a well regulated supply at the minimum specified input
voltage. Varying the supply always seems to impact something and regulating
supplies is easy these days.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of EWKehren at aol.com
Sent: Friday, January 20, 2012 8:01 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] FE-5680A Voltage tolerance

Starting Sunday I will do some voltage tests, giving up on aging test, nine 
 weeks is long enough. I will se if the next one is as good, how ever I do  
not understand all the talk about running it at a lower voltage. Loosing  
regulation will definitely impact performance. I have not analysed my unit 
but a  13.3 V LDO was reported. In my opinion that says what the lower limit

is based  on sufficient margin for that regulator. What is wrong with 15 
Volt? I am  running the unit right out of the switcher no extra filtering
and I 
can say  based on my tests that it is good to 1 E-12. I also se a 4 Hz loop 
that  will be there with any kind of regulation. That is why I will include 
a clean up  OCXO with a 100 second analog filter. That OCXO will get special

attention in  its supply voltage regulation. Starting out with 15 Volt 
gives me enough head  room. I am using a $ 10   12 V 2 A switcher cranked up
to 
15  V.
Bert Kehren
 
 
In a message dated 1/20/2012 7:43:16 A.M. Eastern Standard Time,  
nerd at verizon.net writes:

It is  not surprising that many of these units work alright below their 
specified  
voltage.  I would imagine that the internal regulators, in addition  to 
dropping 
voltage, are also there to keep voltages stable, and thus help  with unit 
stability.  So, a unit may work fine, and be able to meet  stability specs, 
when 
operated slightly below the 15 volts, PROVIDED that  that lower input 
voltage is 
provided by a stable, regulated supply.   If I were the manufacturer, I 
would not 
want to have to rely on the supply  being perfect, I would want to do my 
own 
regulation as they have.   These are used in a system where the power 
supply 
drives many items and  there are voltage drops due to wiring, backplanes, 
traces, 
etc as well as  variations due to load changes.  You may be able to have 
one unit  
work fine slightly below spec'd voltage, but if you do that in a system or  
with 
an unregulated supply and all bets are off.  Give the unit  decent power 
within 
its specified input range and then that's one thing  you don't have to 
worry 
about further.

Peter


On  1/20/2012 6:09 AM, Rob Kimberley wrote:
> I've had one of mine running  on a bench supply for about 2 days now. Have
> just tried turning the  voltage down, and things started to get unstable 
at
> around 12.5V. It  didn't drop out of lock however until about 9V.
>
> Rob  Kimberley
>
> -----Original Message-----
> From:  time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>  Behalf Of Peter Gottlieb
> Sent: 20 January 2012 04:16
> To:  time-nuts at febo.com
> Subject: Re: [time-nuts] FE-5680A Voltage  tolerance
>
> When I got my first unit I hooked it up to my  protoboard power supply 
which
> is rated at 15 volts 0.5 amps and 5  volts 1 amp.  I was annoyed that it 
took
> about
> 10 minutes  to lock up until I realized the 15 volt supply was down near 
11.5
>  volts.  Oops.  Substituting my small B&K bench supply (good for  up to 3
> amps) resulted in a lock in under a couple of minutes.   Perhaps my unit's
> internal adjustments are still just about  right.  It would be nice to get
> the alignment procedure for the  thing, but I suppose, fat chance of that.
>
>  Peter
>
>
> On 1/19/2012 6:45 PM, gonzo . wrote:
>>  Experiment for the day.
>> I thought I'd follow Dons quote and see  how tolerant my unit is.
>> My benchmark is at 15.5V it locks in  about 3min.
>> I backed off the supply to 10.8V and the lock time  (from cold) is 8min.
>>
>> I thought this was interesting  given several people report they are 
unable
> to get a lock when running  lower voltage.
>> ian
>>           
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