Re: [time-nuts] Couple of questions for Racal 1992 owners
I have two 1992, and actually one has to terminate the output to see the real waveform. They have both the 04E option, that I believe is a nice one. In long term measurements, I've found that mine have an aging rate in the range of 1x10E-10 per day, or better (compared to Rb). The crystal is cut to 5 MHz, then doubled. The time required to stabilize after power on is normal. Antonio I8IOV My 1992 has a similarly ugly reference output - until I terminate it. Then it's a fairly nice square wave between 0 and 1 volt. Rise fall times are in the range of 5 ns. The manual doesn't state what the wave shape is, only that it's 600 mVp-p into 50 ohms. I have a brochure that says TTL levels giving approx. 1Vp-p into 50 ohms. My phase measurements also have a similar amount of 'noise' to yours. Which timebase does yours have? I've got option 4E (similar to 4B). Although the timebase appears to be stable, I've noticed that the counter drifts about 5e-9 during warmup, even when the oscillator has been on standby for many days. It takes a couple of hours to settle down. Does yours do anything similar? Ed John Green wrote: Just acquired a used 1992 off eBay. Excellent, almost like new with manual and even spare fuses. I noticed that the internal reference's waveform is more like a nasty sawtooth than a nice sine wave. Is that normal? Also, when I hook my GPSDO through a two way splitter and two different length cables and measure phase, I get a +\- 3 LSD ambiguity. Is that about right? ___ 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 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 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] Couple of questions for Racal 1992 owners
-Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Thursday, August 27, 2009 12:06 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Couple of questions for Racal 1992 owners Thanks for the info Antonio. Racal didn't spec the warmup characteristics of the counter as a whole and it seemed a little odd that the warmup drift for the counter was as large as 10 days of oscillator drift. Ed Intuitively, this wouldn't surprise me. You set the OCXO up so that the temperature is somewhat higher than the highest expected ambient (so, say, it's at 60C) and pick a crystal that has a flat freq/temp characteristic near there. So, when you turn on, your crystal is at, say, 25C, where the slope of the freq/temp curve is pretty steep. I'll bet someone has some curves out there that could give a quick order of magnitude estimate... I have a poor quality chart here that shows an AT cut with about 40 ppm change for a 50 degree C change, and an SC changes about 5 ppm over the same span. Since a decent oscillator has aging of small ppm/year, that's orders of magnitude bigger for the temperature effect. Is this a SC or an AT cut? ___ 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] Couple of questions for Racal 1992 owners
Thanks for the info Antonio. Racal didn't spec the warmup characteristics of the counter as a whole and it seemed a little odd that the warmup drift for the counter was as large as 10 days of oscillator drift. Ed iov...@inwind.it wrote: I have two 1992, and actually one has to terminate the output to see the real waveform. They have both the 04E option, that I believe is a nice one. In long term measurements, I've found that mine have an aging rate in the range of 1x10E-10 per day, or better (compared to Rb). The crystal is cut to 5 MHz, then doubled. The time required to stabilize after power on is normal. Antonio I8IOV My 1992 has a similarly ugly reference output - until I terminate it. Then it's a fairly nice square wave between 0 and 1 volt. Rise fall times are in the range of 5 ns. The manual doesn't state what the wave shape is, only that it's 600 mVp-p into 50 ohms. I have a brochure that says TTL levels giving approx. 1Vp-p into 50 ohms. My phase measurements also have a similar amount of 'noise' to yours. Which timebase does yours have? I've got option 4E (similar to 4B). Although the timebase appears to be stable, I've noticed that the counter drifts about 5e-9 during warmup, even when the oscillator has been on standby for many days. It takes a couple of hours to settle down. Does yours do anything similar? Ed John Green wrote: Just acquired a used 1992 off eBay. Excellent, almost like new with manual and even spare fuses. I noticed that the internal reference's waveform is more like a nasty sawtooth than a nice sine wave. Is that normal? Also, when I hook my GPSDO through a two way splitter and two different length cables and measure phase, I get a +\- 3 LSD ambiguity. Is that about right? ___ 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] Couple of questions for Racal 1992 owners
I should of added Yes, It's normal for phase measurement to be 3 counts OR anything else depending on the frequency you are measuring. The unit measures Time delay to 1ns, and calculates Phase which can be any number depending on Freq. Use Time interval not phase to see what the noise is. My typical Dana 1992 performance with the good OXCO is: (sample size of ONE) 4 year average aging rate 0.2 e-10 /day (Attached) Day to Day uncertainty around 3 e-10 (same conditions each day, morning at same room temp, reading 1 min after turn-on from standby) Turn on warm-up drift First 15 sec =1e-10, First 1 min = 2 e-10 Warm up 1+ hr about =1e-9 OSC stability throughout the day after 1 hr turn (due to changing line, room temp, etc about 5e-10) Time interval noise measurement of less than 1 ns (no 1 count jitter about 1/2 the time as the delay between signals change). (Using two Square wave inputs from separate low noise sources , the first is 100 Hz the second is 100KHz, so max of 100us delay.) Turn on data above is Always from standby, and When not using the unit, it is always in standby, except for a couple of times per year when power fails. For your ambiguity test to eliminate LOTS of possible external noise sources, try feeding it a single good square wave in the range of 10 Hz to 10MHz, (Rise fall times in the 5ns range) Trigger on common, start slope to positive, stop slop set to neg, Use and the trigger level of each channel to cause fine delay adjustment of + - 5ns between signals. Mine has noise mostly under 1 ns count. i.e can adj the trigger level so jitter is less than or equal to 1ns. I have not looked at OSC out for a long time, most data above is from measuring the 10 sec freq average of a 10MHz. GPS tracked Osc ws *** From: iov...@inwind.it I have two 1992, and actually one has to terminate the output to see the real waveform. They have both the 04E option, that I believe is a nice one. In long term measurements, I've found that mine have an aging rate in the range of 1x10E-10 per day, or better (compared to Rb). The crystal is cut to 5 MHz, then doubled. The time required to stabilize after power on is normal. Antonio I8IOV *** My 1992 has a similarly ugly reference output - until I terminate it. Then it's a fairly nice square wave between 0 and 1 volt. Rise fall times are in the range of 5 ns. The manual doesn't state what the wave shape is, only that it's 600 mVp-p into 50 ohms. I have a brochure that says TTL levels giving approx. 1Vp-p into 50 ohms. My phase measurements also have a similar amount of 'noise' to yours. Which timebase does yours have? I've got option 4E (similar to 4B). Although the timebase appears to be stable, I've noticed that the counter drifts about 5e-9 during warmup, even when the oscillator has been on standby for many days. It takes a couple of hours to settle down. Does yours do anything similar? Ed * John Green wrote: Just acquired a used 1992 off eBay. Excellent, almost like new with manual and even spare fuses. I noticed that the internal reference's waveform is more like a nasty sawtooth than a nice sine wave. Is that normal? Also, when I hook my GPSDO through a two way splitter and two different length cables and measure phase, I get a +\- 3 LSD ambiguity. Is that about right? ___ ___ 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] Couple of questions for Racal 1992 owners
Lux, Jim (337C) wrote: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ed Palmer Sent: Thursday, August 27, 2009 12:06 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Couple of questions for Racal 1992 owners Thanks for the info Antonio. Racal didn't spec the warmup characteristics of the counter as a whole and it seemed a little odd that the warmup drift for the counter was as large as 10 days of oscillator drift. Ed Intuitively, this wouldn't surprise me. You set the OCXO up so that the temperature is somewhat higher than the highest expected ambient (so, say, it's at 60C) and pick a crystal that has a flat freq/temp characteristic near there. So, when you turn on, your crystal is at, say, 25C, where the slope of the freq/temp curve is pretty steep. I'll bet someone has some curves out there that could give a quick order of magnitude estimate... I have a poor quality chart here that shows an AT cut with about 40 ppm change for a 50 degree C change, and an SC changes about 5 ppm over the same span. Since a decent oscillator has aging of small ppm/year, that's orders of magnitude bigger for the temperature effect. Is this a SC or an AT cut? I agree with what you've said, but on the 1991/1992 counter, there's a standby function which keeps the oscillator hot, to avoid the issue you've stated above. So the 10 days worth of drift when you turn the counter on is just due to the counter warming up, not the oscillator. The oscillators that I have (opt. 4A and 4E) are both AT crystals. This isn't stated anywhere that I can find, but the frequency at startup is in the range of 20ppm high which is consistent with an AT cut crystal. Ed ___ 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] Couple of questions for Racal 1992 owners
Just acquired a used 1992 off eBay. Excellent, almost like new with manual and even spare fuses. I noticed that the internal reference's waveform is more like a nasty sawtooth than a nice sine wave. Is that normal? Also, when I hook my GPSDO through a two way splitter and two different length cables and measure phase, I get a +\- 3 LSD ambiguity. Is that about right? ___ 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] Couple of questions for Racal 1992 owners
My 1992 has a similarly ugly reference output - until I terminate it. Then it's a fairly nice square wave between 0 and 1 volt. Rise fall times are in the range of 5 ns. The manual doesn't state what the wave shape is, only that it's 600 mVp-p into 50 ohms. I have a brochure that says TTL levels giving approx. 1Vp-p into 50 ohms. My phase measurements also have a similar amount of 'noise' to yours. Which timebase does yours have? I've got option 4E (similar to 4B). Although the timebase appears to be stable, I've noticed that the counter drifts about 5e-9 during warmup, even when the oscillator has been on standby for many days. It takes a couple of hours to settle down. Does yours do anything similar? Ed John Green wrote: Just acquired a used 1992 off eBay. Excellent, almost like new with manual and even spare fuses. I noticed that the internal reference's waveform is more like a nasty sawtooth than a nice sine wave. Is that normal? Also, when I hook my GPSDO through a two way splitter and two different length cables and measure phase, I get a +\- 3 LSD ambiguity. Is that about right? ___ 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 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.
