Re: [time-nuts] On choosing reasonable synthesizer PN requirements
Hi Assuming you know the power level you will be delivering to the sat and the noise figure of the receiver on the sat, the calculation is just as presented earlier. If the antenna on the sat has gain, that also gets into this and that. Using some made up numbers, since I do not have the real ones for this exact system: You start out with +50 dbm ERP from your antenna. You have a link loss of 190 db. The sat antenna has 1 db of gain. You are delivering 50 - 190 + 1 = -139 dbm to the sat. If the noise figure of the sat reciever is 3 db, then it’s noise floor is -174 + 3 = -171 dbm That puts a limit on the uplink signal at 171 - 139 = -32 dbc. If the noise on your transmitted signal is 32 db down, you will degrade the SNR at the sat by 3 db. ( = they add as power not voltage). You will need to do some research with Mr Google to come up with the real numbers to plug into the calculations. They are different for each system design ( your antenna, your erp ….). Bob > On Apr 24, 2020, at 9:37 AM, Karen Tadevosyan via time-nuts > wrote: > > Hello Bill, > > > > Thank you for the clarification. It is especially pleasant that our opinions > are 100% the same. > > However, I would like to find some tool for calculating the balance of the > radio link in order to understand exactly the reasonable requirements for > synthesizer's PN. > > The issue of stability is now gone - I use a good OCXO with the well-known > Allan deviation values > (http://www.ra3apw.ru/wp-content/uploads/2020/04/OCXO_Allan_dev_photo-768x48 > 3.jpg & > http://www.ra3apw.ru/wp-content/uploads/2019/10/OCXO_AllanDeviation_1-768x37 > 4.jpg ) and sufficient stability is confirmed by the successful work in FT8 > mode via QO-100. > > > > Regards, > Karen ra3apw > > > >> Hello Karen, > >> As a general rule of thumb, if uplink LO phase noise power ends up being > >> at least 15-20dB below the expected kTB noise received at the satellite > >> transponder, its contribution is not really significant. With -98dBc-Hz, > >> on Tx, you should be in good shape because, to simplify things a bit, > >> Tx SNR at the transmitter far exceeds the SNR at the QO-100 receive > >> antenna. Thermal noise from the antenna and receiver LNA will dominate > >> the received signal noise at the satellite. It's more important to keep > >> your Tx frequency stable. A GPSDO or Rb reference will be useful here. > >> It's also important to keep the DL 10.45GHz receive on frequency as well > >> (even more important, given the freq. multiplication up to 10GHz). > >> > >> On the DL side, antenna temperature and LNA noise should be the dominant > >> signal degradation factors, so good antenna/LNA G/T is all-important. > >> > >> Cheers, > >> Bill > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
Hi again Karen, Have you seen this app designed specifically for the Es'hail QO-100? https://play.google.com/store/apps/details?id=com.antmodstudios.eshail2linkbudget=nl Any extra margin on C/N0 can be used to estimate permissible LO phase noise. Otherwise, you can put together a link budget in Excel or Libreoffice to add whatever parameters you want. Cheers, Bill On 24.04.20 15:37, Karen Tadevosyan via time-nuts wrote: Hello Bill, Thank you for the clarification. It is especially pleasant that our opinions are 100% the same. However, I would like to find some tool for calculating the balance of the radio link in order to understand exactly the reasonable requirements for synthesizer's PN. The issue of stability is now gone - I use a good OCXO with the well-known Allan deviation values (http://www.ra3apw.ru/wp-content/uploads/2020/04/OCXO_Allan_dev_photo-768x48 3.jpg & http://www.ra3apw.ru/wp-content/uploads/2019/10/OCXO_AllanDeviation_1-768x37 4.jpg ) and sufficient stability is confirmed by the successful work in FT8 mode via QO-100. Regards, Karen ra3apw Hello Karen, As a general rule of thumb, if uplink LO phase noise power ends up being at least 15-20dB below the expected kTB noise received at the satellite transponder, its contribution is not really significant. With -98dBc-Hz, on Tx, you should be in good shape because, to simplify things a bit, Tx SNR at the transmitter far exceeds the SNR at the QO-100 receive antenna. Thermal noise from the antenna and receiver LNA will dominate the received signal noise at the satellite. It's more important to keep your Tx frequency stable. A GPSDO or Rb reference will be useful here. It's also important to keep the DL 10.45GHz receive on frequency as well (even more important, given the freq. multiplication up to 10GHz). On the DL side, antenna temperature and LNA noise should be the dominant signal degradation factors, so good antenna/LNA G/T is all-important. Cheers, Bill ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
On Fri, Apr 24, 2020 at 8:08 AM jimlux wrote: > On 4/24/20 5:52 AM, David J Taylor via time-nuts wrote: > > Hi > > > > The “wiggles” he is chasing are about 2-3 Hz (by eyeball on his charts). > > At 2.4 GHz, > > that is a fairly convenient ~1 ppb. The Z-3801 (if it was in good > > health) should be easily > > able to hold that level of performance. It’s not clear which MD-011 he > > is using, but it is > > a pretty good bet it will also hold that level as well. The usual > > disclaimers about good > > satellite view for the GPSDO’s would of course apply. > > > > Substituting a typical telecom Rb for either device would likely also > > allow the wiggles > > to be observed (or not). That would take out the whole dependence on GPS. > > > > (Yes I realize those comments are probably better directed to those > > involved ….). > > > > Bob > > > It's a fascinating writeup - the author does time-nut like stuff at > work, so he looked at the possibilities - is the GPSDO at Bochum > screwing up (can't actually get in because of COVID-19) - so he compares > with a locally generated uplink. > He also compares with the signal from an uplink from Mauritius, so the > Doppler is slightly different. > > I'm going to guess just what he said at the end - some sort of thermal > thing on the spacecraft. > And I would guess the battery charging system. I would love to see the bus voltage plot superimposed on the The "wiggles". (Is the housekeeping telemetry decodable?) Notice that the frequency "pop" in the beacon coincides with the end of the "wiggles". I haven't looked but does the bird have a planar PV array? If so, I am guessing that this is when the charging system shuts down as the PV array stops producing output and then shortly thereafter something else turns off or turns on, the two events creating the leading and trailing edges of the "pop". If it has a max PPT charging system (of course it does) I can imagine, as the output of the array falls off, the MPPT algorithm "hunting" to find an optimum operating point and causing bus voltage to vary. Of course, it could always be the Radar Men from the Moon. -- Brian Lloyd 706 Flightline Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
On 4/24/20 5:52 AM, David J Taylor via time-nuts wrote: Hi The “wiggles” he is chasing are about 2-3 Hz (by eyeball on his charts). At 2.4 GHz, that is a fairly convenient ~1 ppb. The Z-3801 (if it was in good health) should be easily able to hold that level of performance. It’s not clear which MD-011 he is using, but it is a pretty good bet it will also hold that level as well. The usual disclaimers about good satellite view for the GPSDO’s would of course apply. Substituting a typical telecom Rb for either device would likely also allow the wiggles to be observed (or not). That would take out the whole dependence on GPS. (Yes I realize those comments are probably better directed to those involved ….). Bob It's a fascinating writeup - the author does time-nut like stuff at work, so he looked at the possibilities - is the GPSDO at Bochum screwing up (can't actually get in because of COVID-19) - so he compares with a locally generated uplink. He also compares with the signal from an uplink from Mauritius, so the Doppler is slightly different. I'm going to guess just what he said at the end - some sort of thermal thing on the spacecraft. If you follow his Twitter feed: https://twitter.com/ea4gpz I think it's all but certain that it's the local oscillator in the satellite-borne transponder is the cause of the problem. He's looked at an engineering beacon on the satellite too. The orbital calculations involved need to be quite accurate. I thought it might interest those chasing the ultimate precision! Probably ought to change the title of this topic, but I'm unsure of the protocol here about so doing. Cheers, David ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
Hi The “wiggles” he is chasing are about 2-3 Hz (by eyeball on his charts). At 2.4 GHz, that is a fairly convenient ~1 ppb. The Z-3801 (if it was in good health) should be easily able to hold that level of performance. It’s not clear which MD-011 he is using, but it is a pretty good bet it will also hold that level as well. The usual disclaimers about good satellite view for the GPSDO’s would of course apply. Substituting a typical telecom Rb for either device would likely also allow the wiggles to be observed (or not). That would take out the whole dependence on GPS. (Yes I realize those comments are probably better directed to those involved ….). Bob If you follow his Twitter feed: https://twitter.com/ea4gpz I think it's all but certain that it's the local oscillator in the satellite-borne transponder is the cause of the problem. He's looked at an engineering beacon on the satellite too. The orbital calculations involved need to be quite accurate. I thought it might interest those chasing the ultimate precision! Probably ought to change the title of this topic, but I'm unsure of the protocol here about so doing. Cheers, David -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
Hi The “wiggles” he is chasing are about 2-3 Hz (by eyeball on his charts). At 2.4 GHz, that is a fairly convenient ~1 ppb. The Z-3801 (if it was in good health) should be easily able to hold that level of performance. It’s not clear which MD-011 he is using, but it is a pretty good bet it will also hold that level as well. The usual disclaimers about good satellite view for the GPSDO’s would of course apply. Substituting a typical telecom Rb for either device would likely also allow the wiggles to be observed (or not). That would take out the whole dependence on GPS. (Yes I realize those comments are probably better directed to those involved ….). Bob > On Apr 24, 2020, at 6:52 AM, David J Taylor via time-nuts > wrote: > > From: Karen Tadevosyan via time-nuts > > Hi, > > one of the interesting HAM radio topic in Europe now is the use of the new > geostationary satellite Phase-4A (QO-100) for analog and digital modes via a > 2.4/10 GHz transponder. > [] > === > > ... and Time-Nuts may be interested in some oscillator measurements made by > Daniel Estévez showing some unexpected steps. His blog is here: > > https://destevez.net/2020/04/wiggles-in-the-qo-100-local-oscillator/ > > It's a fascinating story, and may not yet be complete. > > Daniel is a GNSS Engineer by occupation. > > Cheers, > David GM8ARV > -- > SatSignal Software - Quality software for you > Web: http://www.satsignal.eu > Email: david-tay...@blueyonder.co.uk > Twitter: @gm8arv > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
Hello Karen, As a general rule of thumb, if uplink LO phase noise power ends up being at least 15-20dB below the expected kTB noise received at the satellite transponder, its contribution is not really significant. With -98dBc-Hz, on Tx, you should be in good shape because, to simplify things a bit, Tx SNR at the transmitter far exceeds the SNR at the QO-100 receive antenna. Thermal noise from the antenna and receiver LNA will dominate the received signal noise at the satellite. It's more important to keep your Tx frequency stable. A GPSDO or Rb reference will be useful here. It's also important to keep the DL 10.45GHz receive on frequency as well (even more important, given the freq. multiplication up to 10GHz). On the DL side, antenna temperature and LNA noise should be the dominant signal degradation factors, so good antenna/LNA G/T is all-important. Cheers, Bill On 24.04.20 08:04, Karen Tadevosyan via time-nuts wrote: Hi, one of the interesting HAM radio topic in Europe now is the use of the new geostationary satellite Phase-4A (QO-100) for analog and digital modes via a 2.4/10 GHz transponder. For my transverter (input from a UHF transceiver) in TX mode I use a 1968 MHz LO with a phase noise level -98 dBc/Hz @ 10 kHz. It is possible to do LO with the best parameters but every next 10 dB increases the cost and complicates the decision. My question is: How to calculate/evaluate the reasonable phase noise requirements of a transverter's LO which would not lead to degradation of the performance of 2400 MHz radio uplink and 10 GHz downlink on the Earth - Analog Satellite Transponder - Earth path? Thanks. Karen, ra3apw ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] On choosing reasonable synthesizer PN requirements
From: Karen Tadevosyan via time-nuts Hi, one of the interesting HAM radio topic in Europe now is the use of the new geostationary satellite Phase-4A (QO-100) for analog and digital modes via a 2.4/10 GHz transponder. [] === ... and Time-Nuts may be interested in some oscillator measurements made by Daniel Estévez showing some unexpected steps. His blog is here: https://destevez.net/2020/04/wiggles-in-the-qo-100-local-oscillator/ It's a fascinating story, and may not yet be complete. Daniel is a GNSS Engineer by occupation. Cheers, David GM8ARV -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
