Well done Bert, at last some sensible information regarding the multiplicity
of models of this Rb. I obtained my example from Fluke I for the higher
price - but he assures me that it is the RS232 programmable unit. I have not
had the opportunity to investigate it fully, but it would seem not to
require the additional 5 volt supply. The power requirements are 15 volts,
at initially 1.9 Amps, reducing to 680/700mA. Without any programming, it
provides a 1pps. signal from pin 6 of the 9-pin D connector. According to
my 53131A (locked to the GPS standard), the 1 pps is 1.000,000,001 s. The
modifications to the unit made by an earlier owner, suggests bringing the
(selected) signal out form the case, to a separate BNC, and another 9 pin D
for the RS232. Somebody on the list has suggested that it could do damage
to this variant, to connect 5 volts to pin 4, to date I have not done this,
Can any member confirm these details.
Thanks.
Roy
--------------------------------------------------
From: <ewkeh...@aol.com>
Sent: Monday, December 12, 2011 12:25 AM
To: <time-nuts@febo.com>
Subject: Re: [time-nuts] Ebay FE-5680A Rb: Connections and Features
Sorry I ever started this. In the past the FE5680's started out with a
50.255 MHz XTAL, some time in the 2002 2003 timeframe they switched to 60
MHz
using a DDS in the loop. All of these units can only be stepped in 7 E-13
steps limited by the resolution of the DDS. Having followed all the
listings
on this subject is it safe to assume that 99% of the units sold in the $
40
range are identical in that respect. At prior times there was and still
is
a unit available that from the 50.255 drives a DDS and a programmable
output is available at a premium price. All seem to be above $ 100.
Claims that
the 60 MHz units can be set in 1 E-13 is bogus and misleading. Maybe if
you dither the input, but since the loop is most likely digital I do not
know
what that will do.
Accept 7 E -13 or do as I will do, use the C field.
Pin 8 and 9 are RS 232.
Bert Kehren
In a message dated 12/11/2011 5:46:05 P.M. Eastern Standard Time,
snapp...@gmail.com writes:
Like many of you, I have seen these advertised on Ebay at good prices.
Also, like many of you, I am confused about the 'programmability' and
connections.
Many of them advertise these connections:-
PIN 1: INPUT +15V to +18V
PIN 2: GROUND
PIN 3: LOCK/UNLOCK (high = unlock)
PIN 4: INPUT +5V
PIN 5: GROUND
PIN 7: OUTPUT ( 10MHz sinewave )
Many of them also say "Digitally programmable to 1x10-13", with the above
connections. (Many of the sites seem to have the same descriptive text.)
On questioning one of them about how the programming was done, they
replied
"Not with this model; only with the more expensive one he sells !"
But from what I read in some of the time-nuts contributions, there is
sometimes (?) or often (?) also these connections:-
Pin 6 1 pps out
Pin 8 RS-232 Rx (into rubidium)
Pin 9 RS-232 Tx (from rubidium)
Can anyone tell me if they ALL have the MAX level shifter/driver chip
fitted, even though it may not be connected to the connector ? I don't
want full programmability, just 10 MHz frequency correction. Perhaps I
just
have to take pot luck when I buy ? What are my chances of getting one
with
the 'hidden' RS232 and 1PPS output ?
All advice appreciated.
Thanks.
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