Re: [time-nuts] retry: PRS10 has spurious frequencies
Henk ten Pierick wrote: > On Apr 25, 2007, at 23:38, Dave Brown wrote: > > >> Henk >> Do any of the spurious signals show on the SA with a search antenna >> (located in your lab environment)connected instead of the PRS10? >> DaveB >> > > > No, they are not. I can see spurious if and only if the PRS10 is > powered. When I open the PRS10 and search with a loop antenna, then I > see the whole spectrum up to 600MHz. Most of the power comes from the > board with the micro which runs at 10MHz. I expect that there is a > parasitic coupling of this micro 10MHz to the PRS10 output. This can > explain why the spurious level increases with frequency to higher > than the spectrum analyzer noise level at say 500MHz. The micro slew > rate can explain why it decreases again into the noise above 700MHz. > The spurious is only there if the micro runs. It is not clear to me > why I can see this spurious and other PRS10 owners can not. May be a > different run or version of the PRS10. My PRS10 has serial 5099. > > Henk > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Henk If indeed the micro is the source of the spurious frequencies that other PRS10's do not exhibit, then either you've got an unusually fast micro or there is something wrong/different in the micro supply decoupling and/or EMI filtering. The PCB layout could differ or different or even extra components may have been used in the other PRS10's. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
On Apr 25, 2007, at 23:38, Dave Brown wrote: > Henk > Do any of the spurious signals show on the SA with a search antenna > (located in your lab environment)connected instead of the PRS10? > DaveB No, they are not. I can see spurious if and only if the PRS10 is powered. When I open the PRS10 and search with a loop antenna, then I see the whole spectrum up to 600MHz. Most of the power comes from the board with the micro which runs at 10MHz. I expect that there is a parasitic coupling of this micro 10MHz to the PRS10 output. This can explain why the spurious level increases with frequency to higher than the spectrum analyzer noise level at say 500MHz. The micro slew rate can explain why it decreases again into the noise above 700MHz. The spurious is only there if the micro runs. It is not clear to me why I can see this spurious and other PRS10 owners can not. May be a different run or version of the PRS10. My PRS10 has serial 5099. Henk ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Henk Do any of the spurious signals show on the SA with a search antenna (located in your lab environment)connected instead of the PRS10? DaveB - Original Message - From: "Henk ten Pierick" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" Sent: Thursday, April 26, 2007 8:42 AM Subject: Re: [time-nuts] retry: PRS10 has spurious frequencies > Hi Poul-Henning, > > 1. It is not a stupid question but a very valid one. > > 2. I was aware of the EMI possibility and tried ferrites on the > supply and signal wires with no result. > > 3. I will try batteries but have to find enough of them. > > 4. On the spectrum analyzer, I checked the amplitude setting and > 10dB > change gave 10dB change of signal level. Also a mixer level change > had no influence on the spurious. > > Henk > > > On Apr 25, 2007, at 22:07, Poul-Henning Kamp wrote: > >> >> I'm going to ask a seemingly stupid question, but bear with me: >> >> Are you sure those signals are really present on the output ? >> >> The reason why I ask is that you are in a frequency territory where >> EMI is both radiated and conducted so you have to be really careful >> with your setup, grounding in particular, to make sure you do not >> actually measure the PRS10 acting as an antenna. >> >> The best way to ensure this, is to run your PRS10 off batteries, >> Sealed Lead Acid for instance, and the only other connection to >> the PRS10 should be the coax to the spectrum analyzer. >> >> Poul-Henning >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> [EMAIL PROTECTED] | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by >> incompetence. >> >> ___ >> time-nuts mailing list >> time-nuts@febo.com >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In message <[EMAIL PROTECTED]>, Henk ten Pi erick writes: >2. I was aware of the EMI possibility and tried ferrites on the >supply and signal wires with no result. If your powersupply is not very high quality, you are almost certain to create a ground-loop through the power-cords of the power-supply and the spectrum analyzer. That's why batteries are such a good thing: they don't offer a path for ground loops. If you have a isolating transformer, you can try that in the signal cable between the oscilloscope and the PRS10, but it's not as good as running off batteries. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/25/2007 12:49:47 Pacific Daylight Time, [EMAIL PROTECTED] writes: spurious. The spurious seem to be harmonics of the 357MHz synthesizer, we see the 1st, 2nd, 3rd and 4th harmonic. (The marker is on the 3rd harmonic). The spurious between 500MHz and 700MHz are not yet explained. Around 357MHz are sidebands at 290kHz distance. Does anyone have schematics? Hi Henk, if you can't fix the unit (seems it has much more spurs than my unit) then maybe a simple high-quality low ESR 100pF to ground after a 4.7 Ohm series resistor on the 10MHz output may reduce the high-frequency stuff a bit... bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Hi Poul-Henning, 1. It is not a stupid question but a very valid one. 2. I was aware of the EMI possibility and tried ferrites on the supply and signal wires with no result. 3. I will try batteries but have to find enough of them. 4. On the spectrum analyzer, I checked the amplitude setting and 10dB change gave 10dB change of signal level. Also a mixer level change had no influence on the spurious. Henk On Apr 25, 2007, at 22:07, Poul-Henning Kamp wrote: > > I'm going to ask a seemingly stupid question, but bear with me: > > Are you sure those signals are really present on the output ? > > The reason why I ask is that you are in a frequency territory where > EMI is both radiated and conducted so you have to be really careful > with your setup, grounding in particular, to make sure you do not > actually measure the PRS10 acting as an antenna. > > The best way to ensure this, is to run your PRS10 off batteries, > Sealed Lead Acid for instance, and the only other connection to > the PRS10 should be the coax to the spectrum analyzer. > > Poul-Henning > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [EMAIL PROTECTED] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by > incompetence. > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
I'm going to ask a seemingly stupid question, but bear with me: Are you sure those signals are really present on the output ? The reason why I ask is that you are in a frequency territory where EMI is both radiated and conducted so you have to be really careful with your setup, grounding in particular, to make sure you do not actually measure the PRS10 acting as an antenna. The best way to ensure this, is to run your PRS10 off batteries, Sealed Lead Acid for instance, and the only other connection to the PRS10 should be the coax to the spectrum analyzer. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Hi, Thank you all for the frequency plots of the PRS10. It is very interesting to see these and find the differences. In the mean time I have restarted my PRS10 and have seen that some spurious signals are large at start up and reduce after that. I have attached a screen shot of the hp8590 spectrum analyzer showing the spurious. The spurious seem to be harmonics of the 357MHz synthesizer, we see the 1st, 2nd, 3rd and 4th harmonic. (The marker is on the 3rd harmonic). The spurious between 500MHz and 700MHz are not yet explained. Around 357MHz are sidebands at 290kHz distance. Does anyone have schematics? Henk ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/25/2007 11:55:53 Pacific Daylight Time, [EMAIL PROTECTED] writes: >And on the opposite front, the TSC-5120 isn't very happy with a square >wave input, particularly if harmonics fall within its input range. The >symptom is lots of spurs showing up in the phase noise plots. Adding a >low pass filter with an appropriate cutoff helps a lot. Very true! Have seen these spurs on the 5210A as well. A sharp 13MHz or so cut-off filter will help that. bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
[EMAIL PROTECTED] wrote: > Also, try making the sine wave of the PRS10 into a nice, fast edge rate > square-wave with a Fairchild NC7SZ04 driver inverter for example. The > Wavecrest > units don't work as well with sine waves as with square waves. On the SZ04, > put > a 10nF cap in series to the input, and a 1 MEG resistor from it's input pin > to it's output pin. Feed the chip from a very low noise 5V power source. > Insert a 40-50 Ohm resistor into the output path going to the coax. Put an > attenuator/AC-coupler into the coax so the Wavecrest doesen't get overloaded > by > the 2.5Vpp DC signal. Result: low noise comparator/buffer :) And on the opposite front, the TSC-5120 isn't very happy with a square wave input, particularly if harmonics fall within its input range. The symptom is lots of spurs showing up in the phase noise plots. Adding a low pass filter with an appropriate cutoff helps a lot. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/24/2007 15:14:11 Pacific Daylight Time, [EMAIL PROTECTED] writes: >> It is unclear to me if the spurious is normal or not. The spurious of >> my PRS10 is 60dB down the 10MHz so it is strange that you see no >> spurious. >> Hi Henk, try running your PRS10 from a Pb battery, with nothing else connected (no RS232 etc). The plot I sent you was from a PRS running from a switching power supply, with RS-232 connected to some other stuff. Also, try making the sine wave of the PRS10 into a nice, fast edge rate square-wave with a Fairchild NC7SZ04 driver inverter for example. The Wavecrest units don't work as well with sine waves as with square waves. On the SZ04, put a 10nF cap in series to the input, and a 1 MEG resistor from it's input pin to it's output pin. Feed the chip from a very low noise 5V power source. Insert a 40-50 Ohm resistor into the output path going to the coax. Put an attenuator/AC-coupler into the coax so the Wavecrest doesen't get overloaded by the 2.5Vpp DC signal. Result: low noise comparator/buffer :) bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Brooke Clarke wrote: > Hi: > > Sorry. That was a phase plot in the same folder on my computer. > Here's my spectrum plot. > > Have Fun, > > Brooke > http://www.PRC68.com > http://www.pacificsites.com/~brooke/PRC68COM.shtml > http://www.precisionclock.com > > Brooke The 15MHz, 25MHz and 35MHz spurs are possibly produced by the internal microprocessor (400ns cycle time clocked at 10MHz). The lamp oscillator at around 150MHz may also contribute spurs. The synthesizer may also contribute spurs. It would have been nice if the lamp excitation oscillator was locked to the 10MHz crystal. The poor close in phase noise performance is probably due to the use of saturation as a limiting mechanism in the 10MHz crystal oscillator. Using cutoff would have been better, however varying the oscillator transistor collector voltage with a DAC to control the amplitude is convenient. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Hi: Sorry. That was a phase plot in the same folder on my computer. Here's my spectrum plot. Have Fun, Brooke http://www.PRC68.com http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Brooke Clarke wrote: Hi Henk: Here is a spectrum plot from my PRS10. But it's also connected to the SR620 so I'm not sure where the spurs are coming from. Have Fun, Brooke Clarke http://www.PRC68.com http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Henk ten Pierick wrote: Hi Said, Thanks for the picture. I have inserted a 100MHz lowpass between the PRS10 and the Wavecrest tot remove the spurious signals. There is a large difference in phase noise close to the carrier as calculated by the Wavecrest. It is unclear to me if the spurious is normal or not. The spurious of my PRS10 is 60dB down the 10MHz so it is strange that you see no spurious. Henk On Apr 24, 2007, at 20:18, [EMAIL PROTECTED] wrote: In a message dated 4/23/2007 10:51:38 Pacific Daylight Time, [EMAIL PROTECTED] writes: Your picture's input level is 5dBm. The SRS spec for PRS10 is 7dBm output. Were is the difference? Did you measure wideband spectrum of the PRS10 output? Up to 1GHz? retry: the attachement was too big first time I tried sending this: Hi Henk, I measured my PRS-10 tonight on an 8563E, you can see the output is +6dBm. There are a bunch of spurs up to 200MHz, nothing noteworthy above that, I checked to 1GHz. See the attachement. Some of these spurs don't look like they are harmonics, but it would take time to investigate all spurs. Hope this helps you, bye, Said ** See what's free at http:// www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts PRS10.pdf Description: Adobe PDF document ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Brooke Clarke wrote: > Hi Henk: > > Here is a spectrum plot from my PRS10. But it's also connected to the > SR620 so I'm not sure where the spurs are coming from. > > Have Fun, > > Brooke Clarke Brooke 60Hz spur - mains related? 70Hz spur from internal phase modulation frequency used in PRS10? Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Hi Henk: Here is a spectrum plot from my PRS10. But it's also connected to the SR620 so I'm not sure where the spurs are coming from. Have Fun, Brooke Clarke http://www.PRC68.com http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com Henk ten Pierick wrote: Hi Said, Thanks for the picture. I have inserted a 100MHz lowpass between the PRS10 and the Wavecrest tot remove the spurious signals. There is a large difference in phase noise close to the carrier as calculated by the Wavecrest. It is unclear to me if the spurious is normal or not. The spurious of my PRS10 is 60dB down the 10MHz so it is strange that you see no spurious. Henk On Apr 24, 2007, at 20:18, [EMAIL PROTECTED] wrote: In a message dated 4/23/2007 10:51:38 Pacific Daylight Time, [EMAIL PROTECTED] writes: Your picture's input level is 5dBm. The SRS spec for PRS10 is 7dBm output. Were is the difference? Did you measure wideband spectrum of the PRS10 output? Up to 1GHz? retry: the attachement was too big first time I tried sending this: Hi Henk, I measured my PRS-10 tonight on an 8563E, you can see the output is +6dBm. There are a bunch of spurs up to 200MHz, nothing noteworthy above that, I checked to 1GHz. See the attachement. Some of these spurs don't look like they are harmonics, but it would take time to investigate all spurs. Hope this helps you, bye, Said ** See what's free at http:// www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts PRS10_phase_noise.pdf Description: Adobe PDF document ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Hi Said, Thanks for the picture. I have inserted a 100MHz lowpass between the PRS10 and the Wavecrest tot remove the spurious signals. There is a large difference in phase noise close to the carrier as calculated by the Wavecrest. It is unclear to me if the spurious is normal or not. The spurious of my PRS10 is 60dB down the 10MHz so it is strange that you see no spurious. Henk <> On Apr 24, 2007, at 20:18, [EMAIL PROTECTED] wrote: In a message dated 4/23/2007 10:51:38 Pacific Daylight Time, [EMAIL PROTECTED] writes: Your picture's input level is 5dBm. The SRS spec for PRS10 is 7dBm output. Were is the difference? Did you measure wideband spectrum of the PRS10 output? Up to 1GHz? retry: the attachement was too big first time I tried sending this: Hi Henk, I measured my PRS-10 tonight on an 8563E, you can see the output is +6dBm. There are a bunch of spurs up to 200MHz, nothing noteworthy above that, I checked to 1GHz. See the attachement. Some of these spurs don't look like they are harmonics, but it would take time to investigate all spurs. Hope this helps you, bye, Said ** See what's free at http:// www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/23/2007 11:27:39 Pacific Daylight Time, [EMAIL PROTECTED] writes: >I will zip and send off list. Thanks!! > >> Do you have the Vectron OCXO specs? > > No, but someone on this list mentioned some time ago that they sold > these > units to Vectron (Bruce?) and posted some specs, I forgot who that was > unfortunately... >It is not clear to me if it is possible to measure the PRS10 10Hz >phase noise spec with the Wavecrest. >Any idea? I used a SIA-3000 in FFT mode for phase noise measurements, they really are not that great for that purpose. Don't think we can get down to -130dBc at 10Hz with accuracy. Then again one could measure loads of TI data on the DTS, and do an FFT on that data. > I had a third DTS unit for parts, and that unit's Vectron was out > of spec > (just shy of 100MHz at full mechanical deflection unfortunately). > Datecode 1994, > so not too bad. >So, if I need parts No prob :) I suspect that replacing the simple Vectron 100MHz OCXO with a more modern, lower noise Wenzel etc could improve the instruments performance. That OCXO should be locked to GPS as well of course :) bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
On Apr 23, 2007, at 20:13, [EMAIL PROTECTED] wrote: > >> Your nice picture shows a -95dBc phase noise at 10Hz. >> The SRS spec for PRS10 is -130dBc at 10Hz. Can you explain that >> difference of 35dBc? > > The X axis is labeled in exponential form by the TSC instrument, it's > actually -95dBc/Hz at 1Hz (10E0), and -130dBc/Hz at 10Hz (10E1) > just meeting the > SRS specifications I should have looked better >> Did you measure wideband spectrum of the PRS10 output? Up to 1GHz? > > Not yet, but I will try that tonight. > > >> BTW: do you have Visi for windows by any chance? > > An old evaluation version3 > > Can I get a copy for evaluation from you please? I bought version > 1.16, very > old and have been desperately trying to find a more modern version > that runs > on Win2K etc. I will zip and send off list. > >> Do you have the Vectron OCXO specs? > > No, but someone on this list mentioned some time ago that they sold > these > units to Vectron (Bruce?) and posted some specs, I forgot who that was > unfortunately... It is not clear to me if it is possible to measure the PRS10 10Hz phase noise spec with the Wavecrest. Any idea? > I had a third DTS unit for parts, and that unit's Vectron was out > of spec > (just shy of 100MHz at full mechanical deflection unfortunately). > Datecode 1994, > so not too bad. So, if I need parts Henk ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/23/2007 10:51:38 Pacific Daylight Time, [EMAIL PROTECTED] writes: Hi Henk, >The $900 unit on ebay was a DTS2070. >Yes, I have bought that unit for my home lab but it has not yet arrived. Same OCXO as the DTS2075... > Attached is a PRS-10 phase noise plot I measured here with a > TSC-5120A unit. > You can see pretty low spurs, but only a 100KHz measurement range. > One would > think to have a perfect oscillator until plugging in the PRS-10 > into the > Wavecrest... >Your nice picture shows a -95dBc phase noise at 10Hz. >The SRS spec for PRS10 is -130dBc at 10Hz. Can you explain that >difference of 35dBc? The X axis is labeled in exponential form by the TSC instrument, it's actually -95dBc/Hz at 1Hz (10E0), and -130dBc/Hz at 10Hz (10E1) just meeting the SRS specifications. >Your picture's input level is 5dBm. >The SRS spec for PRS10 is 7dBm output. Were is the difference? I think this falls almost within the range of the output of the PRS-10 (6 - 8dBm range), but I may have used a 1.5dB attenuator for better VSWR (don't remember), but for phase noise measurements I don't usually add attenuation. Also, I think that power number by the TSC-5120A is not very accurate itself (single digit resolution etc). >Did you measure wideband spectrum of the PRS10 output? Up to 1GHz? Not yet, but I will try that tonight. > BTW: do you have Visi for windows by any chance? An old evaluation version3 Can I get a copy for evaluation from you please? I bought version 1.16, very old and have been desperately trying to find a more modern version that runs on Win2K etc. > I have two DTS units, one with about 2.7ps jitter on the 100MHz > output > another with about 3ps. I wonder if replacing the internal Vectron > 100MHz OCXO > (which really is very low tech - I opened one and it actually uses > a CA3130 as > the oven controller :( ) would improve the unit's performance?? >Do you have the Vectron OCXO specs? No, but someone on this list mentioned some time ago that they sold these units to Vectron (Bruce?) and posted some specs, I forgot who that was unfortunately... I had a third DTS unit for parts, and that unit's Vectron was out of spec (just shy of 100MHz at full mechanical deflection unfortunately). Datecode 1994, so not too bad. Bye, Said Henk ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
On Apr 22, 2007, at 23:47, [EMAIL PROTECTED] wrote: > Hi Henk, > > great to hear that you got a Wavecrest DTS-2075!! That machine can > detect > spurs that phase noise measurements are oblivious too. Spurs cause > nasty > deterministic jitter of course. That DTS2075 is at my employers lab. > That must have been the unit for sale on Ebay for > $900? The $900 unit on ebay was a DTS2070. Yes, I have bought that unit for my home lab but it has not yet arrived. > Attached is a PRS-10 phase noise plot I measured here with a > TSC-5120A unit. > You can see pretty low spurs, but only a 100KHz measurement range. > One would > think to have a perfect oscillator until plugging in the PRS-10 > into the > Wavecrest... Your nice picture shows a -95dBc phase noise at 10Hz. The SRS spec for PRS10 is -130dBc at 10Hz. Can you explain that difference of 35dBc? Your picture's input level is 5dBm. The SRS spec for PRS10 is 7dBm output. Were is the difference? Did you measure wideband spectrum of the PRS10 output? Up to 1GHz? > BTW: do you have Visi for windows by any chance? An old evaluation version3 > I have two DTS units, one with about 2.7ps jitter on the 100MHz > output > another with about 3ps. I wonder if replacing the internal Vectron > 100MHz OCXO > (which really is very low tech - I opened one and it actually uses > a CA3130 as > the oven controller :( ) would improve the unit's performance?? Do you have the Vectron OCXO specs? Henk ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/22/2007 15:55:37 Pacific Daylight Time, [EMAIL PROTECTED] writes: >Causes >Resonance in bypass/filter/coupling network coupled with slight non >linearity in an amplifier or AGC detector diode? >Bruce Hi Bruce, yeah sounds probable, I wonder why Wenzel and SRS don't use low pass filters though since these spurs can intermodulate with circuitry using the 10MHz... bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Said [EMAIL PROTECTED] wrote: > Spurs cause nasty deterministic jitter of course. Only if the spurs are not harmonics. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Said [EMAIL PROTECTED] wrote: > > Hi Henk, > > I have a expensive 10MHz ultra-low-noise Wenzel oscillator that we bought > some months ago that has similar very nasty noise on it's output. > > See the attached HP8563E plot, you can see the worst spur at 280MHz at > -56dBm, which is about -50dBc/Hz! > > The Wenzel has a measured phase noise floor of -169dBc/Hz at 10Khz. > > In comparison, see our Jackson-Labs Fury GPSDO output measured exactly the > same way - one can only see the second and third harmonic everything else is > killed by the seventh-order low pass filter. > > I asked Wenzel about this noise, and they said "we see it too, it's caused > by the HP8563E spectrum analyzer itself, we are not worried about it". > > Well, Wenzel went silent when I sent them the attached plots of an MTI-230 > OCXO raw output, and our Fury GPSDO output both measured on the same 8563E > setup. Never heard from them since. > > I think the measurements show that it's pretty important to put a low pass > filter on the output of OCXO's. > > I wonder what is generating such high frequency, high energy spurs in these > OCXO's. > > bye, > Said > > Actually a bandpass filter is even better, particularly for higher frequency OCXOs, but don't get too aggressive in lowering the bandwidth or the phase instabilities of the filter will degrade the performance. Rather a combination of a low pass and a high pass filter with reasonbly wide bandpass so that the effect of minor component instabilities only have a small effect on the phase of the desired OCXO output frequency. If there are any spurious output frequencies relatively close to the deired frequency then a bandstop filter tuned to the unwanted frequency has better phase stability at the desired frequency than anarrow band bandpass filter tuned to the desired output frequency. For the ultimate in phase stability avoid ferrite core inductors, air core or powdered iron core inductors have lower (close in) phase noise. Causes Resonance in bypass/filter/coupling network coupled with slight non linearity in an amplifier or AGC detector diode? Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
In a message dated 4/22/2007 12:55:08 Pacific Daylight Time, [EMAIL PROTECTED] writes: >John, >The PRS10 has a phase noise spec of -130dBc at 10Hz distance. The >only way for me to measure this is with a Wavecrest 2075 and the >PRS10 was not a expected. It was not better than my R&S SMX. Trying >to find out why I found the spurious which also are seen by the >Wavecrest. I will filter the spurious out of coarse and re-measure >but are at least surprised to find this frequency spectrum. >I know that there are more PRS10 owners with the time-nuts, I expect >them to be phase-noise-nuts as well. Henk Hi Henk, great to hear that you got a Wavecrest DTS-2075!! That machine can detect spurs that phase noise measurements are oblivious too. Spurs cause nasty deterministic jitter of course. That must have been the unit for sale on Ebay for $900? Attached is a PRS-10 phase noise plot I measured here with a TSC-5120A unit. You can see pretty low spurs, but only a 100KHz measurement range. One would think to have a perfect oscillator until plugging in the PRS-10 into the Wavecrest... BTW: do you have Visi for windows by any chance? I have two DTS units, one with about 2.7ps jitter on the 100MHz output another with about 3ps. I wonder if replacing the internal Vectron 100MHz OCXO (which really is very low tech - I opened one and it actually uses a CA3130 as the oven controller :( ) would improve the unit's performance?? thanks, bye, Said ** See what's free at http://www.aol.com. PRS10_phase_noise.pdf Description: Adobe PDF document ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
John, The PRS10 has a phase noise spec of -130dBc at 10Hz distance. The only way for me to measure this is with a Wavecrest 2075 and the PRS10 was not a expected. It was not better than my R&S SMX. Trying to find out why I found the spurious which also are seen by the Wavecrest. I will filter the spurious out of coarse and re-measure but are at least surprised to find this frequency spectrum. I know that there are more PRS10 owners with the time-nuts, I expect them to be phase-noise-nuts as well. Henk On Apr 22, 2007, at 20:47, John Ackermann N8UR wrote: > Henk, I don't know particulars about the PRS10, but spurs anywhere > that > are 60dB down are probably not a problem; check the docs and I'll bet > that non-harmonic spurs are only spec'd at maybe 40dB down (and I'd > argue that the 58th harmonic no longer counts as a harmonic; the > harmonics they're talking about are low order). > > John > > > Henk ten Pierick said the following on 04/22/2007 02:28 PM: >> Hello, >> >> Sorry for the reply, hit the wrong button. But: >> >> The output spectrum of my just bought PRS10 has spurious frequencies >> from 580MHz in steps of 10MHz up to 680MHz. The 580MHz and 680MHz >> signals just above the noise. The 630MHz amplitude 60dB down the >> 10MHz. Does anyone know if this a normal output? >> >> Henk >> >> >> >> ___ >> time-nuts mailing list >> time-nuts@febo.com >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >> > > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] retry: PRS10 has spurious frequencies
Henk, I don't know particulars about the PRS10, but spurs anywhere that are 60dB down are probably not a problem; check the docs and I'll bet that non-harmonic spurs are only spec'd at maybe 40dB down (and I'd argue that the 58th harmonic no longer counts as a harmonic; the harmonics they're talking about are low order). John Henk ten Pierick said the following on 04/22/2007 02:28 PM: > Hello, > > Sorry for the reply, hit the wrong button. But: > > The output spectrum of my just bought PRS10 has spurious frequencies > from 580MHz in steps of 10MHz up to 680MHz. The 580MHz and 680MHz > signals just above the noise. The 630MHz amplitude 60dB down the > 10MHz. Does anyone know if this a normal output? > > Henk > > > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] retry: PRS10 has spurious frequencies
Hello, Sorry for the reply, hit the wrong button. But: The output spectrum of my just bought PRS10 has spurious frequencies from 580MHz in steps of 10MHz up to 680MHz. The 580MHz and 680MHz signals just above the noise. The 630MHz amplitude 60dB down the 10MHz. Does anyone know if this a normal output? Henk ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
