Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion)
My perpetually drifting 10811 pretty quickly made it to the negative voltage rail on the control voltage. I was looking at the oscillator output with an O-scope and it looked pretty nasty. My equipment is not so hot, so I first chalked that up to bad probes. But I did some google work on that and found an old time-nuts message thread about the 10811 looking bad if the output impedance is bad. The VE2ZAZ board has provision for a 50 ohm resistor on the oscillator output. I have one on the board but it is a little-bitty thing, maybe 1/8th of a watt? Something I probably got from the guts of a VCR or whatnot. Hmm. So I put in a 1/4 watt 50 ohm resistor (like the parts list called for). My working hypothesis is that the small resistor was changing impedance due to heat. I have reset the control voltage to center value and got the coarse trimmer all beautifully centered. It's been running for about a day and I am hopeful that I've made a difference. So far so good. While I was interrupting the flow of 10 Mhz, I also mapped out the control voltage and corresponding digital control value and an approximate frequency. You EE guys are probably snickering and will want to tear the epaulettes off my time-nuts coat and break my sword. What can I say. ___ 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.
Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion)
Unfortunately, experience is a lantern lighting the way already done... and it takes months to forge a good sword: no one should break any sword. On Fri, Nov 9, 2012 at 10:53 PM, Chris Howard ch...@elfpen.com wrote: My perpetually drifting 10811 pretty quickly made it to the negative voltage rail on the control voltage. I was looking at the oscillator output with an O-scope and it looked pretty nasty. My equipment is not so hot, so I first chalked that up to bad probes. But I did some google work on that and found an old time-nuts message thread about the 10811 looking bad if the output impedance is bad. The VE2ZAZ board has provision for a 50 ohm resistor on the oscillator output. I have one on the board but it is a little-bitty thing, maybe 1/8th of a watt? Something I probably got from the guts of a VCR or whatnot. Hmm. So I put in a 1/4 watt 50 ohm resistor (like the parts list called for). My working hypothesis is that the small resistor was changing impedance due to heat. I have reset the control voltage to center value and got the coarse trimmer all beautifully centered. It's been running for about a day and I am hopeful that I've made a difference. So far so good. While I was interrupting the flow of 10 Mhz, I also mapped out the control voltage and corresponding digital control value and an approximate frequency. You EE guys are probably snickering and will want to tear the epaulettes off my time-nuts coat and break my sword. What can I say. ___ 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. ___ 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.
Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion)
Chris HP 10811 can't drift that much that fast unless something is near broken, or being connected wrong like gnds or PS voltage. Check the operation of the oven. It must be close and sort of working otherwise it would not be on freq as close as it is, but maybe it is drifting. The other thing to check is what it is being compared to. Are you sure it is the 10811 drifting and not your comparison reference? Also Triple check to make sure the input to the EFC is not causing a problem the way you are using it by grounding the EFC and count the cycle time for a beat freq. If the freq is close to your reference, Adjust the 10811 to get a beat freq between the two 10 MHz signals or use a scope and Sync on the reference osc and time the drift rate of the 10811 osc a few times a day to see if the drift rate is changing. A position change on the scope of 1ns /sec = 1e-9 freq offset, 1ns /10 sec is 1e-10, etc. If all you have for comparison is a 1 pps from an unknown if working GPS's 1pps, then sounds like it is time to get something else to break the tie to see which is really broken. With the high freq drift rate of 1Hz that you are seeing, you could use a wwv receiver. ws * [time-nuts] getting a grip on 10811 drift (beginner-ishquestion) Chris Howard Fri Nov 9 21:53:39 UTC 2012 My perpetually drifting 10811 pretty quickly made it to the negative voltage rail on the control voltage. I was looking at the oscillator output with an O-scope and it looked pretty nasty. My equipment is not so hot, so I first chalked that up to bad probes. But I did some google work on that and found an old time-nuts message thread about the 10811 looking bad if the output impedance is bad. The VE2ZAZ board has provision for a 50 ohm resistor on the oscillator output. I have one on the board but it is a little-bitty thing, maybe 1/8th of a watt? Something I probably got from the guts of a VCR or whatnot. Hmm. So I put in a 1/4 watt 50 ohm resistor (like the parts list called for). My working hypothesis is that the small resistor was changing impedance due to heat. I have reset the control voltage to center value and got the coarse trimmer all beautifully centered. It's been running for about a day and I am hopeful that I've made a difference. So far so good. While I was interrupting the flow of 10 Mhz, I also mapped out the control voltage and corresponding digital control value and an approximate frequency. You EE guys are probably snickering and will want to tear the epaulettes off my time-nuts coat and break my sword. What can I say. ___ 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.
Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion)
Hi If you have one of the 10811's out of a Z3801, then it's EFC range is ~ 10X a normal part. There apparently are other odd EFC ranges out there. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Howard Sent: Monday, November 05, 2012 4:53 PM To: time-nuts@febo.com Subject: Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion) On 11/5/2012 3:16 PM, Richard H McCorkle wrote: The EFC specs on a 10811 are a frequency change of 1 Hz over a -5v to +5v EFC span or a sensitivity of roughly 1e-8 per volt (varies widely up to about 3e-8 / volt on some units) so you can get a ballpark idea of the age rate by looking at the EFC voltage change over 24-hour periods. I have been running it continuously for quite a while. I fired it up from cold start early this year and have had it running almost continuously, just a few power cycles in that time. Over the period of three weeks ending today the control voltage has move approximately 1 volt. That fits within your 0.05 volts per day. Thanks to everyone. Lots of interesting and helpful information. Chris Howard ___ 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. ___ 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.
Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion)
Bob Camp wrote: Hi If you have one of the 10811's out of a Z3801, then it's EFC range is ~ 10X a normal part. There apparently are other odd EFC ranges out there. Bob For example, the 5071A cesium standard has 10X range (modified 10811). I guess in the 5061 you just had to tweak the mechanical trimmer occasionally if the xtal osc drifted out of range. With all the other maintenance on the '61, this didn't seem like much of an additional burden. We wanted to make the 5071A automatic and convinced ourselves we could get away with increasing the EFC range. There were two issues with this: one was the possible lower Q of a hyperabrupt varactor. We determined that there was nothing risky about hyperabrupt diodes. The other issue was contamination due to either the 10811's internal Zener reference or the external DAC. The Zener reference diode, according to the designers, is a low noise Zener (I don't know if it is the buried type), but anyway, it is a legacy part, but a known good legacy part. The 5071A DAC was a very carefully designed one that was good enough. Rick Karlquist N6RK ___ 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.
Re: [time-nuts] getting a grip on 10811 drift (beginner-ishquestion)
I have three 5071 10811's all have below 1 E-12 AV from 1 to 100 seconds. Bert Kehren In a message dated 11/5/2012 7:07:52 P.M. Eastern Standard Time, rich...@karlquist.com writes: Bob Camp wrote: Hi If you have one of the 10811's out of a Z3801, then it's EFC range is ~ 10X a normal part. There apparently are other odd EFC ranges out there. Bob For example, the 5071A cesium standard has 10X range (modified 10811). I guess in the 5061 you just had to tweak the mechanical trimmer occasionally if the xtal osc drifted out of range. With all the other maintenance on the '61, this didn't seem like much of an additional burden. We wanted to make the 5071A automatic and convinced ourselves we could get away with increasing the EFC range. There were two issues with this: one was the possible lower Q of a hyperabrupt varactor. We determined that there was nothing risky about hyperabrupt diodes. The other issue was contamination due to either the 10811's internal Zener reference or the external DAC. The Zener reference diode, according to the designers, is a low noise Zener (I don't know if it is the buried type), but anyway, it is a legacy part, but a known good legacy part. The 5071A DAC was a very carefully designed one that was good enough. Rick Karlquist N6RK ___ 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. ___ 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.
