[time-nuts] Ebay FE-5680A Rb: Are they that good?
smither at c-c-i.com
Thu Dec 8 15:04:51 EST 2011
Chuck Forsberg WA7KGX N2469R wrote:
> The price seems reasonable, esp. with free shipping.
> Does anyone have experience with these?
> Is the circuit board included?
I could not resist at < $40.00 delivered. Mine has been running for a couple of
weeks, but my measurements have been inconclusive (I suspect my setup is far
from ideal, especially the handling of the 10 MHz signal).
The unit I bought was mounted on a sheared off portion of a large PCB with a
ground plane / heat sink. It came with an extra DB9 connector and another
oscillator (Vectron, ~ 64MHz) thrown in.
I have not had time to see if my unit responds to programming from through
RS-232, but there is connectivity through the pins and there is a MAXIM RS-232
chip inside so I am optimistic.
When I first fired it up I simply compared its 10 MHz to a 10MHz OCXO that is
(manually) disciplined to GPS (another project!). I was impressed when after it
locked and settled for a few minutes the two 10MHz waveforms were stationary.
After a few minutes I could detect some slight drift, but I estimate the two
sources agreed to maybe 2 - 3 * 10^-11. That is about as good as I can keep my
OCXO so I'm not sure which of the two sources is better.
The unit is now mounted on a large heat sink (from a surplus 100W RF load). In
my lab the temperature at the top of the case has been running around 45 to 50 C.
I am redoing my test setup as I write. I have new power supplies and plan on
routing the 10MHz better.
My basic test will be to track the (averaged) time interval between a 1PPS from
an old Ref Tek 111A GPS clock and a 1PPS derived from the 5680A 10MHz.
After I have a few days of reasonable results I will report to the list.
Bob Smither, PhD Circuit Concepts, Inc.
America - born free, taxed to death ...
Smither at C-C-I.Com http://www.C-C-I.Com 281-331-2744(office)
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