[time-nuts] 53132A Cooling fan
Hi, My 53132A cooling fan is becoming extremely noisy so I have to fix it or find ear plugs fast. If anybody as encountered the same problem witch I suppose is common I will be interested if there is replacement part easily available for that purpose. Regards Loïc ___ 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] 53132A Cooling fan
Following your comments, i have opened the enclosure, disconnected the power supply and measured the fan current ( 40mA) when connected to AC line. Ordered a 4020 model 12V with the proper current, seems very common My 53132A will be back on stage very soon Thanks for your help. Regards Loïc -Message d'origine- De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Bob Camp Envoyé : dimanche 11 janvier 2015 15:22 À : Discussion of precise time and frequency measurement Objet : Re: [time-nuts] 53132A Cooling fan Hi A very normal “spiral of death” on the 53132 is the fan going out and the power supply following it a month or two later. The supply apparently does need the fan cooling to keep it happy. Since the fan runs whenever the counter is plugged in, the fan logs a lot of hours. If you do loose the power supply, the one in the 53181 will swap over to the 132. It’s not a cheap fix, but better than scrapping a 132. Bob On Jan 11, 2015, at 12:59 AM, Loïc Moreau loic.mor...@eai.fr wrote: Hi, My 53132A cooling fan is becoming extremely noisy so I have to fix it or find ear plugs fast. If anybody as encountered the same problem witch I suppose is common I will be interested if there is replacement part easily available for that purpose. Regards Loïc ___ 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] LNA and Alias
Hi, I have just found the culprit The AD7760 eval board in charge of the ADC task, is equipped with a little 40 MHz clock witch seems to generate a beat note with my 10Mhz noise measurements setup. I have discovered the origin of the problem after disconnecting the LNA from the measurement chain and visualizing the output of the LNA with a scope. The beat note was clearly visible, 10mV peak-peak . After shutting down every 10Mhz sources in my lab (a huge task) and altering the frequency of my phase noise measurement setup noise floor, I noticed that the low frequency noise was in fact a beat note following the ref frequency adjustments. ( The ref OCXO was replaced with a 33521A to alter amplitude and frequency at will) . As soon as I fire up the 7.5V power supply of the eval AD7760 (the eval card is not connected to anything). the LNA give a steady 10mV beat note as the 40 MHz clock seems mixing up somewhere a few herz apart from the regular source, polluting the close in phase noise measurements . So after weeks of questioning, I was a bit disappointed to find out that the AD eval board, the least suspected item was at the origin of the problem. Now, I have to address it . I have noticed the presence of smb connectors on the eval card, so I may substitute the internal clock, and a shield enclosure may cure that little beast. At last DC power supply wires may also be substituted by shielded cable just in case. I am relieved Regards. Loïc -Message d'origine- De : time-nuts [mailto:time-nuts-boun...@febo.com] De la part de Bruce Griffiths Envoyé : lundi 22 décembre 2014 20:30 À : Discussion of precise time and frequency measurement Objet : Re: [time-nuts] LNA and Alias On Monday, December 22, 2014 09:26:15 AM Loïc wrote: Bruce Griffiths bruce.griffiths@... writes: Are you sure that the setup is aligned to minimise AM response? Are you using cross-correlation? Bruce On Monday, 22 December 2014 5:08 PM, Loïc Moreau loic.moreau at eai..fr wrote: Hi all, My phase noise measurements system give erroneous results in close in phase noise measurements, I got humps in the 1Hz-1000Hz area as high à 20 dB more than expected. The setup is using a mixer to compare reference and DUT witch drive an LNA http://www.ko4bb.com/~bruce/LowNoiseMixerPreamp.html , the output is driving an AD7760 ADC and an op amp circuity is connected to the VFC reference to achieve quadrature. The results are analyzed with an homebrew FFT charting software After struggling with different configurations, switched different LNA, ADC , sound card. A scope connected to the LNA output indicate steady 20MHz residuals just before the ADC ( around 10 mv peak-peak). In fact , it seems that the mixer 20Mhz residuals ( DUT + REF ) are entering the ADC and so theses alias give erroneous results in the 1Hz-100Hz area, displaying unexpected artifacts. In order to fix the problem I will probably include an analog filter just before the ADC input (same as LNA input 1nF 80µH), but I want to know if some more sophisticated measures should be undertaken as an 5th Order Lowpass Filter. I have not found many clue about alias problems in phase noise measurements literature so I may have missed something ? Any advice Loïc ___ time-nuts mailing list -- time-nuts@... To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time- nuts and follow the instructions there. Hi, I have a simple setup to measure the noise floor, the mixer is a SYM-2 and a divider is feeding RF and LO inputs ports for that purpose. a pi network give the 90° phase difference. Have you measured the phase shift when connected to the mixer? I usually use a narrowband 90 degree hybrid. The test is running with an HP 10811 giving around 7dBm, but i have the same results with any sources, especially a 33521A witch can be adjusted in level and frequency. I intend to use cross-correlation later when i will be confident with my the setup, for now i run a simple FFT. I have no clue about AM noise problem, i suppose that a sufficient input level on LO will put that problem aside. The phase shift between the RF and LO ports needs to be adjusted to minimise the response to AM in the source. To do this an AM modulator with low incidental PM is required. The phase is adjusted to minimise the sideband amplitude in the mixer output. by the way, I was a bit surprised that nobody pay any attention to RF leakage from multiplier as the low frequency level is order or magnitude lower than 20Mhz product present at the input. Sufficient attenuation is usually achieved by using a well balanced mixer and by the mixer IF port termination and the low pass filter network between the mixer IF port and the low noise preamp
[time-nuts] LNA and Alias
Hi all, My phase noise measurements system give erroneous results in close in phase noise measurements, I got humps in the 1Hz-1000Hz area as high à 20 dB more than expected. The setup is using a mixer to compare reference and DUT witch drive an LNA http://www.ko4bb.com/~bruce/LowNoiseMixerPreamp.html , the output is driving an AD7760 ADC and an op amp circuity is connected to the VFC reference to achieve quadrature. The results are analyzed with an homebrew FFT charting software After struggling with different configurations, switched different LNA, ADC , sound card. A scope connected to the LNA output indicate steady 20MHz residuals just before the ADC ( around 10 mv peak-peak). In fact , it seems that the mixer 20Mhz residuals ( DUT + REF ) are entering the ADC and so theses alias give erroneous results in the 1Hz-100Hz area, displaying unexpected artifacts. In order to fix the problem I will probably include an analog filter just before the ADC input (same as LNA input 1nF 80µH), but I want to know if some more sophisticated measures should be undertaken as an 5th Order Lowpass Filter. I have not found many clue about alias problems in phase noise measurements literature so I may have missed something ? Any advice Loïc ___ 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] Close in frequency stability
Hi, Here attached is a TBOLT screen shot, I am unable to go an ADEV @ 1s not better than 10-8 with timelab when I am measuring a 10-134 10 MHz source, I suppose that it is due to the short term stability of my TBOLT around 20 ppt rms with spikes coming up to 80 ppt . Putting directly the output of my external 10MHz ref in the input of my 53132A counter give some variation of the 11 and 12 digits which is expected accordingly to PPS TBOLT span . I would like to know if I am at the limits of the TBOLT for close in stability measurements and if there is any way to improve that (may be I have missed something). Regards Loïc attachment: tbolt.gif___ 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] 8560E DC Coupling phase noise measurements
Thanks, everything is clear now. I will have a try with a pair of Schottky diodes as 10 db give 3.16 attenuation and so no enough for a +-15V rails , I want to be sure ;=) ) Regards Loïc -Message d'origine- De : time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] De la part de John Miles Envoyé : mardi 25 octobre 2011 22:55 À : 'Discussion of precise time and frequency measurement' Objet : Re: [time-nuts] 8560E DC Coupling phase noise measurements -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Loïc MOREAU Sent: Tuesday, October 25, 2011 1:01 PM To: time-nuts@febo.com Subject: [time-nuts] 8560E DC Coupling phase noise measurements Hi, In the process of measuring phase noise with a 'demphano' gear, I am a bit reluctant to connect my 8560E in DC mode to get 30 Hz low frequency sensitivity: the SA input is very sensitive to DC voltage and may be destroyed by a voltage larger than 200mV. So with a LNA having no blocking DC output I would like to know the best way to protect the SA. I suppose that putting a 100µF capacitor between LNA and SA is not especially a good idea as a charged capacitor to DC rail may have the same effect that no caps at all. I am looking for some advice in that domain to pursue phase noise measurements, for now I connect the SA with a caution after PLL lock and measuring the SA input with a DC voltmeter before switching to DC SA input but this mode of operation is a bit frightening. Any idea ? The 200 mV limit is only with 0 dB of RF attenuation. With a quadrature PLL and LNA, you don't need to use 0 dB. 20 dB is probably OK, and if not, you can make up for it with more gain. A pair of back-to-back Schottky diodes would be another alternative. -- john ___ 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] 8560E DC Coupling phase noise measurements
Hi, In the process of measuring phase noise with a 'demphano' gear, I am a bit reluctant to connect my 8560E in DC mode to get 30 Hz low frequency sensitivity: the SA input is very sensitive to DC voltage and may be destroyed by a voltage larger than 200mV. So with a LNA having no blocking DC output I would like to know the best way to protect the SA. I suppose that putting a 100µF capacitor between LNA and SA is not especially a good idea as a charged capacitor to DC rail may have the same effect that no caps at all. I am looking for some advice in that domain to pursue phase noise measurements, for now I connect the SA with a caution after PLL lock and measuring the SA input with a DC voltmeter before switching to DC SA input but this mode of operation is a bit frightening. Any idea ? Regards Loïc ___ 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] My old new 53132A just arrived
Hi all, My first goal is to verify the frequency of my different RF sources : 4420B, some DDS, a N2PK VNA and ISOTEMP 134-10, the next step with the help of an Excel spread sheet to have some idea about their respective stability. Equipped with option 010, I would like to know how in which direction to go to calibrate my unit. The frequency of the internal time base is supposed to be stable but I have no way to know the exact frequency as the unit is an old one. So I suppose I have to calibrate the gear with an external source, for now I can suppose that my 53132A is accurate to 10-6 or +-1Hz, as it is so easy to turn the front panel adjusting screw, I am not sure about the actual precision. I can take two possible direction to improve my system with an external time base. 1. acquire a rubidium 10Mhz, put in in a box with a 24V power supply Or 2. acquire a 10Mhz GMS time unit or homebrew one with one of the numerous project that we can find. Can somebody give an advice : I have no clue to choose between the solutions, apart the power drain of the first one. Regards Loïc http://www.eai.fr ___ 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] 5350A versus 53131A
In order to compare different frequency sources i am in the process to acquire old Agilent gear, i am looking to different directions 5350A counter or more modern 53131A the prices are nearly equals and I prefer more recent equipment so I somebody can give me an advice to look further on 5350A it will be appreciated. The 225 Mhz frequency limit of the 53131 is not a problem as some equipment are equipped with a 3 Ghz option and it will be possible to construct/buy a prescaler. regards Loïc http://www.eai.fr ___ 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.
