[time-nuts] Things to look for when buying a few FE-5680A's?
rexa at sonic.net
Thu Jan 26 02:21:28 EST 2012
On 1/22/2012 9:49 AM, Chris Albertson wrote:
> The current batch of (about) $40 units are different from what was
> available a year ago. These new ones require 5V DC input in addition
> to 15V and can only be programmed via RS232 a few Hz away from 10MHz.
> So they are only good for use as a 10MHz reference
For historical accuracy, in Jan 2005, I bought an FE-5680A which didn't
work with just a 15 V supply. After some hacking, I think I was the
first (at least on this list) to figure out that it also needed 5V on
one of the pins to operate. I was not able to program that one. Though
reminded by these many recent emails, I haven't yet pulled it out of my
stash to see if I missed something when I tried to communicate on RS-232
So the *new* ones are not that new, but they are newer than the ones,
more commonly known before 2005, that worked on only 15 V and could be
programmed over a wide frequency output range.
Over the years, one thing is quite obvious -- Frequency Electronics Inc.
(FEI) made many similar but different versions of the FE-5680A. There
seems to be no definitive way to distinguish versions that have no
external physical differences (like an sma output). Also, FEI has not
been responsive, to my knowledge, to any questions from us surplus
It is fortunate that this latest round of FE-5680A's seem to be
consistent in characteristics and many clever people have derived a lot
of details about their internals and programmatic interface. It is great
that the current available surplus product seems consistent, but be
aware that there were many indistinguishable iterations of the 5680A on
the surplus market over the last decade or so.
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