Hi Everyone, I'm newer to this forum but I really enjoy reading the discussions. I have a pretty basic question. I'm wondering why one would chose an Rb Oscillator over a traditional OCXO? It does not immediately appear there is a phase noise advantage in the Rb.. Thanks, ~Shane
On Fri, Apr 25, 2014 at 10:00 AM, <[email protected]> wrote: > Send time-nuts mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of time-nuts digest..." > > > Today's Topics: > > 1. Low SNR GPS reception and cheap LNAs (Attila Kinali) > 2. Re: Symmetricom chip scale atomic clock (Tom Knox) > 3. Re: How to accurately measure an oscillator's temperature. > (Didier Juges) > 4. Re: Low SNR GPS reception and cheap LNAs (Chris Albertson) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 25 Apr 2014 15:28:22 +0200 > From: Attila Kinali <[email protected]> > To: [email protected] > Subject: [time-nuts] Low SNR GPS reception and cheap LNAs > Message-ID: <[email protected]> > Content-Type: text/plain; charset=US-ASCII > > Hi, > > I recently bought a bladeRF[1] to experiment a bit with GPS decoding. > > I tried to get GNSS-SDR[2] which seems quite good, but has its flaws. > One of the things was that i cannot seem to get a fix in my environment. > One of the problems seems that my antenna position is far from optimal. > Aparently, GNSS-SDR uses only a very rudimentary acquisition technique > (at least so i have been told). Now i wonder what techniques for low SNR > acquisition are around. Would someone be so kind and give me some key > words to google for? > > I also am looking to add an LNA to my reception chain, which is a > mix of a 50R antenna with 75R Coaxcable (sat coax stuff is just a lot > cheaper :-). Has anyone a recomendation for a good LNA that can be used > in a flying construction (soldering onto two back-to-back glued > connectors)? > Ie it shouldnt be a QFN or BGA. DFN works but i'd rather have something > with pins, like SC-70/SOT-323 or similar/larger. > > > Attila Kinali > > > [1] www.nuand.com/bladeRF > [2] www.gnss-sdr.org > > -- > The trouble with you, Shev, is you don't say anything until you've saved > up a whole truckload of damned heavy brick arguments and then you dump > them all out and never look at the bleeding body mangled beneath the heap > -- Tirin, The Dispossessed, U. Le Guin > > > ------------------------------ > > Message: 2 > Date: Fri, 25 Apr 2014 08:53:25 -0600 > From: Tom Knox <[email protected]> > To: Time-Nuts <[email protected]> > Subject: Re: [time-nuts] Symmetricom chip scale atomic clock > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > For the sake of discussion let me just add that even if medesigns comments > were true of Microsemi, the Microsemi responses on this form have been from > long time Time-Nuts who have for years contributed their knowledge to the > betterment of the community in the proudest traditions of acadimia. Never > have I seen them use the form for financial gain. Sure corporate greed is a > problem in todays society but knowing some of the individuals at Microsemi > it is clearly not a black and white issue. Further where it may be > acceptable in some cases to release a product early and perform some of the > final development on the backs of the customers to better serve their needs > such as in the case of the fantastic "TimeLab". In a mission critical > product like the CSAC a problem like this will cost Microsemi far more then > they would profit from a premature release. These manufacturing defects > were clearly something they could not anticipate. I for one will be > purchasing many more Microsemi products > in the future and viewing their performance on TimeLab with full > confidence. Please keep the group update on your progress resolving this > issue. It will be interesting to see if a single point of failure is found, > a smoking gun so to speak; or whether it will be resolved with a number of > minor changes during product evolution. In any case I hope the problem is > resolved quickly. > > Thomas Knox > > > > > Date: Fri, 25 Apr 2014 08:14:06 +0200 > > From: [email protected] > > To: [email protected] > > Subject: Re: [time-nuts] Symmetricom chip scale atomic clock > > > > On Fri, 25 Apr 2014 08:33:06 +0300 > > MailLists <[email protected]> wrote: > > > > > The recently acquired cash cow isn't working exactly as > > > expected/advertised. We still don't have a clue when/if the fundamental > > > (as in physics laws) design (we can't officially blame the cheap > Chinese > > > manufacturer) flaw will be fixed (manufacturer replaced), but as our > > > main customer, which is used to (literally) blow up tons of (others') > > > money, isn't very concerned (for now), and the profit margin is (still) > > > high enough to replace (no questions asked, for the time being) the > > > failed units of the other (civilian/commercial) customer(s). > > > > Sorry, but this is was not necessary. > > Not every company is evil and not every company just works for the > > short term bottom line. > > > > It is very normal that problems show up in series production which > > were not visible before in the prototypes or pre-series production. > > It's part of the very nature how volume production work. And no, > > you cannot always attriubute it to less care taken in the volume > > production than in the pre-series. Some flaws are only visible if > > you get enough produced and then it's still one in a couple hundred > > if not a one in a couple hundred thousand. > > > > Every product i was ever involved with had some flaws uncovered during > > series production. Even if the gratest care was taken. IMHO it does not > > matter whether the product has a shows suddenly a flaw or not, but how > > the manufacturer reacts to it. And as it seems Microsemi is replacing > > the failing units without causing trouble. > > > > Also, please be aware that fixing a flaw that only very few units show > > is not an easy thing. You cannot just build a prototype and be sure > > that the bug is gone. You have to first produce enough to have a > statistical > > significant sample size. This all takes time, weeks, months, or even > years. > > > > > > So, please refrain from spreading false rumors that anyone is ignoring > the > > issue when aparently the contrary is the case. > > > > > > Attila Kinali > > > > PS: Disclaimer: i neither work for or have any ties with Microsemi or > > Jacksonlabs. > > > > -- > > I pity people who can't find laughter or at least some bit of amusement > in > > the little doings of the day. I believe I could find something ridiculous > > even in the saddest moment, if necessary. It has nothing to do with being > > superficial. It's a matter of joy in life. > > -- Sophie Scholl > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > ------------------------------ > > Message: 3 > Date: Fri, 25 Apr 2014 10:14:03 -0500 > From: Didier Juges <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] How to accurately measure an oscillator's > temperature. > Message-ID: <[email protected]> > Content-Type: text/plain; charset=UTF-8 > > The best way is to place the temperature sensor near the part or parts > that are the most temperature sensitive. When dealing with something that > is already in an oven, that may not be so easy. > > Didier KO4BB > > On April 23, 2014 9:37:29 PM CDT, Chris Albertson < > [email protected]> wrote: > >I have both an OCXO and an FE-5680 Rb oscillator and I'd like to track > >their temperatures. > > > >What is the best why to measure? Maybe each has a different best > >method > > > >The OCXO is just a small steel can. Is measuring the steel can > >temperature > >the best why to go. Epoxy some kind of sensor to it? > > > >The Rb is mounded to a large heat sink and there is a fan. I want to > >control the fan so as to keep the Rb temperature constant. > > > >In both cases I tried using TMP36 three terminal sensors and just got > >noise. The reported temperature was up and down more than 2C. The > >fan > >controller just chases noise. > > > >BTW the fan based temperature control is effective. The FE5680 gets > >very > >warm in it's box but if I give the 12V fan even 8 volts the heat sink > >quickly cools. I want to throttle the fan to keep the Rb at constant > >temperature but the temperature data I'm getting is not very good. > > > >The problem I think is that any sensor I have is on the outside of the > >oscillator and is effected by cooling air What are others doing? > >What's > >the best kind of sensor. > > > >-- > > > >Chris Albertson > >Redondo Beach, California > >_______________________________________________ > >time-nuts mailing list -- [email protected] > >To unsubscribe, go to > >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >and follow the instructions there. > > -- > Sent from my Motorola Droid Razr 4G LTE wireless tracker while I do other > things. > > ------------------------------ > > Message: 4 > Date: Fri, 25 Apr 2014 08:42:16 -0700 > From: Chris Albertson <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] Low SNR GPS reception and cheap LNAs > Message-ID: > <CABbxVHsgpzoeptP-GaY2sBuQ67k4WJF-B534XBAXbxA= > [email protected]> > Content-Type: text/plain; charset=UTF-8 > > On Fri, Apr 25, 2014 at 6:28 AM, Attila Kinali <[email protected]> wrote: > > > Hi, > > > > I recently bought a bladeRF[1] to experiment a bit with GPS decoding. > > > > I tried to get GNSS-SDR[2] which seems quite good, but has its flaws. > > One of the things was that i cannot seem to get a fix in my environment. > > One of the problems seems that my antenna position is far from optimal. > > Aparently, GNSS-SDR uses only a very rudimentary acquisition technique > > (at least so i have been told). Now i wonder what techniques for low SNR > > acquisition are around. Would someone be so kind and give me some key > > words to google for? > > > > I also am looking to add an LNA to my reception chain, which is a > > mix of a 50R antenna with 75R Coaxcable (sat coax stuff is just a lot > > cheaper :-). Has anyone a recomendation for a good LNA that can be used > > in a flying construction (soldering onto two back-to-back glued > > connectors)? > > Ie it shouldnt be a QFN or BGA. DFN works but i'd rather have something > > with pins, like SC-70/SOT-323 or similar/larger. > > > > You best bet is to change out the antenna. You can buy them with a higher > built-in gain up to about 40dB. My understanding is that designing a GOOD > LNA is not so easy as little things like the exact layout of the PCB and > how the PCB transitions to connectors matters a lot. But you can buy these > ready made for cheap. I've seen complete LNAs in an enclosure with > connectors at good prices on eBay. The user manuals I have say using 75R > cables with compression type F connects is OK. I doubt the cheaper type > f-connectors would work well. > > I have a good high quality Tremble in-line amplifier with N-connector and > the ability to pass DC. In my experiment I place the antenna indoor and > use amplifier and then outdoors with no amplifier. I get MUCH better > results with my 26dB gain antenna on the roof and 25 feet of cable than > with indoor amplified antenna with short cable. My un-scientific > conclusion was that amplified noise is still noise. > > > > > > > Attila Kinali > > > > > > [1] www.nuand.com/bladeRF > > [2] www.gnss-sdr.org > > > > -- > > The trouble with you, Shev, is you don't say anything until you've saved > > up a whole truckload of damned heavy brick arguments and then you dump > > them all out and never look at the bleeding body mangled beneath the heap > > -- Tirin, The Dispossessed, U. Le Guin > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > > -- > > Chris Albertson > Redondo Beach, California > > > ------------------------------ > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > End of time-nuts Digest, Vol 117, Issue 94 > ****************************************** > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
