Hello everyone, I have a 5680 which is failing to lock. My DDS frequency is 8388608Hz, but it's sweeping between about 8388638 and 8388740. My unit has 3 levels of PCBs in the DDS/VCO corner and there is no trimcap labeled C217. Does anyone know how to adjust the sweep center frequency on this type of 'triple decker' unit? Thanks, =Simon=

Hello Netizens ! Recently I obtain the "GPS FC" device. Its exactly as shown on the picture from the datasheet: http://www.gigatest.net/datum/gps-fc-e.pdf Now I try to test it. As far as I understood (in accordance with its specs.), it shold generate the 10Mhz signal as its locked to Satelites. I connected it through frequency divider (by 64) to my PC-based oscilloscope (yes, I know, I know, its not for "nuts"). I did preliminary tests with this divider with my T-Bolt and standalone DATUM OCXDO to make sure its working (see attached files). But that GPS FC still shows only some noise. In the datasheet, manufacturer mentioned about so-called "test board". Does anybody knows what is this board exactly ? For now I just connected power through the 1 MilliHenry coil and try to get signal from it through the divider which has 0.2nF capacitor in its input to eliminate DC). -- WBW, V.P.

Hi, I have a couple that look like the one in these pictures minus the the little frequency control board. http://www.flickr.com/photos/14336723@N08/sets/72157632394339366/ One of mine would not lock so what I did I looked at my other 5680A which is the type referred to in the tip about C217 and looked at how it is connected in relation to the crystal for the VCXO, which is very close to C217. In the ones that I have with the stacked cards this crystal is on the middle card with a little block of foam over it. Near this crystal is a trim cap C245 that seems to be connected the same way relative to the crystal and by adjusting it I was able to get mine to lock, but did find the adjustment to be a bit twitchy and since it is on the middle card, you need to remove the top one every time you want to tweak it a bit. The one that I have are marked with option 57 and instead of having a flange around the edge like many of the telecom surplus ones it is mounted on a piece of 1/4" aluminum plate. The top card has a PIC on it and there is a RS232 level converter chip there but it looks like the connection only go to the 5 pin connector next to the SP232ACT RS232 chip. This one does not require external +5V and in fact bring out the 10MHz on pin 4 where others seem to connect +5V. there does not appear to be any PPS output either. These also have a cutout to expose the 15 pin connector that is on the base board in front of the physics package. Paul. On 2/17/14 11:03 PM, Simon Lyons wrote: > Hello everyone, > > I have a 5680 which is failing to lock. My DDS frequency is 8388608Hz, > but it's sweeping between about 8388638 and 8388740. My unit has 3 > levels of PCBs in the DDS/VCO corner and there is no trimcap labeled > C217. Does anyone know how to adjust the sweep center frequency on > this type of 'triple decker' unit? > > Thanks, > > =Simon= > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.