Re: [time-nuts] Datum TS2100 10MHz frequency drift
Philip Zahariev via time-nuts kirjoitti: Unfortunately I'm not happy with results because 10 MHz output signal after GPS lock (both leds on front "Locked" and "tracking" are "ON") has frequency drift (phase shift) with period around one second plus minus ~18 deg (+-5 ns) compared to other 10 MHz. I measure this by 2 channel scope on 10 nS sweep, first channel connected to TS2100 10 Yes it works like that and it seems to update the DAC value once per second. Frequency wobbling is perfectly in sync with PPS output, which is kind of logical. If you look TS2100 manual it says "stand alone time server" which means it's designed to serve as time standard - not as frequency standard. If you need stable frequency then you should try with Rubidium oscillator or with some other GPS unit. For example Thunderbolt has much more stable frequency output than TS2100, but it's also a timing receiver, not frequency standard. However with OCXO and GPS upgrades you will get more than 10 times better timing than original TS2100. Without upgrades the TS2100 PPS is just below 1 microsecond, with MTI OCXO and Heol Design N024 GPS board it's about +-50 ns. So it's relatively good for every day timing purposes.. :) Of course you could try could be to play with timing constant settings but I don't think it would help anything if the DAC is still written once per second. But if you find better values please let us know! Best regards, -- 73s! Esa OH4KJU ___ 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.
Re: [time-nuts] Datum TS2100 10MHz frequency drift
Philip wrote: few weeks ago I acquire TS2100GPS with TCXO. Few days ago receive MTI OCXO and install in device. After replacement change gain and filter constant as described byJason Rabel's post from 9/26/2010 Looking at that post in the list archive, it does not appear to describe any particular loop tuning solution -- Jason was asking a question regarding (i) whether the tuning parameters available in the 2100 would support an OCXO, and (ii) if so, what parameters should he use for his specific OCXO. It does not appear that he received any responses to his question. Unfortunately I'm not happy with results because 10 MHz output signal after GPS lock (both leds on front "Locked" and "tracking" are "ON") has frequency drift (phase shift) with period around one second plus minus ~18 deg (+-5 ns) compared to other 10 MHz. The PLL control loop is apparently unstable with the parameters you have programmed. You need to determine, first, whether the parameters available are sufficient to accommodate an OCXO and, if so, what specific parameters you need to program to achieve optimal (not just basically stable) operation. In other words, YOU have to answer Jason's question. Best regards, Charles ___ 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.
[time-nuts] Datum TS2100 10MHz frequency drift
Hello Time-nuts group, few weeks ago I acquire TS2100GPS with TCXO. Few days ago receive MTI OCXO and install in device. After replacement change gain and filter constant as described byJason Rabel's post from 9/26/2010 Unfortunately I'm not happy with results because 10 MHz output signal after GPS lock (both leds on front "Locked" and "tracking" are "ON") has frequency drift (phase shift) with period around one second plus minus ~18 deg (+-5 ns) compared to other 10 MHz. I measure this by 2 channel scope on 10 nS sweep, first channel connected to TS2100 10 MHz output and second channel connected to 10 MHz from other GPSDO and sync by second channel. I'm sure that issue is in TS2100 because if disconnect GPS antenna frequency jumping disappear and frequency is more or less on spot (very very slow movement of one sinusoid against other) Also monitoring EFC voltage to OCXO with voltmeter has the same behavior confirmed by command "root timing util tfp 0" - again jumping up and down between 0xb4b5 and 0xb4c9.Firmware of TS2100 was 3.1 and "upgrade" to 4.1 does not solve problem. I suspect algorithm for adjustment of OCXO, but can't believe that this is normal. Can someone confirm that frequency change is not normal behavior. And of coarse I'm open for any suggestion how to solve problem. ___ 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.
