Thank you Nigel for your comment. Now I understand the reason why it may be useful to have this additional external link. In the counter is fitted an oscillator model 10544A (instead of a more known 10811), but I think that it is the original one because the date code of the serial number is a bit old (year 1981). At that date, the 10544 was still in use. Observing carefully the way in which the internal connections to the Ref In and Out are made, I notice that wires, insulating material and sockets are different from the original HP's. So it seems actually to be a user made modification not related to option C19. Good bye Luca
2013/8/21 <[email protected]>: > Hi Luca > > There are other items of HP equipment fitted with Ref Out and Ref In > terminals joined by an external link, with the intention that the link is > removed to connect an external standard to the Ref In terminal, but in a > "normal" > 5345A the external reference is used to phase lock the internal oscillator > which means that the unit can't work from an external reference if the > internal 10MHz oscillator has been removed. > > However, I found some time ago that it is possible, just by fitting a > single link internally, to drive the counter via an external reference even if > the internal standard has been removed so I'm guessing that the internal > standard on this one might have been removed at some time and a previous > owner has fitted a non original internal standard with a similar provision to > bypass the normal arrangement. > > It should be fairly easy to check just by looking to see if the original > HP oscillator is still fitted or whether a different one has been added. > > Whether or not this relates to the Option C19 I don't know. > > Regards > > Nigel > GM8PZR > > > In a message dated 21/08/2013 17:00:21 GMT Daylight Time, [email protected] > writes: > > Dear all, > > I have bought an HP 5345A. It’s ok and I’m very glad. On the rear > panel it is wrote "OPTION C19" (a little bit strange!) and there are > two additional BNC installed on the little panel normally used to > place the HPIB connector when present. > > These 2 BNCs are named REF OUT and REF IN and there is a jumper cable > that connects the output to the input. > > It seems to be a modification made by some user (very strange: I can’t > understand why to place an extra auxiliary bypass for the 10 MHz > reference). > > Do you have an idea about this strange modification and about the > strange option C19? Could it be a custom option? Could the option C19 > and the 2 BNC for the reference be related? > > Thanks > > Bye > > Luca – IW2LJE – Milano – Italy > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
