Hi You can do the whole 8 channel distribution amp thing on a pc board for under $10 with logic gates and matching networks. It would cost a bit more if you don’t have the connectors lying around already.
Bob > On Nov 24, 2014, at 12:53 PM, Bill <[email protected]> wrote: > > Hi Luciano, > > Thanks for sharing that data. Do you have a link to the NIST distribution > amplifier? > > When you're ready I hope you'll share more data on your MDT123 design. > > Regards...Bill > > -----Original Message----- > From: time-nuts [mailto:[email protected]] On Behalf Of > [email protected] > Sent: Monday, November 24, 2014 7:14 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps > > > Hi, > > This is a good and reasonable description of what we normally need. I agree. > Some amateur like me want some more than the normal, and If you want, more > than the necessary. This happen only for testing ours ability to improve the > performance of our instruments we use as hobbist. > > For this reason I have developed with the help of three friend a new > solution to distribute or separate a frequency standard. Nothing of > revolutionary or incredible but a mid cost, high performance solution. > I hope the solution will be available mid/end next years in two versions, a > single smd amplifier unboxed to mount it as separator inside an existent > instrument, or a complete single/dual channel (total 12 outputs) with > multiple input possibility in a 1U rack complete of an high performance AC-DC > switchover power supply. > > The file attached is to compare some commercial and NIST solutions with this > amplifier in the single amplifier version. > I will update you using this discussion list. > > Luciano > [email protected] > > > On Mon 24/11/14 1:42 PM , Bob Camp <[email protected]> wrote: > >> Hi >> >> Here’s the problem: >> >> Spectrum analyzers, synthesizers, signal generatros, and the like all >> tend to follow a common design approach. They take the 10 MHz >> reference in and run it through a narrowband PLL. Not every one of them, but >> 99% of them. >> The same is true of microwave multipliers and signal sources. What you >> care very much about is phase noise out to about 100Hz or so. Past >> that, it simply does not matter. >> >> Why? >> >> From the instrument side: >> >> If you are headed to microwaves, the 20 log (N) phase noise formula is >> working against you. 10 MHz multiplied to 100 MHz goes from -170 dbc >> to >> -150 dbc. That’s not what you want to see. They long ago came up with >> the approach of locking up a VHF crystal oscillator to get -170 dbc at 100 >> MHz. >> The technique came out a long time ago (as in before I started doing >> this in the 1970 … or was it the 1790’s …). Cost wise this made sense. >> They bought a cheap(er) OCXO at low frequency if they needed >> stability, and just ran a simple circuit with a crystal in it at VHF. >> >> From the distribution side: >> >> People expected that if they plugged an HPxxxx into a HPyyyy that it >> would meet spec. They even expected it to work if the entire chain was >> not made by HP. Generating -170 level signals is hard enough, >> distributing them across a building, not so much. The designers made a >> simple decision, -145 to -155 dbc/Hz phase noise was “good enough” out >> of a distribution system or out of a master standard. Could they have done >> better? Probably. >> Would it have run up costs in that era? Most certainly. >> >> From a system standpoint: >> >> The people on both ends of the cable made decisions more or less together. >> Who knows who went first or what was tried and failed, that’s buried >> somewhere back in the 1950’s. Did everybody drink the same beverage? >> I’m sure somebody somewhere didn’t. Every piece of HP gear I’ve ever >> seen fits the approach above. Every microwave multiplier I’ve ever >> seen or designed fits it. The Fluke and Comstron gear I’ve worked on >> or actually seen schematics for works this way. Every distribution amp >> or distribution system I’ve seen works this way. I have a nasty habit >> of plugging standard lines into phase noise testers. Each time I do, >> the data I get supports the decision to do things as shown above. >> >> —————— >> >> So what’s this mean? >> >> A simple distribution board made up for less than $10 should do you >> just fine for plugging instruments together. There’s no need to go >> crazy over broadband noise. >> >> Bob >> >>> On Nov 23, 2014, at 10:50 PM, Bill wrote: >>> >>> Hi Bob, >>> >>> Thanks for your comments. >>> >>> The devices in my lab that can benefit from the low phase 10 MHz >>> source >> are 1) the spectrum analyzer(s), 2) a Comstron direct synthesizer, 3) >> the synthesized signal generators and the test source(s) used to drive >> microwave multipliers and signal sources. All these devices will see >> the 10 MHz phase noise (improvements) within the narrowest PLL the devices >> use. >>> >>> After spending "bucks" for a low noise 10 MHz source, I can't afford >>> to >> use one for each instrument. Besides it would hurt to go through the >> trouble of buying a low phase noise 10 MHz reference and lose it in a >> poor distribution amplifier(s). Also, the advantages of running all >> instruments from the same 10 MHz source are well known. >>> >>> So while I was hoping to short circuit some of the >>> design/prototyping >> effort in the hopes someone on this thread had been there, I'll just >> "hit the books" and do some prototyping and noise testing and see what >> I come up with. >>> >>> Regards...Bill >>> >>> -----Original Message----- >>> From: time-nuts [[email protected]] On Behalf Of Bob Camp >>> Sent: Sunday, November 23, 2014 7:08 PM >>> To: Discussion of precise time and frequency measurement >>> Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps >>> >>> Hi >>> >>> While OCXO’s that have -170 dbc/ Hz specs are fairly common, they >> normally go deep inside a box of some sort. It’s a rare off the shelf >> device that takes in the output of a distribution amp *and* requires >> that sort of phase noise. >>> >>> What’s your target device(s)? >>> >>> Why do I ask? Well, a device that has a -170 dbc floor combined with >>> a >> -170 dbc oscillator will give you -167. A device with a -200 dbc floor >> will still “degrade” a -170 dbc oscillator. That’s a fairly big change >> in circuit complexity (and cost) for a 2.9 something db improvement. >> The list of devices that might make it worth spending (say) a few >> hundred dollars a channel versus under a buck a channel is pretty >> short. That may put a bound on this. >>> >>> One example may help: If you are running phase noise testing, forget >> about multi channel distribution amps. They will add a ground loop(s) >> / pickup loop(s) that you will be fighting forever and ever. Do that >> sort of stuff straight off the oscillator. There is no rational amount >> of money (ummm …. errrr … how much do you have?) you can spend to get >> around this. A second (or eighth) oscillator is cheaper than even some >> of the simple approaches that don’t work very well. The type of OCXO >> you are talking about is a < $50 item on eBay. >>> >>> Bob >>> >>> >>>> On Nov 23, 2014, at 9:17 PM, Bill wrote: >>>> >>>> Thanks to all for the response but the distribution amp additive >>>> noise >> can be a real problem since the 10 MHz to be distributed is -170 >> dBC/Hz at >> 10 KHz and needs to be preserved if at all possible. >>>> >>>> BTW, the Ettus Octobox doesn't have a spec for additive phase >>>> noise, so >> that's out. >>>> >>>> Again thanks...Bill >>>> >>>> -----Original Message----- >>>> From: time-nuts [[email protected]] On Behalf Of Bob Camp >>>> Sent: Sunday, November 23, 2014 1:09 PM >>>> To: Discussion of precise time and frequency measurement >>>> Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps >>>> >>>> Hi >>>> >>>> For any “real world” source being distributed, simple high speed >> CMOS buffers will not add enough noise to matter at 10 MHz. That of >> course also assumes that the target gear is the normal bunch of >> instruments that we all play with. >>>> >>>> Bob >>>> >>>>> On Nov 23, 2014, at 11:47 AM, Bill wrote: >>>>> >>>>> What's the latest opinion (data) on available low additive phase >>>>> noise >>>>> 10 MHz amplifiers for 10 MHz distribution? >>>>> >>>>> >>>>> >>>>> Regards and thanks.Bill >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [1] and >>>>> follow the instructions there. >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [2] and >>>> follow the instructions there. >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [3] and >>>> follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [4] >>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [5] >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts [6] and follow >> the instructions there. >> >> >> >> Links: >> ------ >> [1] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-b >> in/ma >> ilman/listinfo/time-nuts[2] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-b >> in/ma >> ilman/listinfo/time-nuts[3] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-b >> in/ma >> ilman/listinfo/time-nuts[4] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-b >> in/ma >> ilman/listinfo/time-nuts[5] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-b >> in/ma >> ilman/listinfo/time-nuts[6] >> http://webmail.timeok.it/parse.php?redirect=https://www.febo.com/cgi-b >> in/ma >> ilman/listinfo/time-nuts >> > Message sent via Atmail Open - http://atmail.org/ > > _______________________________________________ > 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. _______________________________________________ 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.
