[time-nuts] Ebay FE-5680A Rb: Connections and Features
Roy Phillips
phill.r1 at btinternet.com
Sun Jan 8 12:57:17 UTC 2012
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: <EWKehren at aol.com>
Sent: Monday, December 12, 2011 12:25 AM
To: <time-nuts at 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,
> snappa09 at 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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