[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
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
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
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
The 25 pin details to follow, and if this isn't the same module then humble
apologies in advance for the wasted bandwidth:-)
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