Bob, These are good suggestions. I will probably end up doing 1) and 2) you have outlined above.
Thanks! John W. On Thu, Oct 31, 2013 at 7:51 AM, Robert LaJeunesse < [email protected]> wrote: > A couple tricks I've learned along the way: 1) If using a switching supply > is required to get a higher voltage, follow it with a good LDO to reduce > the noise level. I've done this successfully for powering handheld radio > microphones with built-in amplification, video amplifiers, and for > operating a GPS receiver and antenna. 2) If there is a possible ground > current path problem, break the ground path by using a unity gain > "difference" amplifier like the AD8276, or a difference amplifier with gain > like the INA145. The input is differential to the source signal, and the > output has a moderately high impedance reference terminal that can be tied > directly to the load device ground pin. I use this technique all the time > to keep down the noise when driving remote analog loads that have large > ground currents themselves. (Picture a 110W 40MHz transmitter running off > 12V, at the bottom of a stack of other transceivers in the trunk of a > police car - with 40A of > lights flashing, etc.) > > Bob LaJeunesse > > > >________________________________ > > From: "John C. Westmoreland, P.E." <[email protected]> > >To: Discussion of precise time and frequency measurement < > [email protected]> > >Sent: Wednesday, October 30, 2013 10:54 PM > >Subject: Re: [time-nuts] Surface Mount OCXO Questions > > > > > >Graham, > > > >Good points - yes, I have this part currently in the design: TPS75833KTTT > >(LDO from TI) - putting another one down > >(just) for the OCXO isn't a problem. > > > >And a nice 12V rail isn't a problem either since this is for a radio with > a > >nice 12V source. Could I boost the 3.3V rail to > >12V or maybe 5V to 12V - sure - but your point about the switcher is well > >taken and I agree. Having a nice, fat, analog > >ground plane isn't a problem either. > > > >And, this is just a 'dev' board so we can do what we need to make the OCXO > >work as good as possible. > > > >From their spec sheet: '... the supply voltage sensitivity and load > >sensitivity is 5E-11 for a 5 % change in voltage or > >load impedance.' > > > >Thanks, > >John > > > > > > > > > _______________________________________________ > 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.
