[time-nuts] [Mw] Efratom 10MHZ Rubidium FREQUENCY Standard FRS-C

GandalfG8 at aol.com GandalfG8 at aol.com
Tue Jun 16 05:48:28 EDT 2009

In a message dated 16/06/2009 09:04:25 GMT Daylight Time, didier at cox.net  

>  -----Original Message-----
> From: microwave-bounces at lists.valinet.com  
> [mailto:microwave-bounces at lists.valinet.com] On Behalf Of Randy  Bynum
> Sent: Monday, June 15, 2009 9:03 PM
> To:  microwave at echo.valinet.com
> Subject: [Mw] Efratom 10MHZ Rubidium  FREQUENCY Standard FRS-C
> Does anyone have the pin connections  for this frequency 
> standard? There is a male DB-25 connector on it  and the box 
> has the 3 TNC female RF connectors.
> All in a box  about 4X4X3.

I didn't see this message until Didier posted his reply but this sounds  
like it could be the Lucent module containing the FRS itself plus two  
interface boards.
If it is then I asked a similar question recently and Bill Ezell was kind  
enough to provide the connection information for the DB25 which  I'll 
forward to the list again after sending this to save you having to  look for it in 
the archives.
Note that Bill's list describes pin 20 as ground but on my unit  it links 
to an internal resister, purpose unknown, and not ground. The only  
connections I've used are the +24 power connections on pins 1 and 2, and ground  on 
pins 3 and 4.
The only advantage I found in using the complete module, or the PCBs in my  
case as I don't have the box, was havng the RF output provided on one of  
the TNC connectors rather than having to rely on a take off point from the  
interface PCB that connects directly to the FRS. The interface board with the 
 DB25 and TNCs serves no other obvious useful purpose if only wanting to 
use  the FRS and it adds 200 to 300 mA to the supply current.
In the longer term, if this is the same unit, I would recommend not using  
either of the PCBs but removing the FRS mating connector from the otherwise  
unpopulated "bridge" PCB and using that to make direct connections to the 
FRS  itself.
Didier's manual will have all the necessary information for that.
As per the assorted and very wide ranging recent discussions, the FRS  
should be mounted on some form of heatsink:-)
This applies even if kept in that outer box,
Viewing the unit on the connectors with the DB25 at the top, as marked on  
the PCB the DB25 is J1, the bottom left hand TNC is J2, the middle TNC is 
J4,  and the right hand TNC, slightly above the others, is J3.
TNC connections are....
J2 -- 15MHz output when used in original Lucent kit.
J3 -- Direct connection to FRS 10MHz output.
J4 -- Also 10 MHz output. Bill describes it as buffered, I metered 50 ohms  
between this and J3 when unpoweredso not sure if it's actively buffered or 
just  padded.
The 25 pin details to follow, and if this isn't the same module then humble 
 apologies in advance for the wasted bandwidth:-)

More information about the time-nuts mailing list