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I wonder if anyone here has experience or access to an Agilent E5052A signal source analyser? Mine is about 20 years old and is recently showing signs of unreliability.
The main symptom is an occasional power on self test fail and it then reports issues with a 3V3 power supply voltage on the A3 DSP/ADC board where it reads low at typically 2.96V. I think a pass requires >2.96V but this may be firmware dependent. My E5052A is running the latest firmware V2.51.
I think this 3V3 supply is common across the backplane but it gets reported as an A3 test in the service menu. The 5V PSU rail also reads low at between 4.7 and 4.8V but this is still a pass (shows true for the test result)
Also, for several years now it has shown a stubborn internal spurious at 60 kHz at a very low level. This very slightly spoils any phase noise measurements even though it shows up at about -140dBc then the trace is in phase noise mode in dBc/Hz. I'm not sure what causes this internal 60 kHz term, it may be from a PSU or the display or a divided clock. It may be that the 60kHz spurious term is a feature of this analyser as it is present on all my plots dating back over 13 years. It's not caused by anything nearby to the instrument as it does it regardless of position or proximity to other equipment. Plus the other E5052A I've used in the past (in a different location) is exactly the same.
The 60kHz spurious is also present when I swap across to the baseband input even with a very clean LF signal fed to the 0-40 MHz baseband input. So this spurious must be getting in at the ADC if it affects the baseband input as well.
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I've seen similar on another E5052A that also shows a lowish 3V3 voltage (but it never shows a power on test failure) and it also has the permanent 60 kHz spurious on all phase noise tests on the main RF input.
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The service menu password is only three characters long and is 'kid'
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If anyone has access to a healthy E5052A could they enter the service menu and do a manual Power On Test (POT) in the service menus? Then report the 5V and 3.3V results for the A3 module
Mine shows anything from 2.91V to 3.05V and I think the pass/fail threshold for the POT is somewhere around 2.96V. The other E5052A I have some access to shows 2.982V to 3.08V and never reports a POT failure.
Thanks in advance for any replies
Jeremy
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Hi, Jeremy. ?Let me take a look around the labs here at Raytheon. ?Might be an E5052A or two that I could fire up. ?Give me a couple hours.
Jim Ford? Laguna Hills, California, USA
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On Feb 24, 2025, at 10:17?AM, jmr via groups.io <jmrhzu@...> wrote:
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I wonder if anyone here has experience or access to an Agilent E5052A signal source analyser? Mine is about 20 years old and is recently showing signs of unreliability.
The main symptom is an occasional power on self test fail and it then reports issues with a 3V3 power supply voltage on the A3 DSP/ADC board where it reads low at typically 2.96V. I think a pass requires >2.96V but this may be firmware dependent. My E5052A is running the latest firmware V2.51.
I think this 3V3 supply is common across the backplane but it gets reported as an A3 test in the service menu. The 5V PSU rail also reads low at between 4.7 and 4.8V but this is still a pass (shows true for the test result)
Also, for several years now it has shown a stubborn internal spurious at 60 kHz at a very low level. This very slightly spoils any phase noise measurements even though it shows up at about -140dBc then the trace is in phase noise mode in dBc/Hz. I'm not sure what causes this internal 60 kHz term, it may be from a PSU or the display or a divided clock. It may be that the 60kHz spurious term is a feature of this analyser as it is present on all my plots dating back over 13 years. It's not caused by anything nearby to the instrument as it does it regardless of position or proximity to other equipment. Plus the other E5052A I've used in the past (in a different location) is exactly the same.
The 60kHz spurious is also present when I swap across to the baseband input even with a very clean LF signal fed to the 0-40 MHz baseband input. So this spurious must be getting in at the ADC if it affects the baseband input as well.
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I've seen similar on another E5052A that also shows a lowish 3V3 voltage (but it never shows a power on test failure) and it also has the permanent 60 kHz spurious on all phase noise tests on the main RF input.
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The service menu password is only three characters long and is 'kid'
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If anyone has access to a healthy E5052A could they enter the service menu and do a manual Power On Test (POT) in the service menus? Then report the 5V and 3.3V results for the A3 module
Mine shows anything from 2.91V to 3.05V and I think the pass/fail threshold for the POT is somewhere around 2.96V. The other E5052A I have some access to shows 2.982V to 3.08V and never reports a POT failure.
Thanks in advance for any replies
Jeremy
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Hi Jim, thanks.
I've just spent some time fishing around the outside of the chassis with a loop probe and the 60 kHz spurious is from the front of the instrument around the display. It isn't a single tone, it is spread over many kHz on the high side of 60 kHz and looks to be caused by digital traffic. It might be the display causing it. It seems to be at 59 kHz and it may be backlight related but it looks like it has some digital traffic on it.?
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Probing around the screen area of an E5071B VNA (I think this has the same touch screen display) shows exactly the same waveform so it is definitely screen related in some way. I'm not sure how this is getting into the baseband path but because it is also there on the main phase noise display I think it is getting in at the ADC/DSP module, possibly via a power supply rail. Hopefully a tired decoupling cap is the cause.
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Turning the backlight off makes the spurious term go away when probing :)
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There is a soft menu button that turns off the backlight and pressing this makes the spurious vanish on the probe (that feeds to another spectrum analyser).
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Also if I do a screen grab via Excel and GPIB (with the backlight ON) the 60kHz spurious is present on the spectrum from the baseband input. But if I grab the screen with the backlight off the baseband spectrum is clean on the grabbed screen image in Excel. A huge improvement.
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I guess I can live with this when grabbing screen plots as (hopefully) I can add the 'backlight off' command to the excel routine.
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So screen grabs will look much better. I'll have a look for the backlight command in the programming guide...
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Sounds about right. ?60 kHz is right in the range of a switching regulator of that era.
I didn’t find a signal source analyzer around the particular lab I frequent, but I’d be very surprised if there weren’t one somewhere in this building. ?Literally tons of vintage test equipment lying around here, much of it from the old Hughes Aircraft days. ?Glad you at least figured out where the spur was coming from.
Jim
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On Feb 24, 2025, at 12:53?PM, jmr via groups.io <jmrhzu@...> wrote:
? Turning the backlight off makes the spurious term go away when probing :)
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There is a soft menu button that turns off the backlight and pressing this makes the spurious vanish on the probe (that feeds to another spectrum analyser).
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Also if I do a screen grab via Excel and GPIB (with the backlight ON) the 60kHz spurious is present on the spectrum from the baseband input. But if I grab the screen with the backlight off the baseband spectrum is clean on the grabbed screen image in Excel. A huge improvement.
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I guess I can live with this when grabbing screen plots as (hopefully) I can add the 'backlight off' command to the excel routine.
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So screen grabs will look much better. I'll have a look for the backlight command in the programming guide...
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These SSAs are fairly rare items as they weren't produced in high qty by Agilent and they were quite expensive when new. I think they were $80k to $90k new. So you might not find one even in a large and well equipped lab.
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I'm probably going to take the ATX power supply apart and check the electrolytic caps in it. There may also be some tired connections inside. The average power consumption is about 220W which probably puts quite a strain on the ATX PSU over a two decade timespan.
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It's all OK now, I took it apart and fixed it :) :) :)
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On the DSP/ADC module A3 the 5V rail is now 4.97V (was 4.70V typical) and the 3V3 rail is now 3.24V (was 2.97V and very drifty).
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I disassembled the main firmware and worked out how it does the power on testing of the power supplies and this gave me the pass/fail limits for all the supplies.?
I was able to trace through the power supply distribution and see where it was losing voltage in a poor connection. A thermal camera helped a lot here. It's now all fixed and fine again!
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I also found out a few things about how it manages the internal 10 MHz reference and how to adjust the high stability 10 MHz OCXO. So that is now calibrated.
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I am so pleased, I thought it was slowly dying on me. There's no way I could afford to send it to Keysight for repair.
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I should be able to fix the other E5052A as well as it has a similar issue with a sagging 5V and a sagging 3V3 supply.
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Great!? That's the best kind of repair; when you learn something in addition to getting it working again.
Jim Ford Laguna Hills, California, USA
On Saturday, March 1, 2025 at 05:43:25 AM CST, jmr via groups.io <jmrhzu@...> wrote:
It's all OK now, I took it apart and fixed it :) :) :)
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On the DSP/ADC module A3 the 5V rail is now 4.97V (was 4.70V typical) and the 3V3 rail is now 3.24V (was 2.97V and very drifty).
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I disassembled the main firmware and worked out how it does the power on testing of the power supplies and this gave me the pass/fail limits for all the supplies.?
I was able to trace through the power supply distribution and see where it was losing voltage in a poor connection. A thermal camera helped a lot here. It's now all fixed and fine again!
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I also found out a few things about how it manages the internal 10 MHz reference and how to adjust the high stability 10 MHz OCXO. So that is now calibrated.
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I am so pleased, I thought it was slowly dying on me. There's no way I could afford to send it to Keysight for repair.
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I should be able to fix the other E5052A as well as it has a similar issue with a sagging 5V and a sagging 3V3 supply.
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Hi Jeremy,
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This is a great win. What is your overall impression of the E5052A?
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I have R& FSPN8 and 53100A but I would like something I can try to push to lower phase noise levels. I need below -120dBc/Hz at 1Hz and below -180 far out.
FSPN8 gets there but very slowly as its references are not ultra low noise level class. And it does not allow to use external references like 53100A or 5052A.
53100A is OK but has some spurs I can't get rid of and I also like all-in-one instruments.
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If you were to stick ULN Wenzels or comparable references on 5052A would you reliably get below -120dB @ 1Hz and -180 far out?
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Thanks
Leo
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Hi Leo
This E5052A is quite old now and it does have a few internal spurious terms. Also the noise floor performance isn't that great even down at 10 MHz.
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I don't have any oscillators here that can generate really low phase noise close to carrier. A few years ago I designed a 10 MHz crystal oscillator with low phase noise but I think it only managed a noise floor of about -173dBc/Hz from 10 kHz onwards. This was the theoretical noise floor of the oscillator (at least according to my basic calculations) but I don't think I've ever seen -180dBc/Hz even with lots of correlation. I've never used more that 100 for the correlation setting though.
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I'm fairly certain the E5052A just uses an external reference to discipline the internal reference. Both of the E5052A analysers that I have used have an internal high stability OCXO mounted inside the chassis and this has its own output at the rear panel. The idea is to link it to the REF IN connector with a short BNC-BNC jumper and then it shows up as an external reference even though it is actually inside the chassis. My E5071B VNA uses a similar system for the OCXO option.
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If this BNC-BNC link is removed then the E5052A uses the main 10 MHz oscillator inside and the OCXO is ignored.
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The best thing about the E5052A is that it is very fast. What isn't so good is the qty of internal spurious terms, especially the one from the backlight at 60 kHz. I don't think it can compete with modern alternatives in terms of the noise floor it can achieve. The E5052B is going to be better I think. Hopefully the internal spurious are improved on the E5052B as well.
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The baseband input of the E5052A is normally locked out in software with no mention in the documents how to unlock it. I think Agilent decided to hide this feature, probably because of the internal spurious that spoil the performance and also the noise floor rises a fair bit at low frequencies. There is also an enhanced jitter option which I've played with but I don't have much need for stuff like that. The jitter option is documented and available but the baseband isn't. I had to hack inside the firmware of this E5052A to find out how to release the baseband option. It can't be done via the option menus in the way the jitter option can be unlocked.
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If you look on Eevblog, I'm currently testing one of your LBE-1421 GPSDOs.? I'm getting the same result for phase noise that you did. I'm G0HZU on Eevblog.
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Regards
Jeremy
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-120dBc/Hz at 1 Hz is way better than anything I've experienced. I had a look at a plot of my homebrew oscillator and it managed -116dBc/Hz at 10 Hz.? Pretty lame by comparison...
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I guess you are aware of the Jeremy Everard paper from the University of York. This describes a 10 MHz ultra low noise oscillator that achieves -122dBc/Hz at 1 Hz offset.
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They used a Symmetricom 5120A as below. Very impressive! I don't think the E5052A can get anywhere near this level of performance.
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I don't know if this helps, but I dug out the most recent Keysight calibration certificate for this E5052A and there is a noise floor test done at 70 MHz with correlation set to 1.
I'm not sure what is involved with this test or at what power level it is run at but the numbers for the noise floor seem to be very good! I don't have anything here that can replicate this test although I could probably design a low noise LC oscillator that could get close at a 1 MHz offset.
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I generally design wideband single loop synthesisers up at VHF through UHF and the E5052A is easily good enough for stuff like this.
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Watching this subject with interest.? Leo, you may want to check out OEWaves, Synergy Microwave, and Holzworth Instrumentation (now part of Maury Microwave) for ultralow PN sources and Rohde & Schwarz, OEWaves and Holzworth for measurement instruments.? Also, there are several source mfrs making sapphire resonant cavity oscillators.? You probably already know about these companies, but throwing the names out there just in case. Microchip (was Microsemi, was Symmetricomm, was Ball Efratom; correct me if I got that progression wrong) as well.
I bought one of your GPSDO models a few years ago; it's great!? Looking forward to getting one (or more) of your pulsers at some point.
I'm working on a synthesizer myself based on a long spool of optical fiber to get the ultralow phase noise.? The tradeoff is sidemodes, which are spurs in the microwave output.? I have an idea for a way to knock those down.? My goal is a low SWaP-C synth mainframe in a 3 rack unit box that can be expanded from 1 to 8 outputs DC to 18 GHz or so.? I just don't have the room for multiple 4 RU boxes (HPAK 8340, 8662, etc.)? Stay tuned!
Jim Ford Laguna Hills, California, USA
On Sunday, March 2, 2025 at 06:41:24 AM CST, jmr via groups.io <jmrhzu@...> wrote:
I don't know if this helps, but I dug out the most recent Keysight calibration certificate for this E5052A and there is a noise floor test done at 70 MHz with correlation set to 1.
I'm not sure what is involved with this test or at what power level it is run at but the numbers for the noise floor seem to be very good! I don't have anything here that can replicate this test although I could probably design a low noise LC oscillator that could get close at a 1 MHz offset.
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I generally design wideband single loop synthesisers up at VHF through UHF and the E5052A is easily good enough for stuff like this.
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Hi Jim, thanks. I obtained the cal certificate for the other E5052A today. It was calibrated less than a year ago and this one shows an even lower noise floor.? It's a slightly newer unit and it has some hardware changes although I'm not sure if these changes are the reason it is slightly cleaner than my E5052A. The service manual shows the hardware changes wrt serial number. It also has the same internal spurious frequencies as mine and they appear to be a bit higher in level. It has the backlight spurious at 60 kHz as well.
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Looking in the service manual, it appears to describe this test at 70 MHz where a (low phase noise) PSG sig gen is used as the signal source at 70 MHz and it is passed through a 10 kHz wide BPF. Presumably some form of crystal filter? This will then shave off all noise down to the thermal level in the stopbands of the filter.
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I tried this with my E5052A using a lower test frequency (10.7 MHz) and a 15 kHz wide crystal filter and I saw about -175 dBc/Hz at offsets above 1 MHz. Not as good as the newer E5052A but the cal certificate did quote an uncertainty of about +/- 4dB for this test type. I really should do the test at 70 MHz as well. The noise floor may be degraded for carrier frequencies as low as 10.7 MHz.
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70 MHz Surface Acoustic Wave (SAW) BPFs used to be common for satcom. ?10 kHz is very narrow, though.
I’m snickering a bit at the differences in spur performance in sig gens because I’ve seen exactly that issue before not too long ago. ?In my case it was a Keysight E8257D PSG that showed spurs >-60 dBc at around 1 kHz offset. ?Our project had about a 6 month lull, and when we got back to the lab and set up the benches again, no such spurs could be found! ?I figured the original spur was from a switching regulator, but who knows? ?Either that particular generator had a problem and we have been using a different one since then, or KS fixed that when it went for calibration. ?Cue the Twilight Zone theme!
Jim
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On Mar 3, 2025, at 11:46?AM, jmr via groups.io <jmrhzu@...> wrote:
? Hi Jim, thanks. I obtained the cal certificate for the other E5052A today. It was calibrated less than a year ago and this one shows an even lower noise floor.? It's a slightly newer unit and it has some hardware changes although I'm not sure if these changes are the reason it is slightly cleaner than my E5052A. The service manual shows the hardware changes wrt serial number. It also has the same internal spurious frequencies as mine and they appear to be a bit higher in level. It has the backlight spurious at 60 kHz as well.
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Looking in the service manual, it appears to describe this test at 70 MHz where a (low phase noise) PSG sig gen is used as the signal source at 70 MHz and it is passed through a 10 kHz wide BPF. Presumably some form of crystal filter? This will then shave off all noise down to the thermal level in the stopbands of the filter.
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I tried this with my E5052A using a lower test frequency (10.7 MHz) and a 15 kHz wide crystal filter and I saw about -175 dBc/Hz at offsets above 1 MHz. Not as good as the newer E5052A but the cal certificate did quote an uncertainty of about +/- 4dB for this test type. I really should do the test at 70 MHz as well. The noise floor may be degraded for carrier frequencies as low as 10.7 MHz.
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Unlikely to have been from a switching reg -- 1kHz is pretty low. Close-in spurs are often suppressed by some form of cancellation, and a little drift can cause the reappearance of spurs at around that level (or more). That's where I'd look first, anyway. But if it's gone, be happy (unless or until it comes back). :)
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 3/3/2025 1:42 PM, Jim Ford via groups.io wrote: In my case it was a Keysight E8257D PSG that showed spurs >-60 dBc at around 1 kHz offset. ?Our project had about a 6 month lull, and when we got back to the lab and set up the benches again, no such spurs could be found! ?I figured the original spur was from a switching regulator, but who knows?
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Thank you Jeremy,
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I might pick one up to play with.
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I have spoken to Jeremy Everard last year about shared low phase oscillators development and ended up sending him the actives I was using that they were going to test at the department.
He was using fully kitted out FSWP26 at the time but it was not perfect for low phase noise work.
To be honest far out noise between -170 and -180 is not a problem since cross-correlation gets it cleaned ?up within a minute or two.
It's the close in at 1Hz which takes forever to stabilise — I usually have to wait 30-40 minutes for it to reach -120dBc/Hz at 1Hz for 10MHz carrier.
Also 10-100Hz is a very problematic area where a lot of hash is holding cross-correlation stubbornly high for longer.
Leo
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On Sun, Mar 2, 2025 at 10:56 AM, jmr wrote:
The best thing about the E5052A is that it is very fast. What isn't so good is the qty of internal spurious terms, especially the one from the backlight at 60 kHz. I don't think it can compete with modern alternatives in terms of the noise floor it can achieve. The E5052B is going to be better I think. Hopefully the internal spurious are improved on the E5052B as well.
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Thanks, Jim!
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We have gone through all the usual suspects when choosing the phase noise kit for this round. There was also NoiseXT (is it former Aeroflex?)
Cross-correlation is a great advantage but you have to start with decent phase noise LOs if you want to keep the R&D cycle sensible.
I have no idea how people design long term high stability oscillators in one lifetime!
Leo
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On Sun, Mar 2, 2025 at 09:51 PM, Jim Ford wrote:
Watching this subject with interest.? Leo, you may want to check out OEWaves, Synergy Microwave, and Holzworth Instrumentation (now part of Maury Microwave) for ultralow PN sources and Rohde & Schwarz, OEWaves and Holzworth for measurement instruments.? Also, there are several source mfrs making sapphire resonant cavity oscillators.? You probably already know about these companies, but throwing the names out there just in case. Microchip (was Microsemi, was Symmetricomm, was Ball Efratom; correct me if I got that progression wrong) as well.
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I bought one of your GPSDO models a few years ago; it's great!? Looking forward to getting one (or more) of your pulsers at some point.
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I'm working on a synthesizer myself based on a long spool of optical fiber to get the ultralow phase noise.? The tradeoff is sidemodes, which are spurs in the microwave output.? I have an idea for a way to knock those down.? My goal is a low SWaP-C synth mainframe in a 3 rack unit box that can be expanded from 1 to 8 outputs DC to 18 GHz or so.? I just don't have the room for multiple 4 RU boxes (HPAK 8340, 8662, etc.)? Stay tuned!
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Jim Ford
Laguna Hills, California, USA
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Isn’t one solution to side modes using multiple (fiber) loops of different lengths, such that fewer frequencies fit?
(Borrowed thinking in terms of laser resonators and etalons where sometimes specific choices are made that permit only a single mode within the gain bandwidth of the amplifying media)
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Hi Leo.
I dug out my old homebrew 10 MHz xtal oscillator and measured it with the E5052A. One of the design goals for this was to be able to use it as a low noise LO for the E5052A so I could measure phase noise for carrier signals below 10 MHz.. But it was also an exercise to see if it agreed with theory and how low I could get the noise floor.
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The circuit does run the crystal with a very high drive level and I didn't bother trimming it to 10 MHz.?
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I used a basic MMIC gain block as the active device so I think I could improve on the close in noise by several dB if I used a lower noise device. I might revisit this at some point although the performance below is already good enough for my needs with the E5052A.
Regards
Jeremy
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