On Tue, 17 Jan 2006 17:42:51 -0800, "Tom Van Baak" <[EMAIL PROTECTED]> wrote:
>Nice set of questions. > >You can find more info if you hunt around my website: > > http://www.LeapSecond.com > >My very rough guess is that used Rb are available >for $100 to $500 and used Cs are available for $500 >to $2500. > >Most Rb last longer than a timekeeping hobby lasts. >Rb tend to be much smaller, require less power, are >available in much larger quantities (the used market >is flooded with them; they show up on eBay every day). >Rb have pretty good short-term stability, although a >really good quartz will blow them away. It all depends >on your needs. Hi Tom and list, I thought this would be a good time to de-lurk, introduce myself and ask some questions. First off, Tom, I'm blown away with your shop and accomplishments. I thought I had a nice instrumentation shop.... Several questions. I have a box full of Trimble ACE III OEM GPS receivers and active antennae. I have one set up more or less permanently on my bench as the source of a 1 pps signal. Here's what the manual says about the 1 PPS signal: The timing accuracy is ± 100 nanosecond (1 sigma) and is available only when valid position fixes are being reported. Repeatability checks of 10 sets of 100 one second samples taken over a period of 20 minutes showed an average variation of approximately 100 nanoseconds (not allowing for SA)." The max rise time of the 1pps signal is less than 20ns. Elsewhere in the manual it says that the 12.504 mhz crystal oscillator is spec'ed as follows: "Tolerance - +-1ppm at 20deg C. Temperature stability - 2.5ppm/deg C." I'm trying to determine what to make of these specs in terms of the accuracy of the 1PPS signal as a timing signal. Not necessarily accuracy as relates to GMT but to the actual 1.000xxx pps signal. 1E-7 doesn't seem all that good for GPS. Can I assume that the actual timing accuracy is better? Jitter? I'd like to use this signal as a gating signal for one of my frequency counters. Would this be better or worse than the un-ovenized TCXO? This is an 80s vintage HP counter, sorry I don't have the model handy. I should be able to improve the receiver performance some by ovenizing it. I wonder if it would be worth the effort? Next question. I have a 70s vintage HP ovenized 10 mhz frequency standard like the one that they sold as an OEM item and as used in some counters. It's in the oversized metal relay can. I'd have to open the case to get the model number but I do recall the -01 option, high stability. I have this unit mounted in a case along with a power supply and have used it for 20+ years as my frequency standard. It's been powered more or less all that time and as determined by beating it against the 10 mhz WWV signal, has settled down and is more stable I have the patience to watch the scope. If I divided this down to 1 PPS, would it be a better timing reference than the GPS receiver? Is there a better method of calibrating this oscillator than beating it against WWV, assuming the usual compliment of electronic lab equipment but no special timekeeping instruments? Next, I really want one of David Forbes' CRT clocks! I sent Dave an email asking if he's planning on making any more but I haven't heard back. (you lurking here, Dave?) Anyone have one in good condition he'd like to part with? Prefer the clear case. Guess that's enough for now. Thanks, John --- John De Armond See my website for my current email address http://www.johngsbbq.com Cleveland, Occupied TN A foolish consistency is the hobgoblin of little minds.-Ralph Waldo Emerson _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
