A stand alone ocxo, like the ones frequently used as time base in good quality electronic counters, are very good, but you have to wait a couple of months of continuous operation before they slowly end to drift. So you can calibrate them with a good reference after this long period of start-up and go ahead for many months or years with very good accuracy. But never switch the ocxo off! :-). Have fun. Luca iw2lje
Il giorno sab 26 gen 2019 17:01 DM <[email protected]> ha scritto: > Bob, > Please advise the make & model of your counter, and if possible, the make > & model of the OCXO it contains, or if you have the manual, the aging spec > on the time base. It's entirely possible (probable) that the OCXO is > already several orders of magnitude better than any HF WWV broadcast. BTW, > higher frequency broadcasts are much more susceptible to atmospheric shifts > than lower frequencies. That's why WWVB at 60KHz was used for many years as > a traceable standard. > How long has it been since its last real calibration (not beating against > WWV, but properly calibrated)? > I agree with the others who have advised in favor of a GPSDO. A second > approach would be a Rubidium standard. Much more stable than a stand-alone > OCXO, and they don't need an antenna. But, you would need to be assured > that it's properly calibrated when you buy it. Ebay seller rdr-electronics > sells Rb oscillators, and I'm pretty sure those they sell are properly > calibrated before they ship them out. Good folks. > Since you live in the LA area, surely there are other hams in the area who > have the ability to properly adjust the time base in your counter. Get on > the air and ask around. Might be someone just a couple of blocks away who > has all you need. > > > Cheers, > Dave M > > ----- Original Message ----- > > From: "Bob Albert via time-nuts" <[email protected]> > To: "Discussion of precise time and frequency measurement" < > [email protected]> > Cc: "Bob Albert" <[email protected]> > Sent: Saturday, January 26, 2019 12:06:43 AM > Subject: Re: [time-nuts] Frequency standard > > Paul, thanks for your reply. > You ask what I want to accomplish. Basically I just want to be able to > calibrate the OCXO in my counter. I don't get a good enough signal from WWV > and don't really have a proper method for adjustment. > I listen to the highest froquency WWV I can hear, and these days it's > probably only 10 MHz. I listen on a communications receiver to my counter > and to WWV beating. As I watch the S meter, the pulsing gets slower and > slower as I zero in, and at some point the pulsing is lost because the > atmospheric fading masks it. That's usually around one fade every couple of > seconds, for an accuracy of only about 1 part in 20 million. I want it > somewhat better, but no way do I need it 100 times better. If I could set > it within 0.1 Hz that would be fine - it would enable frequency measurement > at 100 MHz with pretty good confidence, less so at 500 MHz. I used to be > able to hear 20 and 25 MHz from WWV but those days are gone. Even then, the > confidence level is a bit poorer than I'd like. > So maybe a GPSDO would help but it seems the cost is out of proportion to > my needs. > Bob > On Friday, January 25, 2019, 9:01:59 PM PST, paul swed < > [email protected]> wrote: > > Bob > The gpsdos will be far superior to the method you are currently using. I > will guess 100-1000 times better and higher. I took a quick look at EBAY > boy there are lot of them these days. We all have our favorites. Trimbles, > HPs... But what would help is understanding your need. What do you want to > accomplish. > Regards > Paul > WB8TSL > > On Fri, Jan 25, 2019 at 9:05 PM Bob Albert via time-nuts < > [email protected]> wrote: > > > Please excuse my ignorance but I have been trying to improve on my > > frequency calibration. > > I have always used WWV but when I try to get really close in frequency, > > the beat and the fading are difficult to separate. > > Someone suggested I get a GPSDO to refine my 10 MHz. I looked around and > > have seen a few, mostly in the $100 range, but before I shell out fot > > something I know little about I wonder if someone can give me a short > > tutorial or at least some advice on what I need to do. > > I live in Los Angeles so I imagine signals would be reasonably strong. > > But what hardware and software do I need? I want 10 MHz to put into my > > counter or, at least, to calibrate the time base in the counter. I > prefer > > the latter, since that means I won't have to receive GPS signals in > order > > to measure frequency. Most of the time I don't need really accurate > > results. > > I could run an outdoor antenna if needed. What receiver ought I look > > into, how much budget do I need, and all the other questions relating to > > this subject. > > And finally, how much frequency error can I expect? > > Bob > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
