[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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