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.