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 [mailto:time-nuts-boun...@febo.com] 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 <b...@hsmicrowave.com> 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 [mailto:time-nuts-boun...@febo.com] 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 <b...@hsmicrowave.com> 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 -- 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. _______________________________________________ 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.
