Re: [time-nuts] T.I. experimenting - newbie question
Both units give slightly different readings between the internal timebase and my GPSDO (Z3801A). The older unit gives the most consistent + + and - - readings using its timebase (difference is in the tens of ps with 10 sec averaging). Joe Gray W5JG On Mon, Apr 4, 2011 at 11:36 PM, bownes wrote: > Another interesting measurement would be to use the timebase output and > external reference to compare the readings using the same timebase. > > Or are you already using a gpsdo? > ___ 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] T.I. experimenting - newbie question
Another interesting measurement would be to use the timebase output and external reference to compare the readings using the same timebase. Or are you already using a gpsdo? On Apr 5, 2011, at 12:08 AM, Joseph Gray wrote: > I'm keeping the "newbie question" in the subject for those who wish to > ignore this thread. To those who respond, your contribution to the > diminution of my ignorance is appreciated :-) > > I had borrowed two different 5328A counters. I just compared them, > using the exact same coax, connectors and settings. Both units were > warmed up for over one hour. > > In my previous readings, I was averaging for 1 s and rounding to one > decimal place. The following readings are averaged for 10 s and > rounded to two decimal places. This seemed like a good place to round, > as the readings were stable enough to this point. > > Old 5328A (slide power switch): > + + = 19.43 ns > - - = 19.49 ns > > Newer 5328A (toggle power switch): > + + = 18.92 ns > - - = 19.41 ns > > The A and B inputs on the old unit match much more closely. If I > average the readings of each unit, there is more than 200 ps > difference between the old and new unit. How do I know which one is > correct? > > Joe Gray > W5JG > > On Mon, Apr 4, 2011 at 8:25 PM, Joseph Gray wrote: >> Hal, >> >> Here are the results I got using your suggestion. The numbers may be a >> bit different than last night as I'm not sure I'm using the same >> cable. >> >> A+, B+ = 18.9 ns >> A-, B- = 19.4 ns >> >> Obviously there is some difference in delay between the A and B >> channels. Otherwise, the two numbers would have been identical - >> correct? >> >> If I take the average of the two readings, I get 19.05 ns, which is >> more precise than the readings I'm taking. I'm rounding to the nearest >> 0.1 ns on the readings. >> >> A+, B- = 5014.6 ns >> A-, B+ = 5023.5 ns >> >> If I take the average of these two readings and subtract out the 5 us >> for 1/2 period of the 100 KHz square wave, if get 19.15 ns. This >> agrees very closely with the above average. >> >> I haven't looked at the service manual for the 5328A yet, so I don't >> know if I even have the proper equipment to attempt a calibration. In >> the mean time, would you say that taking the average of the first two >> readings is a valid method? >> >> Joe Gray >> W5JG >> >> On Sun, Apr 3, 2011 at 7:18 PM, Hal Murray wrote: >>> >>> How about a square wave? Start on one edge, stop on the next cycle. >>> >>> You can play with start on rising edge, stop on falling and the reverse. >>> They should add up to the total. >> > > ___ > 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] T.I. experimenting - newbie question
Hal, replies inline. On Mon, Apr 4, 2011 at 10:21 PM, Hal Murray wrote: > >> Here are the results I got using your suggestion. The numbers may be a bit >> different than last night as I'm not sure I'm using the same cable. > >> A+, B+ = 18.9 ns >> A-, B- = 19.4 ns >> Obviously there is some difference in delay between the A and B channels. >> Otherwise, the two numbers would have been identical - correct? > ... >> If I take the average of the two readings, I get 19.05 ns, which is more >> precise than the readings I'm taking. I'm rounding to the nearest 0.1 ns on >> the readings. > > There are several possibilities for asymmetry. > The input signal could have other than a 50/50 high/low ratio. > The trigger levels could be set at other than the half-way point. See my reply to John about trigger levels. > Do you have a scope? Yes, I will dig out the scope and check. The last time I checked the Spectracom 8140 (long ago), it was ok. I'll check it again. > There are probably second order problems with different rise/fall times. > > >> A+, B- = 5014.6 ns >> A-, B+ = 5023.5 ns >> If I take the average of these two readings and subtract out the 5 us for >> 1/2 period of the 100 KHz square wave, if get 19.15 ns. This agrees >> very closely with the above average. > > I read that as everything mostly works. That was my assumption, but it's nice to have someone more knowledgeable confirm it. > The question is how well does it work and/or what can you do to get > more/better data? > > You can get another set of numbers by swapping the A and B inputs so the > signal goes from B to A rather than A to B. > > Some of the errors might be more obvious if you deliberately offset the > trigger levels. > > NB: That's for all 4 modes: > A+ to B+ will be slightly less than a whole cycle. > A+ to B- will be slightly less than a 1/2 cycle. I'll try swapping inputs and see what happens. I'm not sure if I'll get to this tonight. If not, tomorrow night. Joe Gray W5JG ___ 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] T.I. experimenting - newbie question
John, Yes, they both do. However, only one has the DVM option that lets me measure the voltage trigger levels. When I turned off preset and set the levels manually to match, I got similar numbers to using preset. On Mon, Apr 4, 2011 at 10:13 PM, J. Forster wrote: > Does the counter have setable input threasholds? Most do. Are they set the > the same? > > -John ___ 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] T.I. experimenting - newbie question
> Here are the results I got using your suggestion. The numbers may be a bit > different than last night as I'm not sure I'm using the same cable. > A+, B+ = 18.9 ns > A-, B- = 19.4 ns > Obviously there is some difference in delay between the A and B channels. > Otherwise, the two numbers would have been identical - correct? ... > If I take the average of the two readings, I get 19.05 ns, which is more > precise than the readings I'm taking. I'm rounding to the nearest 0.1 ns on > the readings. There are several possibilities for asymmetry. The input signal could have other than a 50/50 high/low ratio. The trigger levels could be set at other than the half-way point. Do you have a scope? There are probably second order problems with different rise/fall times. > A+, B- = 5014.6 ns > A-, B+ = 5023.5 ns > If I take the average of these two readings and subtract out the 5 us for > 1/2 period of the 100 KHz square wave, if get 19.15 ns. This agrees > very closely with the above average. I read that as everything mostly works. The question is how well does it work and/or what can you do to get more/better data? You can get another set of numbers by swapping the A and B inputs so the signal goes from B to A rather than A to B. Some of the errors might be more obvious if you deliberately offset the trigger levels. NB: That's for all 4 modes: A+ to B+ will be slightly less than a whole cycle. A+ to B- will be slightly less than a 1/2 cycle. ... -- These are my opinions, not necessarily my employer's. 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.
Re: [time-nuts] T.I. experimenting - newbie question
Does the counter have setable input threasholds? Most do. Are they set the the same? -John > I'm keeping the "newbie question" in the subject for those who wish to > ignore this thread. To those who respond, your contribution to the > diminution of my ignorance is appreciated :-) > > I had borrowed two different 5328A counters. I just compared them, > using the exact same coax, connectors and settings. Both units were > warmed up for over one hour. > > In my previous readings, I was averaging for 1 s and rounding to one > decimal place. The following readings are averaged for 10 s and > rounded to two decimal places. This seemed like a good place to round, > as the readings were stable enough to this point. > > Old 5328A (slide power switch): > + + = 19.43 ns > - - = 19.49 ns > > Newer 5328A (toggle power switch): > + + = 18.92 ns > - - = 19.41 ns > > The A and B inputs on the old unit match much more closely. If I > average the readings of each unit, there is more than 200 ps > difference between the old and new unit. How do I know which one is > correct? > > Joe Gray > W5JG > > On Mon, Apr 4, 2011 at 8:25 PM, Joseph Gray wrote: >> Hal, >> >> Here are the results I got using your suggestion. The numbers may be a >> bit different than last night as I'm not sure I'm using the same >> cable. >> >> A+, B+ = 18.9 ns >> A-, B- = 19.4 ns >> >> Obviously there is some difference in delay between the A and B >> channels. Otherwise, the two numbers would have been identical - >> correct? >> >> If I take the average of the two readings, I get 19.05 ns, which is >> more precise than the readings I'm taking. I'm rounding to the nearest >> 0.1 ns on the readings. >> >> A+, B- = 5014.6 ns >> A-, B+ = 5023.5 ns >> >> If I take the average of these two readings and subtract out the 5 us >> for 1/2 period of the 100 KHz square wave, if get 19.15 ns. This >> agrees very closely with the above average. >> >> I haven't looked at the service manual for the 5328A yet, so I don't >> know if I even have the proper equipment to attempt a calibration. In >> the mean time, would you say that taking the average of the first two >> readings is a valid method? >> >> Joe Gray >> W5JG >> >> On Sun, Apr 3, 2011 at 7:18 PM, Hal Murray >> wrote: >>> >>> How about a square wave? Start on one edge, stop on the next cycle. >>> >>> You can play with start on rising edge, stop on falling and the >>> reverse. >>> They should add up to the total. >> > > ___ > 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] T.I. experimenting - newbie question
I'm keeping the "newbie question" in the subject for those who wish to ignore this thread. To those who respond, your contribution to the diminution of my ignorance is appreciated :-) I had borrowed two different 5328A counters. I just compared them, using the exact same coax, connectors and settings. Both units were warmed up for over one hour. In my previous readings, I was averaging for 1 s and rounding to one decimal place. The following readings are averaged for 10 s and rounded to two decimal places. This seemed like a good place to round, as the readings were stable enough to this point. Old 5328A (slide power switch): + + = 19.43 ns - - = 19.49 ns Newer 5328A (toggle power switch): + + = 18.92 ns - - = 19.41 ns The A and B inputs on the old unit match much more closely. If I average the readings of each unit, there is more than 200 ps difference between the old and new unit. How do I know which one is correct? Joe Gray W5JG On Mon, Apr 4, 2011 at 8:25 PM, Joseph Gray wrote: > Hal, > > Here are the results I got using your suggestion. The numbers may be a > bit different than last night as I'm not sure I'm using the same > cable. > > A+, B+ = 18.9 ns > A-, B- = 19.4 ns > > Obviously there is some difference in delay between the A and B > channels. Otherwise, the two numbers would have been identical - > correct? > > If I take the average of the two readings, I get 19.05 ns, which is > more precise than the readings I'm taking. I'm rounding to the nearest > 0.1 ns on the readings. > > A+, B- = 5014.6 ns > A-, B+ = 5023.5 ns > > If I take the average of these two readings and subtract out the 5 us > for 1/2 period of the 100 KHz square wave, if get 19.15 ns. This > agrees very closely with the above average. > > I haven't looked at the service manual for the 5328A yet, so I don't > know if I even have the proper equipment to attempt a calibration. In > the mean time, would you say that taking the average of the first two > readings is a valid method? > > Joe Gray > W5JG > > On Sun, Apr 3, 2011 at 7:18 PM, Hal Murray wrote: >> >> How about a square wave? Start on one edge, stop on the next cycle. >> >> You can play with start on rising edge, stop on falling and the reverse. >> They should add up to the total. > ___ 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] GPS antenna with direction orientation?
> Original Message > Subject: Re: [time-nuts] GPS antenna with direction orientation? > From:"Tom Van Baak" > Date:Sun, April 3, 2011 6:58 pm > To: "Discussion of precise time and frequency measurement" > > -- > >> A couple of years ago I picked up a surplus Aeroantenna choke-ring GPS >> antenna that I think was intended for surveying use. I finally got it >> installed today and noticed that it has an arrow on the bottom >> indicating that the antenna should be oriented with the arrow facing north. >> >> I'm trying to figure out why an omnidirectional antenna should care >> about which way it is oriented. The best I can figure is that perhaps >> it is for repeatability in surveying, so that any minor offset in the >> phase center would remain consistent when moving the antenna from site >> to site. >> >> Does anyone have a better answer? >> >> John > > That's my understanding too. Interpret the word "omnidirectional" > like the words "cable length"; to a first approximation it is obvious > and very constant, no worries; but if you look too many decimal > places to the right, well of course, you will see variations. > > My Leica/Novatel/Areoantenna575 and Ashtech L1/L2 antennas > have the same arrow. I pointed mine north only by eyeball. My > hunch was that at this extreme level issues like cable tempco or > receiver temperature were more important so I used FSJ1 heliax > for the feed and kept the lab stable to 1C. I never revisited the > angle issue. > > To be certain, and if your gear is sensitive enough, you can do > an experiment and plot the phase center variation as a function > of antenna angle. But given how the GPS constellation changes > over time I think it would take many weeks before you could get > results. I'd guess the asymmetry is well below 1 ns. If you have > a spare ham antenna rotor then vary the angle over 360 degrees > every N hours and then after you've collected many days of data > look carefully for correlation between gps phase and antenna > angle right around tau N hours. > > BTW, I gave up I gave up on this sort of problem when I realized > that plate tectonics (mm to cm per year here in the NW) and local > earthquakes had a greater effect on my long-term timing. See: > http://www.leapsecond.com/pages/quake/ > > If there are any cm-level surveyors on the list I'd like to hear their > experience in the matter. I could imagine John's question has an > effect only at the mm level, but not cm or meter level. > > /tvb Correct. The choke rings have practically perfect cylindrical symmetry about the (vertical) axis of the antenna, but the feed -- at the center of the choke rings, and hidden by a radome -- does not. The reason for orienting the antenna consistently in azimuth is to improve the reproducibility of position determinations. By design and construction, some antennas are more symmetrical than others. I was a millimeter-level surveyor. My own relative-position determinations were reproducible within less than 1 mm in both horizontal coordinates and within 1 to 2 mm in the vertical, even when the determination was repeated months later, with different antennas, different receivers, different operators, and different data-processors; but I _never_ bothered with azimuthal alignment of my antennas because, by design and construction, they were azimuthally symmetrical within less than 1 mm. Most geodetic surveyors bought inferior antennas because they were cheaper. The symmetry of an antenna is best measured at a test range where the antenna can be rotated while receiving a signal from a fixed source. The antenna must be rotated both in azimuth and in elevation. Ideally, far-field wave-fronts are spheres centered on an identifiable point fixed with respect to the antenna's mount, and this point is the same for each GPS signal band. The main reason for departure from spherical symmetry is usually that the antenna responds to signals arriving from below, after reflection from the ground, in addition to signals arriving directly from a satellite in the sky. Any antenna having finite size will have non-zero response below horizontal. This result follows from physical optics, in other words wave diffraction. Larger antennas are intrinsically advantaged; but they are heavier, harder to handle, and more expensive. See above regarding what most surveyors buy. >From a friend, -John == ___ 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] T.I. experimenting - newbie question
Hal, Here are the results I got using your suggestion. The numbers may be a bit different than last night as I'm not sure I'm using the same cable. A+, B+ = 18.9 ns A-, B- = 19.4 ns Obviously there is some difference in delay between the A and B channels. Otherwise, the two numbers would have been identical - correct? If I take the average of the two readings, I get 19.05 ns, which is more precise than the readings I'm taking. I'm rounding to the nearest 0.1 ns on the readings. A+, B- = 5014.6 ns A-, B+ = 5023.5 ns If I take the average of these two readings and subtract out the 5 us for 1/2 period of the 100 KHz square wave, if get 19.15 ns. This agrees very closely with the above average. I haven't looked at the service manual for the 5328A yet, so I don't know if I even have the proper equipment to attempt a calibration. In the mean time, would you say that taking the average of the first two readings is a valid method? Joe Gray W5JG On Sun, Apr 3, 2011 at 7:18 PM, Hal Murray wrote: > > How about a square wave? Start on one edge, stop on the next cycle. > > You can play with start on rising edge, stop on falling and the reverse. > They should add up to the total. ___ 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] HP 3586 entirely referenced to 10MHz: A solution II
On Mon, Apr 04, 2011 at 07:19:38AM -0400, Chuck Harris wrote: > Basically, the higher the division ratio in a PLL synthesizer, > which is what you are describing, the greater the phase noise. No question about that, indeed. But I am talking about a very low bandwidth loop (presumably well under 1 HZ should work) which means the phase noise contribution from the dividers and reference should be only inside that 1 Hz bandpass. Outside of that the original crystal oscillator phase noise should control, and while this won't improve that it also won't make it any worse. > > You can think of it this way: Both the reference, and the oscillator > being controlled, need to be divided down to some common frequency > that you feed to the phase detector. The entire time the counter is > counting up the cycles to get you a cycle of that common frequency, > the oscillator is not being disciplined. It is only after the > count gets done that the phase detector can compare the two signals > and create a correction correct for the error in the oscillator. True, but I am pretty sure the original crystal oscillator (even modified with a varactor for tuning) was not phase-noisier than the rest of the instruments LOs. It is, after all, a LF crystal oscillator running at 13 or 17 KHz with presumably a high Q crystal which shouldn't to the first order have unreasonable phase noise in the band around it. The original problem was that this oscillator was not locked to a reference and could drift a few tenths of a HZ (and maybe even Hz) randomly with temp - not that it had too much phase noise. > > The DDS is essentially a hardware solution to finding a suitable > divider ratio to convert one frequency into another. I do understand DDSes. > > -Chuck Harris -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 "An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either." ___ 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] GPS antenna with direction orientation?
On 04/04/2011 02:42 AM, John Ackermann N8UR wrote: A couple of years ago I picked up a surplus Aeroantenna choke-ring GPS antenna that I think was intended for surveying use. I finally got it installed today and noticed that it has an arrow on the bottom indicating that the antenna should be oriented with the arrow facing north. I'm trying to figure out why an omnidirectional antenna should care about which way it is oriented. The best I can figure is that perhaps it is for repeatability in surveying, so that any minor offset in the phase center would remain consistent when moving the antenna from site to site. Does anyone have a better answer? Since the phase-center is not completely stable with relation to direction, the antennas needs to be oriented in such a fashion that the corrections can be applied. It's routinely used in precision measurements such as the various reference networks. The calibration files exists for known antennas, so then identifying the antenna would allow for the correct calibration file to be used. So it boils down to turning the antenna so the arrow points north. Cheers, Magnus ___ 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] Tbolt temperature question
On Mon, Apr 4, 2011 at 9:50 AM, msproul wrote: > > What is the normally expected oven temperature range of the Thunderbolt? > > Over the past year the temperature of my Tbolt, as reported by Lady Heather, > has slowly increased from the low 40"s C to the high 40"s. The maximum > temperature has now crept up to 50 C and is shown today at 50.8 C. At 50 C Is the temperature sensor accurate? I always suspect the instrumentation until it's verified. My understanding of oxco is that the crystal needs to be at a very specify temperature where there is a "bump" on the graph such that slope is near horizontal. Seems like there is drift in some component -- = Chris Albertson Redondo Beach, California ___ 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] Tbolt temperature question
> What is the normally expected oven temperature range of the Thunderbolt? > Over the past year the temperature of my Tbolt, as reported by Lady Heather, > has slowly increased from the low 40"s C to the high 40"s. The maximum > temperature has now crept up to 50 C and is shown today at 50.8 C. That's not the oven temperature. It's the temperature at the far corner of the board which might be a good indication of the environmental temperature. Has your local temperature changed? Have you been piling stuff on top of your TBolt to block the air flow, or adding warm stuff underneath it? -- These are my opinions, not necessarily my employer's. 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.
Re: [time-nuts] Tbolt temperature question
Mine runs 36-37 degrees. On Mon, Apr 4, 2011 at 12:50 PM, msproul wrote: > > What is the normally expected oven temperature range of the Thunderbolt? > > Over the past year the temperature of my Tbolt, as reported by Lady > Heather, > has slowly increased from the low 40"s C to the high 40"s. The maximum > temperature has now crept up to 50 C and is shown today at 50.8 C. At 50 C > the LH > temperature display changes from white to yellow which suggests a warning. > All other parameters appear to be normal. > > Does the 50.8 C indicate a potential problem? Is something failing? What is > the > maximum temperature that should be expected? > > Thanks for any help. > > Maury > > ___ > 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] Tbolt temperature question
Mine typically runs in the low to mid 30 deg C range. ___ 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] Tbolt temperature question
Maury-- Mine hovers around 36 degrees C +/- about 1.5 degrees C. Given the time, I'm going to start working with LH's active temperature control, and will be looking to settle on something between 34 and 38 degrees C, at least that's my current guess. Over 45 definitely seems warm to me! bob k6rtm in sunny silicon valley -- Message: 6 Date: Mon, 4 Apr 2011 11:50:55 -0500 From: msproul To: time-nuts@febo.com Subject: [time-nuts] Tbolt temperature question Message-ID: Content-Type: text/plain; charset="us-ascii" ; format="flowed" What is the normally expected oven temperature range of the Thunderbolt? Over the past year the temperature of my Tbolt, as reported by Lady Heather, has slowly increased from the low 40"s C to the high 40"s. The maximum temperature has now crept up to 50 C and is shown today at 50.8 C. At 50 C the LH temperature display changes from white to yellow which suggests a warning. All other parameters appear to be normal. Does the 50.8 C indicate a potential problem? Is something failing? What is the maximum temperature that should be expected? Thanks for any help. Maury -- ___ 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] Tbolt temperature question
On Mon, Apr 04, 2011 at 11:50:55AM -0500, msproul wrote: > What is the normally expected oven temperature range of the Thunderbolt? I generally see mine run at 33-40 C depending on the ambient temperature of the room. What's the temperature of the environment it's in? It's going to try and keep temperature stable, and to do that, it needs to be above the ambient temp. --msa ___ 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] Tbolt temperature question
What is the normally expected oven temperature range of the Thunderbolt? Over the past year the temperature of my Tbolt, as reported by Lady Heather, has slowly increased from the low 40"s C to the high 40"s. The maximum temperature has now crept up to 50 C and is shown today at 50.8 C. At 50 C the LH temperature display changes from white to yellow which suggests a warning. All other parameters appear to be normal. Does the 50.8 C indicate a potential problem? Is something failing? What is the maximum temperature that should be expected? Thanks for any help. Maury ___ 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] HP 3586 entirely referenced to 10MHz: A solution II
Hello Didier; I don't have a copy of the schematic however I was wondering if there are trim caps installed for these crystals?? If so, then a varactor can tune above and below in place of the mechanical cap if you remove it. Undoubtedly there is some loading cap in the circuit that could be tweaked a tad. Crystals drift over time though, this could have an effect on this concept. It may be that they have already drifted too far to tweak with the VCO concept. Also, there are many ways that a PLL ideas interact with phase noise. If the PLL reference source is quieter than the intrinsic noise of the VCO then the loop band width does govern the close in noise spectrum. However, there are many systems wherein the reference bandwidth is very small and the VCO noise governsl. Take for instance the PPS control of the GPSDO OXCO. The PPS frequency reference is unable to reduce the noise of the OXCO above about one half Hz, so the ultimate phase noise above that frequency is that of the oscillator itself. This can be a creative brain buster when working on designs for these ideas. My vote is to do a DDS synthesizer, this is a fine evolution low in cost and easy to implement, to displace approximate oscillators. What frequencies are you generating? Regards; Greg On 4/4/2011 7:29 AM, Chuck Harris wrote: Hi Didier, If you want to convert the Xtal to a VCO, you will have to adjust the parallel capacitance so that the crystal can get above the desired frequency, and then design the varactor circuit so that it can pull from there to below the desired frequency...which should be possible if the crystal was capable of being tuned on frequency. The crystal might be high enough Q to run in a PLL with a very high division ratio, but I would still expect it to hiccup around about the period of the divider but as you say, it might not matter. The DDS works out to be such a simple solution, I think the minuscule offset is hardly worth getting worked up over. -Chuck shali...@gmail.com wrote: "Basically, the higher the division ratio in a PLL synthesizer, which is what you are describing, the greater the phase noise." In that case, that may not be a problem. Since the oscillator is a crystal, phase noise should be low enough. One other issue is that most crystals only want to move in one direction (with the varactor pulling trick), so if it is on the wrong side of where you want it, that won't work. Otherwise, I have been thinking about that myself. Didier KO4BB ___ 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] HP 3586 entirely referenced to 10MHz: A solution II
Hi Didier, If you want to convert the Xtal to a VCO, you will have to adjust the parallel capacitance so that the crystal can get above the desired frequency, and then design the varactor circuit so that it can pull from there to below the desired frequency...which should be possible if the crystal was capable of being tuned on frequency. The crystal might be high enough Q to run in a PLL with a very high division ratio, but I would still expect it to hiccup around about the period of the divider but as you say, it might not matter. The DDS works out to be such a simple solution, I think the minuscule offset is hardly worth getting worked up over. -Chuck shali...@gmail.com wrote: "Basically, the higher the division ratio in a PLL synthesizer, which is what you are describing, the greater the phase noise." In that case, that may not be a problem. Since the oscillator is a crystal, phase noise should be low enough. One other issue is that most crystals only want to move in one direction (with the varactor pulling trick), so if it is on the wrong side of where you want it, that won't work. Otherwise, I have been thinking about that myself. Didier KO4BB ___ 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] GPS antenna with direction orientation?
Maybe it's not truely omnidirectional? Maybe like a cardioid pattern? Didier KO4BB --Original Message-- From: John Ackermann N8UR Sender: time-nuts-boun...@febo.com To: Time-Nuts ReplyTo: Time-Nuts Subject: [time-nuts] GPS antenna with direction orientation? Sent: Apr 3, 2011 7:42 PM A couple of years ago I picked up a surplus Aeroantenna choke-ring GPS antenna that I think was intended for surveying use. I finally got it installed today and noticed that it has an arrow on the bottom indicating that the antenna should be oriented with the arrow facing north. I'm trying to figure out why an omnidirectional antenna should care about which way it is oriented. The best I can figure is that perhaps it is for repeatability in surveying, so that any minor offset in the phase center would remain consistent when moving the antenna from site to site. Does anyone have a better answer? John ___ 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. Sent from my BlackBerry Wireless thingy while I do other things... ___ 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] HP 3586 entirely referenced to 10MHz: A solution II
"Basically, the higher the division ratio in a PLL synthesizer, which is what you are describing, the greater the phase noise." In that case, that may not be a problem. Since the oscillator is a crystal, phase noise should be low enough. One other issue is that most crystals only want to move in one direction (with the varactor pulling trick), so if it is on the wrong side of where you want it, that won't work. Otherwise, I have been thinking about that myself. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Chuck Harris Sender: time-nuts-boun...@febo.com Date: Mon, 04 Apr 2011 07:19:38 To: Discussion of precise time and frequency measurement Reply-To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 3586 entirely referenced to 10MHz: A solution II Basically, the higher the division ratio in a PLL synthesizer, which is what you are describing, the greater the phase noise. You can think of it this way: Both the reference, and the oscillator being controlled, need to be divided down to some common frequency that you feed to the phase detector. The entire time the counter is counting up the cycles to get you a cycle of that common frequency, the oscillator is not being disciplined. It is only after the count gets done that the phase detector can compare the two signals and create a correction correct for the error in the oscillator. The DDS is essentially a hardware solution to finding a suitable divider ratio to convert one frequency into another. -Chuck Harris David I. Emery wrote: > On Mon, Apr 04, 2011 at 02:00:14AM -0400, David I. Emery wrote: >> On Sat, Apr 02, 2011 at 04:13:55PM -0400, Chuck Harris wrote: >> >>> Unlike simply stabilizing the BFO crystal as you propose. >> >> Has anyone given any thought to an alternative - phase locking >> the original BFO Xtals with a very narrow bandwidth loop to something >> derived from the 10 Mhz standard in such a way that the final frequency >> of the BFO comes out exact ? Looks to me (superficially without looking >> at the schematic carefully) like this might be possible too... > > To elaborate a tiny bit, if you divide 10 MHz to 25 HZ you could > use that as the reference for a classic PLL loop that stabilized the > crystals with a varactor... provided of course suitable low pass > filtering was used. There are also approaches involving doing early > late sampling of the BFOs on selected edges of the 10 MHz clock which > could be done more digitally in a FPGA. > > I presume one can pull the existing crystals enough with some hacking > of the oscillator to add a varactor... > > This would avoid a non integer frequency setting where the DDS > approach does not (unless you multiply by 3 to 30 MHz first I think). > > > ___ 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] T.I. experimenting - newbie question
You cannot change impedance without changing geometry or dielectric, and any of these changes will affect vop. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Joseph Gray Sender: time-nuts-boun...@febo.com Date: Sun, 3 Apr 2011 16:37:05 To: Discussion of precise time and frequency measurement Reply-To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] T.I. experimenting - newbie question I assume you mean that impedance has an effect on VOP? Can you point to any internet sources that explain this effect? Preferably something not overly technical. Joe Gray W5JG On Sun, Apr 3, 2011 at 4:11 PM, paul swed wrote: > It does change vop ___ 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] GPS antenna with direction orientation?
Hi Brooke, > Hi John: > > Exactly. There are about a dozen specific antennas that have been > thoroughly characterized for phase center at L1 and L2. I think to the > mm level. > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > There are a lot more than a dozen antennas that are characterized. See http://www.ngs.noaa.gov/ANTCAL/index.shtml for the small list. A larger number of calibrations are available from Geo++ http://geopp.de/index.php?bereich=5&kategorie=34&artikel=62 but the data from Geo++ is not for free. Your postprocessing software might already have some of the Geo++ data. Note that NGS normaly give Relative corrections (compared with the "golden standard" an AOA JPL chokering iirc) Geo++ often give absolute corrections. -- Björn ___ 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] HP 3586 entirely referenced to 10MHz: A solution II
Basically, the higher the division ratio in a PLL synthesizer, which is what you are describing, the greater the phase noise. You can think of it this way: Both the reference, and the oscillator being controlled, need to be divided down to some common frequency that you feed to the phase detector. The entire time the counter is counting up the cycles to get you a cycle of that common frequency, the oscillator is not being disciplined. It is only after the count gets done that the phase detector can compare the two signals and create a correction correct for the error in the oscillator. The DDS is essentially a hardware solution to finding a suitable divider ratio to convert one frequency into another. -Chuck Harris David I. Emery wrote: On Mon, Apr 04, 2011 at 02:00:14AM -0400, David I. Emery wrote: On Sat, Apr 02, 2011 at 04:13:55PM -0400, Chuck Harris wrote: Unlike simply stabilizing the BFO crystal as you propose. Has anyone given any thought to an alternative - phase locking the original BFO Xtals with a very narrow bandwidth loop to something derived from the 10 Mhz standard in such a way that the final frequency of the BFO comes out exact ? Looks to me (superficially without looking at the schematic carefully) like this might be possible too... To elaborate a tiny bit, if you divide 10 MHz to 25 HZ you could use that as the reference for a classic PLL loop that stabilized the crystals with a varactor... provided of course suitable low pass filtering was used. There are also approaches involving doing early late sampling of the BFOs on selected edges of the 10 MHz clock which could be done more digitally in a FPGA. I presume one can pull the existing crystals enough with some hacking of the oscillator to add a varactor... This would avoid a non integer frequency setting where the DDS approach does not (unless you multiply by 3 to 30 MHz first I think). ___ 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] GPS antenna with direction orientation?
> A couple of years ago I picked up a surplus Aeroantenna choke-ring GPS > antenna that I think was intended for surveying use. I finally got it > installed today and noticed that it has an arrow on the bottom > indicating that the antenna should be oriented with the arrow facing > north. Most surveying antennas intended for static use has an "North" arrow or are implicitly supposed to aligh the "connector" towards north. > I'm trying to figure out why an omnidirectional antenna should care > about which way it is oriented. The best I can figure is that perhaps > it is for repeatability in surveying, so that any minor offset in the > phase center would remain consistent when moving the antenna from site > to site. > > Does anyone have a better answer? You are right! I have a few chokerings with different antenna elements than the one show in the below url: http://www.ngs.noaa.gov/cgi-bin/query_cal_antennas.prl?Model=AER&Antenna=AERAT2775_43 If you look at the numbers below 2.3 -.6 88.3(L1) -.2.2 94.1(L2) They are the x,y and z phase center offsets for L1 an L2 respectively. For this antenna. The other numbers are corrections based on angle of arrival to the antenna. Nothing is really fully symmetric if you look closely enough. The antenna calibration data is used by postprocessing GNSS software packages. -- Björn ___ 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] Help needed in Seattle with HP 8620C and 86242D Sweep Oscilla...
Pete, contact me direct, I am in Miami but I may be able to talk you through it. If you do it to sell, check prices first, they do not get much money now a days. I did recently salvaged some. Bert In a message dated 4/4/2011 12:57:54 A.M. Eastern Daylight Time, pet...@standingwave.org writes: Hello! I've got a HP 8620C with a 86242D plugin (5.9 - 9.0GHz) that is in very good physical condition. The machine powers up, and I can get a sawtooth wave from the sweep out connector. The top row of knobs move the pointers in the window as they should. I don't have a network analyzer (or even a high frequency counter) so I cannot really tell if this thing is working. I am intending on getting information on the operation function of the oscillator and then selling it If there is anybody on the list in the Seattle with the knowledge and equipment to help me check out this machine I will be happy to pay for your time. Please contact me off list. Thanks! Pete Issaquah, WA ___ 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] HP 3586 entirely referenced to 10MHz: A solution II
On Mon, Apr 04, 2011 at 02:00:14AM -0400, David I. Emery wrote: > On Sat, Apr 02, 2011 at 04:13:55PM -0400, Chuck Harris wrote: > > > Unlike simply stabilizing the BFO crystal as you propose. > > Has anyone given any thought to an alternative - phase locking > the original BFO Xtals with a very narrow bandwidth loop to something > derived from the 10 Mhz standard in such a way that the final frequency > of the BFO comes out exact ? Looks to me (superficially without looking > at the schematic carefully) like this might be possible too... To elaborate a tiny bit, if you divide 10 MHz to 25 HZ you could use that as the reference for a classic PLL loop that stabilized the crystals with a varactor... provided of course suitable low pass filtering was used. There are also approaches involving doing early late sampling of the BFOs on selected edges of the 10 MHz clock which could be done more digitally in a FPGA. I presume one can pull the existing crystals enough with some hacking of the oscillator to add a varactor... This would avoid a non integer frequency setting where the DDS approach does not (unless you multiply by 3 to 30 MHz first I think). -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 "An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either." ___ 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.
