[time-nuts] FE-5680A Results so far

Chuck Forsberg WA7KGX N2469R caf at omen.com
Wed Dec 28 21:08:39 UTC 2011


My FE5680A came with a 0 offset.   For my unit the correct offset is 
something
like -1343.  I sometimes set an offset of 0 to slew the phase difference 
to 180,
at which time I change it to -1343 (give or take).

If you take an FE5680a to a friend's lab and "dial it in" the act of 
powering it down
and transporting it back could throw it off by 1e-9 or more.

The thing I'm learning here is that everything affects everything when 
working at this
level of resolution.  Remember the stories about solar flares or 
something affecting
the rate of radioactive decay?


On 12/28/2011 11:05 AM, ws at Yahoo wrote:
> Chris posted:
>> So how to test it?  anyone have any creative ideas?
>
> That's easy, get a couple more of them.
> The using a scope, trigger on one unit and watch the phase drift of 
> the others.
> With most basic scopes you can detect sub ns phase changes of 10MHz 
> signals this way, which allows you to see a 1e-11 frequency difference 
> in a couple minutes. (1ns/sec change = 1e-9 freq offset)
>
> Or you could use the basic x y display and count how many minutes it 
> takes to complete one cycle.
> That will allow you to see the same resolution after a few hours. (a 
> 100ns cycle per sec = 1e-7 freq offset)
>
> ws
>
> ************
> *************
>
> [time-nuts] FE-5680A Results so far
> Chris Albertson albertson.chris at gmail.com
> Wed Dec 28 18:21:54 UTC 2011
>
> Just got my fe5680 yesterday.   Seems to work but the fe5680 is the most
> accurate reference I have.  So how to test it?   I plan to buy a
> Thunderbolt but until then, anyone have any creative ideas?
>
> I have an HP5328A with unknown calibration.  It reads 10,000,026 Hz
> I have an FCC 1 kit I assembled a few years ago and it says 9,999,993 Hz.
> (I can make the FCC1 read exactly 10MHz if I place it on top of the hot
> FE5680, the FCC1 is very temperature sensitive.
> My old Tek scope says the period is "about" 0.1 uS and the sine wave 
> looks
> pretty good.
>
> BTW, 5 VDC is 76.5 mA with RS232 not connected.    15 VDC is 1.5 ~ 0.8 A.
> The unit does get warm.  A 3/16 x 5 x 16 inch aluminum plate worked is a
> "good enough" heat sink.
>
>
> Going to have to get a Thunderbolt.  I have an Oncore UT+ the provides a
> good pulse per second but that will not help
>
> Chris Albertson
> Redondo Beach, California
>
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-- 
Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
   Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430





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