hp_cisco...@yahoo.com said: > One thing I am wondering about is disciplining - how much of this is HW and > how much is SW?
> How are non-Trimble oscillators disciplined? It it common practice to > provide a GPS antenna input? I think you are missing the big picture. There are two different types of boxes. There are oscillators. They come in all types of quality. Many of the good ones include an oven to keep the crystal at a constant temperature. OCXO is a common term: Oven Controlled Crystal Oscillator. There are GPSDOs: GPS Disciplined Oscillators, for example the Trimble Thunderbolt. They generally start with a good crystal, then add a GPS unit, some hardware to compare the crystal output with the GPS output, and a microprocessor and software to control everything. Crystals can be tuned slightly by changing the capacitance in parallel with the crystal. You can do that by using a diode for the capacitor and changing the back-bias across the diode. Usually, that voltage comes from a DAC. "Discipline" just means making it do what you want. Usually, that's put out the right time and/or frequency. GPS is a handy way to get both time and frequency. GPS and a good crystal are a good fit. GPS has lots of short term noise but very very good long term accuracy. Crystals have good short term stability but lots of long term drift. > How are non-Trimble oscillators disciplined? Any way you want. Whatever fits your application. One approach is to adjust something with a screwdriver. You have to do that frequently enough so that it meets your needs. Usually, crystals come with specs, things like max drift over a month or year. So you can figure out if you need to calibrate it monthly or annually. It's easier to get better accuracy with GPS. You might have fun browsing data sheets. Feed OCXO to google and see what you get. There is lots of info available on the HP Z3801A. http://www.realhamradio.com/GPS_Frequency_Standard.htm (Time sink warning.) -- These are my opinions. I hate spam. _______________________________________________ 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.