In my introductory email to the group, I mentioned that I was disappointed in the GPS receiver I built from James Miller's design.
I must clarify what I said with apologies to James for any misunderstanding I might have created about his design! The receiver has an intermittent problem and I have not been able to track down the cause. The measurement of time to this level of precision is new to me. As of now, I have few pieces of test equipment suited to the task. What I do have, I either built, or bought broken and repaired. The problems I am experiencing with the GPS receiver are almost impossible to track down because they are intermittent, they occur infrequently, and they involve measurements to a level of precision I am not well equipped to make. At this point, I do not know what is causing these brief losses of stability. They last for less than a few minutes as near as I can tell. My next step, which is to try to monitor the output voltage of the PLL and correlate it with the loss of stability, requires a way to log voltages. Unfortunately the two GPIB Digital Multimeters I own both broke before I could do this. Until I know what part of my GPS receiver is causing the trouble I should not speculate on the cause. What I can say is that I followed James design to the letter. It uses the Rockwell Jupiter TU30-D140 Receiver, James' PLL PCB, the IsoTemp OCXO134-10, and a Symmetricom 58532 GPS L1 Reference antenna mounted on my roof and connected to the receiver through low loss cable. The entire circuit is professionally mounted into a Tektronix TM500 Prototyping Plug-in that is powered by a TM501 power supply that is, in turn, plugged into an Uninterruptible Power Supply. One feature I wish this design had is an indication of when the output is locked to the GPS satellites. I must admit, I could not figure out a simple way to do this. I have since then come across a circuit that purports to do this. However, until I solve the intermittent problem I have been reluctant to add this circuit to the design. Dennis ------------------------------------------------------------------------ > * Two years ago I built my own GPS frequency standard based on the > design by James Miller but it has been a big disappointment. I started > to suspect it was not reliable so I wrote a LabView program to compare > it to the reference outputs of two ArgoSystems AS210 systems I found > on eBay and restored. The LabView program confirmed my suspicions that > the GPS receiver was briefly loosing its stability for brief periods > several times a week. _______________________________________________ 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.
