Hi Ok, so what does the math look like with no injection locking:
If you have two equal tones, obviously you have a hard time figuring out which one is the correct 10 MHz. That’s not going to be the situation with a distribution amp. If you have a threat signal that’s 60 db down from the 10 MHz “carrier” that’s a single sideband signal. Run it through a limiter and you get a phase modulated / frequency modulated signal. Frequency modulating your standard line is probably not a good idea. How much FM do you get from a signal X db down? 1) It’s a function of how far off the signal is 2) It’s a function of the level of the signal. 3) It’s a function of the limiter If you have an objective of 1x10^-11 at 1 second, what’s that come out to? Phase sidebands 86 db down at 1 Hz off will put you at 9.6 ppt against your 10 ppt budget. Bob > On Jan 4, 2015, at 11:58 PM, Bill Hawkins <b...@iaxs.net> wrote: > > Thanks, Bruce. That does clear it up, although pulling an oscillator > through a FET gate to a 50 ohm cable seems a stretch. If things are not > that simple, e.g., a wiring harness to a front panel selector switch, > then maybe. I'm assuming the source oscillator is well buffered against > the world outside the oven can. > > I should have said 10base2, not T, meaning coaxial cable with BNC > connectors and T connectors at the receivers, terminated at the far end. > > The allusion to audiophiles had to do with people who pay hundreds of > dollars for a line (mains) cord that has special properties to make the > sound from their amplifier somehow more pleasant. They do this because > marketing told them so, ignoring what goes on in the house wiring to the > wall outlet. > > There are people who need to handle time distribution very carefully > (lest they get FTL neutrinos), but most of the list seems to buy their > equipment from eBay. > > Bill Hawkins > > > -----Original Message----- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce > Griffiths > Sent: Sunday, January 04, 2015 3:39 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Any reason not to use one power amplifierand > splitter for distribution amplifier? > > Almost all frequency counters have an internal source which is a > potential means of injection locking an external reference if the > isolation between the internal source and the external source is > inadequate. High impedance taps on a single terminated line ensure that > the isolation between such internal sources and the shared line is > limited by the isolation afforded by the internal source selection > gating/switching of each device.adding or removing a tap invariably > changes the phase shift between the source and each of the other > receivers.The minimum isolation required can be estimated from the > maximum acceptable frequency shift, the resonator Q and internal reverse > isolation between the source output and the resonator Q. > Frequency distribution systems like the Spectracom 8140 with wide range > ADC tend to degrade the source phase noise significantly with respect to > non agc distribution systems. > > Bruce > > > On Sunday, 4 January 2015 9:41 PM, Bill Hawkins <b...@iaxs.net> > wrote: > > > Friends in Time, > > There's been a large amount of discussion about distribution amps on > this list. > People may be using them just because that's what's done. So I ask you: > > What are we trying to isolate? The destination devices do not generate > an interfering signal, n'est ce pas? > > The receiving devices do not need to have 50 ohms input impedance if the > source cable is properly terminated, no? > > If I use high impedance receivers tapped off a terminated line, how is > this different from 10 base T? > Yes, there will be cable delay between receivers, but how were you going > to avoid that with your distribution amp? > Put another way, why do counters like the Racal 1992 allow you to choose > 50 ohm or high impedance at the input? > > Please, no "take it on faith" audiophile answers. > > HNY. > Bill Hawkins > > > _______________________________________________ > 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.