[time-nuts] FMT on PC
I've been away from the group for a while but I rejoined with a couple of questions. Hope they haven't been beaten to death already. I want to set up a FMT on an old PC using GPS. Its for ham mesh network and it will not be connected to the internet. I found a couple of sites and they seem to be dated. And unclear how to integrate the GPS in. Ideally I would like to use the thuderbolt I have running for my 10 Mhz reference but I do have other GPS devices with NEMA out put. Any links? Suggestions? Thanks N3IZN ___ 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] [FMT-nuts] LightSquared is Toast!!
See: http://www.nytimes.com/2012/02/15/business/media/fcc-bars-airwave-use-for-broadband-plan.html?_r=1scp=3sq=lightsquaredst=cse On 15 February 2012 14:34, David McClain d...@refined-audiometrics.comwrote: Yeaaa! LightSquared GPS-band broadband is gone. Big article on the front page of the NYTimes Business section. Dr. David McClain, de N7AIG d...@refined-audiometrics.com __._,_.___ Your email settings: Individual Email|Traditional Change settings via the Webhttp://groups.yahoo.com/group/FMT-nuts/join;_ylc=X3oDMTJncTZvaHZlBF9TAzk3NDc2NTkwBGdycElkAzE5ODg1OTU3BGdycHNwSWQDMTcwNTA4MzI5MQRzZWMDZnRyBHNsawNzdG5ncwRzdGltZQMxMzI5MzE2NDQ5(Yahoo! ID required) Change settings via email: Switch delivery to Daily Digestfmt-nuts-dig...@yahoogroups.com?subject=Email+Delivery:+Digest| Switch to Fully Featuredfmt-nuts-fullfeatu...@yahoogroups.com?subject=Change+Delivery+Format:+Fully+Featured Visit Your Group http://groups.yahoo.com/group/FMT-nuts;_ylc=X3oDMTJlMzZmMnFmBF9TAzk3NDc2NTkwBGdycElkAzE5ODg1OTU3BGdycHNwSWQDMTcwNTA4MzI5MQRzZWMDZnRyBHNsawNocGYEc3RpbWUDMTMyOTMxNjQ0OQ--| Yahoo! Groups Terms of Use http://docs.yahoo.com/info/terms/ | Unsubscribe fmt-nuts-unsubscr...@yahoogroups.com?subject=Unsubscribe __,_._,___ ___ 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] [FMT-nuts] LightSquared is Toast!!
Good news for a change! Rob K -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter Vince Sent: 15 February 2012 15:16 To: fmt-n...@yahoogroups.com Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] [FMT-nuts] LightSquared is Toast!! See: http://www.nytimes.com/2012/02/15/business/media/fcc-bars-airwave-use-for-br oadband-plan.html?_r=1scp=3sq=lightsquaredst=cse On 15 February 2012 14:34, David McClain d...@refined-audiometrics.comwrote: Yeaaa! LightSquared GPS-band broadband is gone. Big article on the front page of the NYTimes Business section. Dr. David McClain, de N7AIG d...@refined-audiometrics.com __._,_.___ Your email settings: Individual Email|Traditional Change settings via the Webhttp://groups.yahoo.com/group/FMT-nuts/join;_ylc=X3oDMTJncTZvaHZlB F9TAzk3NDc2NTkwBGdycElkAzE5ODg1OTU3BGdycHNwSWQDMTcwNTA4MzI5MQRzZWMDZnR yBHNsawNzdG5ncwRzdGltZQMxMzI5MzE2NDQ5(Yahoo! ID required) Change settings via email: Switch delivery to Daily Digestfmt-nuts-dig...@yahoogroups.com?subject=Email+Delivery:+Digest | Switch to Fully Featuredfmt-nuts-fullfeatu...@yahoogroups.com?subject=Change+Delivery +Format:+Fully+Featured Visit Your Group http://groups.yahoo.com/group/FMT-nuts;_ylc=X3oDMTJlMzZmMnFmBF9TAzk3NDc2NTk wBGdycElkAzE5ODg1OTU3BGdycHNwSWQDMTcwNTA4MzI5MQRzZWMDZnRyBHNsawNocGYEc3RpbWU DMTMyOTMxNjQ0OQ--| Yahoo! Groups Terms of Use http://docs.yahoo.com/info/terms/ | Unsubscribe fmt-nuts-unsubscr...@yahoogroups.com?subject=Unsubscribe __,_._,___ ___ 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] [FMT-nuts] LightSquared is Toast!!
On 2/15/12 7:16 AM, Peter Vince wrote: See: http://www.nytimes.com/2012/02/15/business/media/fcc-bars-airwave-use-for-broadband-plan.html?_r=1scp=3sq=lightsquaredst=cse Err.. not necessarily. As one of the commentators in the business press said yesterday (paraphrasing).. Harbinger needs to decide whether to shut down LightSquared and take their losses now, or arrange their funds for the legal battles to come. When you have billions riding on the bet, a few million in legal fees (which is tens of thousands of billable hours: a LOT of work) to go to court to get the decision changed isn't always a big problem. As quoted in the lore of Python.. I'm not dead yet... ___ 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I guess it depends on signal to noise ratio. With reciprocal counters, you only need one period to measure as acurately as you need, but to have good acuracy, you need very good S/N, as there is no filtering possible. For example, the HP 5370 can measure a single period of a signal with a resolution of 20pS (excluding noise and trigger imperfections), so excluding these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal with 7 x10-5 precision (if I have not goofed the calculations) More periods improve the resolution proportionately to the quare root. Accuracy is another matter. Didier KO4BB The jitter on a single period is likely very, very high, especially if it comes over the air. That's why one usually measures over a duration of thousands or even millions of periods (effectively called the gate time). The HP 53132A makes something like 200,000 measurements per second. As a result, for a certain range of frequencies, it claims 12 digits/sec of resolution (vs. HP 5370 ~11 digits/sec). /tvb ___ 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Did mounting it on a block of foam help? That is a rather bad solution. You want much softer material to react to quicker things, such as silicon rubber. Also, that would only be a 12 dB/Oct solution. You would really like a few more poles there. The trick is to add weight to the calculation. So you want a very soft material, holding a thick block (lead) and from this base suspend the oscillator through a soft material again. Now you have a 24 dB/Oct solution. The trouble you now will have is that the wires will be another shock/vibration transport mechanism. They would need to be connected to the middle-frame such that outer forces hit the middle weigth and not directly on the sensitive part. They would need to be soft and arranged is such a way that they do not push or pull the inner end, but is allowed to flex alot. Yes, but inserting a chunk of foam is a lot easier than finding a block of lead. It's likely to be good enough. (Make that good enough for most application. This is time-nuts. Nothing is good-enough that somebody won't suggest something better/nuttier. :) Packing bubbles might work too. I'm thinking of the sheets of bubble wrap that are fun to snap rather than the foam peanuts that get all over the place and are really nasty if you have a slight static charge. Does anybody have any data on the sensitivity of a crystal oscillator vs frequency of mechanical shock/vibration? Does it scale with amplitude or acceleration or ??? -- 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY From: Tom Van Baak [EMAIL PROTECTED] Subject: Re: [time-nuts] FMT on October 13 Date: Tue, 25 Sep 2007 23:45:12 -0700 Message-ID: [EMAIL PROTECTED] ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I guess it depends on signal to noise ratio. With reciprocal counters, you only need one period to measure as acurately as you need, but to have good acuracy, you need very good S/N, as there is no filtering possible. For example, the HP 5370 can measure a single period of a signal with a resolution of 20pS (excluding noise and trigger imperfections), so excluding these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal with 7 x10-5 precision (if I have not goofed the calculations) More periods improve the resolution proportionately to the quare root. Accuracy is another matter. Didier KO4BB The jitter on a single period is likely very, very high, especially if it comes over the air. That's why one usually measures over a duration of thousands or even millions of periods (effectively called the gate time). The HP 53132A makes something like 200,000 measurements per second. As a result, for a certain range of frequencies, it claims 12 digits/sec of resolution (vs. HP 5370 ~11 digits/sec). As was discussed recently, didn't they do averaging such that they updated value every second but the raw singel-shot resolution doess not give you the 12 digits/sec. There was a nice explanation in an article on how this was not improving say ADEV measurements in the end. 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I just wanted to point out that with reciprocal counters, you can get resolution much better than the 1Hz/s you would get with conventional frequency counters, even though the actual accuracy of the measurement may be way off. The original question seemed to imply that with a short transmission time, you could not guarantee a frequency accuracy of 1e-6 Hz, which you probably can't anyhow, but the limit is not the resolution of the instrument or the measurement method. I do not know how far off calibration my HP 5370s are, but the 20pS resolution is at best only usable under some circumstances that I have not isolated yet, due to jitter. When measuring a 3.5 MHz signal (@1dBm) from my HP 8657B through 1 meter of good coax cable (with counter and generator phase locked to the Thunderbolt GPSDO) in Frequency mode with a 1s gate time, the resolution is 1e-5Hz, with about 1e-3Hz p-p variation. When measuring over 1 period with 10,000 periods sample size, the resolution is only 1e-1Hz with a standard deviation of ~400 Hz (or about 0.1%). Of course, over the air, it will be much worse due to noise, let alone propagation, fading and multipath. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Van Baak Sent: Wednesday, September 26, 2007 1:45 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT on October 13 I guess it depends on signal to noise ratio. With reciprocal counters, you only need one period to measure as acurately as you need, but to have good acuracy, you need very good S/N, as there is no filtering possible. For example, the HP 5370 can measure a single period of a signal with a resolution of 20pS (excluding noise and trigger imperfections), so excluding these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal with 7 x10-5 precision (if I have not goofed the calculations) More periods improve the resolution proportionately to the quare root. Accuracy is another matter. Didier KO4BB The jitter on a single period is likely very, very high, especially if it comes over the air. That's why one usually measures over a duration of thousands or even millions of periods (effectively called the gate time). The HP 53132A makes something like 200,000 measurements per second. As a result, for a certain range of frequencies, it claims 12 digits/sec of resolution (vs. HP 5370 ~11 digits/sec). /tvb ___ 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] FMT on October 13
From: Didier Juges [EMAIL PROTECTED] Subject: Re: [time-nuts] FMT on October 13 Date: Wed, 26 Sep 2007 05:57:14 -0500 Message-ID: [EMAIL PROTECTED] Didier, I just wanted to point out that with reciprocal counters, you can get resolution much better than the 1Hz/s you would get with conventional frequency counters, even though the actual accuracy of the measurement may be way off. These days conventional counteras are reciprocal counters. It is only the old-school counters which is not reciprocal. Nothing wrong with old-school, but a conventional counter of the shelf today is probably a reciprocal jobbie. The original question seemed to imply that with a short transmission time, you could not guarantee a frequency accuracy of 1e-6 Hz, which you probably can't anyhow, but the limit is not the resolution of the instrument or the measurement method. I do not know how far off calibration my HP 5370s are, but the 20pS resolution is at best only usable under some circumstances that I have not isolated yet, due to jitter. When measuring a 3.5 MHz signal (@1dBm) from my HP 8657B through 1 meter of good coax cable (with counter and generator phase locked to the Thunderbolt GPSDO) in Frequency mode with a 1s gate time, the resolution is 1e-5Hz, with about 1e-3Hz p-p variation. When measuring over 1 period with 10,000 periods sample size, the resolution is only 1e-1Hz with a standard deviation of ~400 Hz (or about 0.1%). Of course, over the air, it will be much worse due to noise, let alone propagation, fading and multipath. When measuring over a longer period you see a different spot on the ADEV/MDEV curve. Chances are that you are more unstable there for an OCXO. Both linear and noise products will make things harder. It can be a challenge to separate the drift rate due to signal path shifts and that of the OCXO. 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Tom Van Baak said the following on 09/24/2007 08:57 PM: I would think this is especially true for non-local frequencies, such as one received over the air. I'll leave it to you FMT guys to comment on the magnitude of degradation due to transmission and reception noise. Absolutely. Probably the best real-world performance you can get with a skywave signal is on the order of 0.01 Hz. Propagation effects play havoc, but the longer the averaging period, the more short-term effects will average away. One of the reasons for the fairly long transmission periods is to both allow longer averaging, but also provide the opportunity to observe the atmospheric conditions at work. While were at it, in the case mentioned above I'm a curious about their FMT frequency standard -- if it's really accurate to parts in 10^12, as they imply, over 10 minutes. I could believe this if it were an Rb or Cs-based GPSDO. We're using an Austron 1250A OXCO that's been measured as better than 9x10e-13 for averaging times of 1 second out to 1000 seconds; over a broader range, it's better than 3x10e-12 from 0.1 seconds to 40,000 seconds. Now, an important point -- we're not trying to trim the Austron to be precisely on frequency. We're going to let it run at whatever offset it happens to be. That will help make sure that the signal doesn't have lots of zero's at the end, even though the resolution of the synthesizers driving the transmitters is limited to 0.1 Hz. We'll be comparing the Austron against a Z3801a (via my TSC-5120A analyzer) and logging the frequency difference for at least several hours prior to the test until several hours following. The TSC gives 16 digits over 1000 seconds; depending on how much jitter we see, we'll probably throw away the last two or three. Even though the Z3801A may be wandering around a bit, with successive 1000 second measurements we should have confidence in the actual frequency over 1000 second periods to at least parts in the 12s, ultimately limited by the Austron's stability. But since that's known to be in the 13s over the averaging period of interest, we think we're safe in claiming accuracy and stability of parts in the 12s. Tom, if I'm missing something in this analysis, I'm seriously open to education... By the way -- the synthesizers used to drive the transmitter amplifiers will be PTS 250 SX-51 low noise units, so hopefully the transmitted signals will have a better-than-the-average-ham-rig phase noise. The synthesizers will directly feed the driver and final amplifier stages of some vintage Kenwood TS-520 ham transceivers with no other mixing -- it'll purely be the synthesizer and a transistor buffer amp driving two vacuum tube stages to get up to about 75 watts (the rigs can run 100 watts, but we're derating -- and adding fans -- to support the long key-down times). 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Didier Juges said the following on 09/24/2007 09:40 PM: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I guess it depends on signal to noise ratio. With reciprocal counters, you only need one period to measure as acurately as you need, but to have good acuracy, you need very good S/N, as there is no filtering possible. For example, the HP 5370 can measure a single period of a signal with a resolution of 20pS (excluding noise and trigger imperfections), so excluding these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal with 7 x10-5 precision (if I have not goofed the calculations) More periods improve the resolution proportionately to the quare root. Accuracy is another matter. I did some measurements on the frequency counter capability of my 5370B some time ago, and found that the performance wasn't as good as in time interval mode. But it's still not bad -- the internal noise floor was 4x10e-11 for 1 second (using the 1 second gate time). See http://www.febo.com/time-freq/hardware/5370B/index.html 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY While were at it, in the case mentioned above I'm a curious about their FMT frequency standard -- if it's really accurate to parts in 10^12, as they imply, over 10 minutes. I could believe this if it were an Rb or Cs-based GPSDO. We're using an Austron 1250A OXCO that's been measured as better than 9x10e-13 for averaging times of 1 second out to 1000 seconds; over a broader range, it's better than 3x10e-12 from 0.1 seconds to 40,000 seconds. Ah, if they is you, then I have no more worries. Yes, using that free-running 1250A is the perfect solution; much better than using the output of a GPSDO. Now, an important point -- we're not trying to trim the Austron to be precisely on frequency. We're going to let it run at whatever offset it happens to be. That will help make sure that the signal doesn't have lots of zero's at the end, even though the resolution of the synthesizers driving the transmitters is limited to 0.1 Hz. Clever. We'll be comparing the Austron against a Z3801a (via my TSC-5120A analyzer) and logging the frequency difference for at least several hours prior to the test until several hours following. The TSC gives 16 digits over 1000 seconds; depending on how much jitter we see, we'll probably throw away the last two or three. Even though the Z3801A may be wandering around a bit, with successive 1000 second measurements we should have confidence in the actual frequency over 1000 second periods to at least parts in the 12s, ultimately limited by the Austron's stability. But since that's known to be in the 13s over the averaging period of interest, we think we're safe in claiming accuracy and stability of parts in the 12s. Yes, running the measurement for hours before and after is the right thing to do. All sounds good. Make sure not to get near any of the equipment. Free-running oscillators are sensitive to vibration or shock. You've probably heard the story of my best Sulzer oscillator making small phase or jumps which I eventually correlated to when the kids flushed the toilet down the hall. Tom, if I'm missing something in this analysis, I'm seriously open to education... Nothing missing; you nailed it. /tvb ___ 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Make sure not to get near any of the equipment. Free-running oscillators are sensitive to vibration or shock. You've probably heard the story of my best Sulzer oscillator making small phase or jumps which I eventually correlated to when the kids flushed the toilet down the hall. Did mounting it on a block of foam help? -- 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.
[time-nuts] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY The Midwest VHF/UHF Society (located in Southwest Ohio) is pleased to announce that the first annual MVUS Frequency Measuring Test will be held on Saturday, October 13, 2007. There will be two transmission periods: the first at 14:30 EDT (1830 UTC), and the second at 21:30 EDT (0130 UTC Sunday). Transmissions will be on the 80M, 40M, and 30M amateur bands from Dayton, Ohio under the callsign W8KSE. Frequencies will be approximately: 3555 kHz, 7055 kHz, and 10115 kHz, but be prepared to tune as we will adjust to minimize QRM. The transmitters will be running about 75 watts output into wire antennas for each band. All the transmitters will be driven from a common frequency standard. We will transmit on all three bands simultaneously. Plans are to transmit two 10 minute test periods, and a third if the transmitters aren't melting by that point. The frequency will be changed by a small amount (less than 200 Hz) between transmission periods. So, a complete submission will include two or three separate measurements for each band. Our goal is to transmit a signal known in frequency to parts in 10e-12 (i.e., less than 0.0001 Hz error at 10 MHz) and stable to a similar level during the course of the transmission. Frequencies will be measured at the transmitter site with a system capable of microHertz resolution referenced to a GPS disciplined oscillator, and will also be monitored by another station in groundwave range that can measure the frequencies with similar accuracy. The MVUS Frequency Measuring Test is intended to supplement, not replace, the ARRL FMT. Further information, including approximate transmission frequencies, will be posted at http://www.febo.com/time-freq/FMT. You can also send email with questions or comments (or, after the test, your results!) to [EMAIL PROTECTED]. For discussion about off-air frequency measurement, we suggest you check out the FMT-nuts mailing list, sponsored by Connie Marshall, K5CM. For details, go to http://tech.groups.yahoo.com/group/FMT-nuts/. ___ 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] FMT on October 13
Plans are to transmit two 10 minute test periods, and a third if the transmitters aren't melting by that point. Our goal is to transmit a signal known in frequency to parts in 10e-12 (i.e., less than 0.0001 Hz error at 10 MHz) and stable to a similar level during the course of the transmission. Frequencies will be measured at the transmitter site with a system capable of microHertz resolution referenced to a GPS disciplined oscillator, and will also be monitored by another station in groundwave range that can measure the frequencies with similar accuracy. Suppose I have a pile of good lab gear, and it gets N seconds of signal. How accurately can it measure the frequency? -- 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] FMT on October 13
Plans are to transmit two 10 minute test periods, and a third if the transmitters aren't melting by that point. Our goal is to transmit a signal known in frequency to parts in 10e-12 (i.e., less than 0.0001 Hz error at 10 MHz) and stable to a similar level during the course of the transmission. Frequencies will be measured at the transmitter site with a system capable of microHertz resolution referenced to a GPS disciplined oscillator, and will also be monitored by another station in groundwave range that can measure the frequencies with similar accuracy. Suppose I have a pile of good lab gear, and it gets N seconds of signal. How accurately can it measure the frequency? Hi Hal, If you have a low noise CW signal, a cheap, legacy 1 ns resolution counter will give you 9 digits of resolution per second. So to measure to parts in 10^12 requires gate times on the order of a thousand seconds. A fancier, modern counter like a HP 53132A is almost ten times better than that so 100 s gate times are all you need for 12 digits. Further, if it's an oddball frequency (i.e., not a nice multiple or fraction of 10 MHz) even 10 second gate times are sufficient with this counter (it does clever CW oversampling inside). For extreme counters like HP 5370 or SR 620 with resolution well under 50 ps you can measure any frequency to 12 digits in a matter of tens of seconds. The main problems at this level are often that neither your frequency reference nor the frequency you are measuring are stable to parts in 10^12th. So the measurements you get will contain the sum of noise in both sources and the counter itself. And this noise is often well above parts in 10^12th. It takes time, statistics, or other tests to determine the noise contribution of each. I would think this is especially true for non-local frequencies, such as one received over the air. I'll leave it to you FMT guys to comment on the magnitude of degradation due to transmission and reception noise. While were at it, in the case mentioned above I'm a curious about their FMT frequency standard -- if it's really accurate to parts in 10^12, as they imply, over 10 minutes. I could believe this if it were an Rb or Cs-based GPSDO. Usually the accuracy of GPS disciplined oscillators are spec'd for averaging times over a day. And at one day, parts in 10^12 is very easy (many are down in the low 13's or 14's). But over a short span like 10 minutes most quartz-based GPSDO wander in frequency by many parts in 10^11. See, for example, these two nice quartz GPSDO over 10 minutes and note the scale is 1e-11 per *division*; which is almost 1e-10 full-scale. http://www.leapsecond.com/pages/fury/#6 /tvb ___ 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] FMT on October 13
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I guess it depends on signal to noise ratio. With reciprocal counters, you only need one period to measure as acurately as you need, but to have good acuracy, you need very good S/N, as there is no filtering possible. For example, the HP 5370 can measure a single period of a signal with a resolution of 20pS (excluding noise and trigger imperfections), so excluding these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal with 7 x10-5 precision (if I have not goofed the calculations) More periods improve the resolution proportionately to the quare root. Accuracy is another matter. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hal Murray Sent: Monday, September 24, 2007 5:26 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT on October 13 Plans are to transmit two 10 minute test periods, and a third if the transmitters aren't melting by that point. Our goal is to transmit a signal known in frequency to parts in 10e-12 (i.e., less than 0.0001 Hz error at 10 MHz) and stable to a similar level during the course of the transmission. Frequencies will be measured at the transmitter site with a system capable of microHertz resolution referenced to a GPS disciplined oscillator, and will also be monitored by another station in groundwave range that can measure the frequencies with similar accuracy. Suppose I have a pile of good lab gear, and it gets N seconds of signal. How accurately can it measure the frequency? -- 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. ___ 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] FMT on October 13
Didier Juges wrote: I guess it depends on signal to noise ratio. With reciprocal counters, you only need one period to measure as acurately as you need, but to have good acuracy, you need very good S/N, as there is no filtering possible. For example, the HP 5370 can measure a single period of a signal with a resolution of 20pS (excluding noise and trigger imperfections), so excluding these errors, the HP 5370 could measure a single period of a ~3.5 MHz signal with 7 x10-5 precision (if I have not goofed the calculations) More periods improve the resolution proportionately to the quare root. Accuracy is another matter. Didier KO4BB Didier With band limited gaussian noise and an SNR of 40dB the rms error in measuring the period of a single cycle is about 0.3% Bruce ___ 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] FMT
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I will be continuing the two frequency FMT on 80 meters tonight. The current span is about 100 Hz. When most of the Doppler is removed from the equation, calibration becomes the overriding factor. Check out the details on the Website and give it a try. http://pages.suddenlink.net/k5cm/ 73 Connie K5CM ___ 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] FMT today/tonight
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I will be doing a 17,20,40, and 80 meter run. Marvin will be doing the West Coast run on 40 meters. Check the website for time and details. http://pages.suddenlink.net/k5cm/ 73 Connie K5CM ___ 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] FMT Wednesday night
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY See details at: http://pages.suddenlink.net/k5cm/ 73 Connie K5CM ___ 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] FMT Wednesday night
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] See the website for details: http://pages.suddenlink.net/k5cm/ 73 Connie K5CM ___ 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] FMT
Tonight at 02:30 utc. I expect QRM problems from N6WK, so I may have to move several KHz from my normal frequency. details here: http://pages.suddenlink.net/k5cm/ Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hi Connie, My life has been a little complicated lately, but it will settle eventually :-) I was surprised to be so close just by ear. 20m was hard because of QSB, but 40 and 80 were good, with strong and stable signals. I have Spectrum Lab installed on this new to me laptop, so next week should be better. I will use the HP 8657B instead of the HP 3586 (the lack of attenuator on the 3586 TG output makes it hard to adjust the level of the injection signal). Resolution drops to 1 Hz instead of 0.1 Hz, but with Spectrum Lab, that should be fine. Thanks for running this exercise. That is most interesting. I wish ARRL had such a good setup... 73, Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Connie Marshall Sent: Saturday, May 26, 2007 10:43 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT Hi Didier, Good to hear from you. Sounds like you did fine considering how bad condx were that night. I will send out an email on the time and frequency. I think it will be Thursday night this week, but not sure yet. Thanks for participating and have a good weekend 73 Connie K5CM -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Didier Juges Sent: Saturday, May 26, 2007 8:11 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT Well, I was too late sending my results, but I did manage to listen to the signals this past Wednesday. I did not have time to prepare anything but listening by ear on the FT-1000 and using the HP-3586A as a beat generator (free running off it's internal Ovenair precision OCXO), I managed to get within 0.4 Hz on 40 m and 0.2 Hz on 80m (good signals). I was off by 1.5 Hz on 20m, where the signal was very weak with QSB, and I did not hear anything on 17m. Thanks Connie, I will try to be better prepared next week (hooked to GPS and using Spectrum Lab). Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.467 / Virus Database: 269.8.0/818 - Release Date: 5/25/2007 12:32 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Well, I was too late sending my results, but I did manage to listen to the signals this past Wednesday. I did not have time to prepare anything but listening by ear on the FT-1000 and using the HP-3586A as a beat generator (free running off it's internal Ovenair precision OCXO), I managed to get within 0.4 Hz on 40 m and 0.2 Hz on 80m (good signals). I was off by 1.5 Hz on 20m, where the signal was very weak with QSB, and I did not hear anything on 17m. Thanks Connie, I will try to be better prepared next week (hooked to GPS and using Spectrum Lab). Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hi Didier, Good to hear from you. Sounds like you did fine considering how bad condx were that night. I will send out an email on the time and frequency. I think it will be Thursday night this week, but not sure yet. Thanks for participating and have a good weekend 73 Connie K5CM -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Didier Juges Sent: Saturday, May 26, 2007 8:11 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT Well, I was too late sending my results, but I did manage to listen to the signals this past Wednesday. I did not have time to prepare anything but listening by ear on the FT-1000 and using the HP-3586A as a beat generator (free running off it's internal Ovenair precision OCXO), I managed to get within 0.4 Hz on 40 m and 0.2 Hz on 80m (good signals). I was off by 1.5 Hz on 20m, where the signal was very weak with QSB, and I did not hear anything on 17m. Thanks Connie, I will try to be better prepared next week (hooked to GPS and using Spectrum Lab). Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
Next FMT details at: http://pages.suddenlink.net/k5cm/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
I will do a early 17 meter run. Check the website for details: http://pages.suddenlink.net/k5cm/ 73 Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT -Saturday and Sunday
For details see: http://pages.suddenlink.net/k5cm/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
For details of the next run see: http://pages.suddenlink.net/k5cm/ Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
The next FMT will be Wednesday night April 18. It will be one hour later than normal this week. 11:30 PM EDT 10:30 PM CDT 9:30 PM MDT 8:30 PM PDT 3:30 UTC (Thursday UTC) 80 near 355 Hz 40 near 7055000 Hz 160 near 1887000 Hz Send your results and comments with in 22 hours to [EMAIL PROTECTED] Put Sudden FMT, your Call, your state, and frequency in Hz, in the subject line. i.e. - Sudden FMT, K5CM, OK, 3550300.1 Hz, 7055034.73 Hz, 1887128.55 Hz http://pages.suddenlink.net/k5cm Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT April 11 results
Results are at: http://pages.suddenlink.net/k5cm If you have already viewed the results, you might want to check again. I just added more comments a few minutes ago. Connie K5CM ___ time-nuts mailing list [EMAIL PROTECTED] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
Results of Wednesdays FMT are now at http://pages.suddenlink.net/k5cm If you missed this one, there will be another FMT next Wednesday. 73 Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT Practice
As most of us know its one thing to practice on WWV or CHU and totally another to find and measure the frequency of an unknown signal in a short time period. So with that in mind I though it would be fun to do some practice FMT's. I have been running tests with Joe KM1P in Boston, and we think 80 meters would be the best band for general coverage from the central USA. Joe, thanks for all your help! The first frequency measuring test will be Thursday March 29 at 02:30 UTC (Wednesday nite local time). I will use a little different format than W1AW. There will be a single two minute key down period. There will be at least a 10 second silent time before and after the two minute key down.The frequency will be near 355 Hz. Send your results to [EMAIL PROTECTED] I will post the TX Frequency and best readings on my website at http://pages.suddenlink.net/k5cm My accuracy will not be as good as Mike WA6ZTY, but should be at least as good, and hopefully better, than W1AW. Current equipment Standard: HP Z3801 Transceiver: FT1000D Software: Spectrum Lab Antenna: 80 meter cage dipole for Tx and Beverage for Rx Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT Results Published !
Mike Fahmie wrote: 2006 FMT results have appeared at: http://www.arrl.org/w1aw/fmt/2006/2006-fmt-results.html It is curious that none of us managed to be within 1 Hz on 3 bands. I missed out by 1.4 Hz on 40M ... but then there were a lot of us who measured on the low side on 40 relative to the umpire. -Joe KM1P Boston MA ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT Results Published !
It was also interesting to note that there were four stations within 1Hz, on three of the four bands, and all four were over 1Hz high on W1AW 40 meters. The station that copied both 40 meters signals to less than 1Hz was off by more than 1Hz on the other two bands. Here are my results if any one wants to fill in call signs on the spread sheet. In the old FMT days call signs were published with the results. 160 -0.27 80 -0.45 40 -1.13 WA6ZTY 40 -0.07 Connie K5CM Oklahoma -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Mike Fahmie Sent: Wednesday, March 07, 2007 11:59 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT Results Published ! At 07:05 AM 3/7/2007, you wrote: Mike Fahmie wrote: 2006 FMT results have appeared at: http://www.arrl.org/w1aw/fmt/2006/2006-fmt-results.html It is curious that none of us managed to be within 1 Hz on 3 bands. I missed out by 1.4 Hz on 40M ... but then there were a lot of us who measured on the low side on 40 relative to the umpire. -Joe KM1P Boston MA There are a number of things that point toward W1AW being about a hertz high. 1.) Though W1AW received nearly 3 times as many 40M reports as WA6ZTY, each had nearly the same number of reports in the 1 Hz group, but W1AW had 4 times as many in the 1 to 5 Hz group. 2.) If you look at entries who were in the 1 Hz group on other measurements, they were all about 1 Hz low on W1AW's 40 M signal. 3.) Only one person who copied WA6ZTY 1 Hz copied W1AW 1 Hz. -Mike- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT Results Published !
Connie Marshall wrote: In the old FMT days call signs were published with the results. Here are mine : 160 0.1 80 -0.5 40 -1.4 WA6TZY 40 No copy -Joe KM1P Boston MA USA ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT Results Published !
One more set: (from PA) 1600 80 -0.1 40 -1.4 WA6ZTY -1.83 ( I made a stupid 2 Hz math error - my actual measurement was -0.17) I agree, it looks like the W1AW 40 M measurement was off. BR On 3/7/07, Joe Fitzgerald [EMAIL PROTECTED] wrote: Connie Marshall wrote: In the old FMT days call signs were published with the results. Here are mine : 160 0.1 80 -0.5 40 -1.4 WA6TZY 40 No copy -Joe KM1P Boston MA USA ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT Results Published !
2006 FMT results have appeared at: http://www.arrl.org/w1aw/fmt/2006/2006-fmt-results.html -Mike- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
I received my letter yesterday and the ARRL stayed with the same numbers I posted last month. Based on mine, and other reports I beleve their 40 meter reading is probably low by around 1Hz. I read the W1AW 40 meter frequency 1.13 Hz higher. My copy on W1AW was strong and stable at the time. I read the WA6ZTY 40 meter frequence .07Hz higher. W1AW Posted frequency 160 meters: 1854317.5 Hz 80 meters: 3587117.5 Hz 40 meters: 7038804.9 Hz WA6ZTY Posted frequency 40 meters: 7028351.47 Hz Connie k5cm ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT 2006 results
John and others, I didn't play in this game so I haven't been paying close attention to the contest or results. In my skimming of the messages I think I am hearing that several knowledgeable people came out with results close to each other but offset from the winning results. If I am correct in my assessment, seems like the ARRL should be made aware that the process or the specification of the contest signal may be lacking in some details. What do you think was the issue? Was it a modulated carrier on SSB with some residual rather than pure CW? If there is some consensus of close mis-measured results in this group, seems like the ARRL needs to be informed about it so exactly what the signal is is described or the contest is modified with a better pure CW carrier in the future. Am I right, or am I completely missing the point in some way? -Rex On Thu, 4 Jan 2007 00:54:34 -0600, Connie Marshall [EMAIL PROTECTED] wrote: Looks good John Our readdings are within .03Hz on 160, .1Hz on 80, and .06Hz on 40 of each other. Connie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John Ackermann N8UR Sent: Wednesday, January 03, 2007 9:33 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] FMT 2006 results I've put my FMT results at http://www.febo.com/time-freq/fmt/fmt2006/ based on the preliminary numbers from ARRL that Connie posted here. As I noted earlier, I screwed up the math and ended up being off on all three bands by 75 to 110 Hz -- double the delta between W1AW and my marker, because I did USB math when the receivers were set to LSB. After correcting that error, I was -0.295 Hz on 160, -0.343 Hz on 40, and -1.066 Hz on 40. That's a bit more like it, though the error on 40 is interesting, and I see that a few other folks saw that problem, too. We'll have to wait for the final results from W1AW to see if their 40M frequency had a typo. I think a couple of other folks noted, as did I, that on 40M there appeared to be two signals close to each other (I measured about 0.5 Hz). An FFT with enough resolution to separate them lost any ability to look for CW in the waterfall, so I had to guess which was the correct signal. I chose the sharper one, which was the higher frequency of the two; had I picked the one that was more smeared out, I would have been more like -0.5 Hz off. I've learned my lesson -- from now on, all measurements will be taken in USB mode! John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT 2006 results
if it turns out that there really is an anomaly on 40M, we'll let ARRL know; last year they were off by about 0.4Hz on 160M so something like this isn't a first. One problem is that they really don't aim the test at the time-nuts crowd, and frankly their measurement system isn't at the level some of us would like to see. And the change of transmitter hardware this year didn't help. I don't want to go into details on the list, but there is some activity going on to try to improve the situation next year. John - Rex wrote: John and others, I didn't play in this game so I haven't been paying close attention to the contest or results. In my skimming of the messages I think I am hearing that several knowledgeable people came out with results close to each other but offset from the winning results. If I am correct in my assessment, seems like the ARRL should be made aware that the process or the specification of the contest signal may be lacking in some details. What do you think was the issue? Was it a modulated carrier on SSB with some residual rather than pure CW? If there is some consensus of close mis-measured results in this group, seems like the ARRL needs to be informed about it so exactly what the signal is is described or the contest is modified with a better pure CW carrier in the future. Am I right, or am I completely missing the point in some way? -Rex On Thu, 4 Jan 2007 00:54:34 -0600, Connie Marshall [EMAIL PROTECTED] wrote: Looks good John Our readdings are within .03Hz on 160, .1Hz on 80, and .06Hz on 40 of each other. Connie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John Ackermann N8UR Sent: Wednesday, January 03, 2007 9:33 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] FMT 2006 results I've put my FMT results at http://www.febo.com/time-freq/fmt/fmt2006/ based on the preliminary numbers from ARRL that Connie posted here. As I noted earlier, I screwed up the math and ended up being off on all three bands by 75 to 110 Hz -- double the delta between W1AW and my marker, because I did USB math when the receivers were set to LSB. After correcting that error, I was -0.295 Hz on 160, -0.343 Hz on 40, and -1.066 Hz on 40. That's a bit more like it, though the error on 40 is interesting, and I see that a few other folks saw that problem, too. We'll have to wait for the final results from W1AW to see if their 40M frequency had a typo. I think a couple of other folks noted, as did I, that on 40M there appeared to be two signals close to each other (I measured about 0.5 Hz). An FFT with enough resolution to separate them lost any ability to look for CW in the waterfall, so I had to guess which was the correct signal. I chose the sharper one, which was the higher frequency of the two; had I picked the one that was more smeared out, I would have been more like -0.5 Hz off. I've learned my lesson -- from now on, all measurements will be taken in USB mode! John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT 2006 results
I've put my FMT results at http://www.febo.com/time-freq/fmt/fmt2006/ based on the preliminary numbers from ARRL that Connie posted here. As I noted earlier, I screwed up the math and ended up being off on all three bands by 75 to 110 Hz -- double the delta between W1AW and my marker, because I did USB math when the receivers were set to LSB. After correcting that error, I was -0.295 Hz on 160, -0.343 Hz on 40, and -1.066 Hz on 40. That's a bit more like it, though the error on 40 is interesting, and I see that a few other folks saw that problem, too. We'll have to wait for the final results from W1AW to see if their 40M frequency had a typo. I think a couple of other folks noted, as did I, that on 40M there appeared to be two signals close to each other (I measured about 0.5 Hz). An FFT with enough resolution to separate them lost any ability to look for CW in the waterfall, so I had to guess which was the correct signal. I chose the sharper one, which was the higher frequency of the two; had I picked the one that was more smeared out, I would have been more like -0.5 Hz off. I've learned my lesson -- from now on, all measurements will be taken in USB mode! John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT 2006 results
Looks good John Our readdings are within .03Hz on 160, .1Hz on 80, and .06Hz on 40 of each other. Connie -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of John Ackermann N8UR Sent: Wednesday, January 03, 2007 9:33 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] FMT 2006 results I've put my FMT results at http://www.febo.com/time-freq/fmt/fmt2006/ based on the preliminary numbers from ARRL that Connie posted here. As I noted earlier, I screwed up the math and ended up being off on all three bands by 75 to 110 Hz -- double the delta between W1AW and my marker, because I did USB math when the receivers were set to LSB. After correcting that error, I was -0.295 Hz on 160, -0.343 Hz on 40, and -1.066 Hz on 40. That's a bit more like it, though the error on 40 is interesting, and I see that a few other folks saw that problem, too. We'll have to wait for the final results from W1AW to see if their 40M frequency had a typo. I think a couple of other folks noted, as did I, that on 40M there appeared to be two signals close to each other (I measured about 0.5 Hz). An FFT with enough resolution to separate them lost any ability to look for CW in the waterfall, so I had to guess which was the correct signal. I chose the sharper one, which was the higher frequency of the two; had I picked the one that was more smeared out, I would have been more like -0.5 Hz off. I've learned my lesson -- from now on, all measurements will be taken in USB mode! John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
My numbers were: W1AW (40 m band): 7038806.3 Hz (1.4 Hz higher than the official reading) WA6ZTY: 7028351.5 Hz (0.03 Hz higher than the official reading) I only submitted readings to the nearest 100 mHz (that is, 0.1 Hz), as I didn't think my measurements supported more digits of precision than that. I could not copy W1AW by ear, although I did pick out the call sign once during the test. I could not copy the announcements of when they were measuring the 160 m, or the 80 m, or the 40 m signal. I only saw a faint waterfall trace, and only on 40 m. -- James Maynard, K7KK Salem, Oregon, USA ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Mike Suhar said the following on 12/29/2006 02:32 PM: I used an HP 3586C Frequency Selective Voltmeter with the tracking generator looped back to the RF input via a step attenuator. The audio output went to the PC. An ICOM IC-745 was tuned to the 160M signal to hear the test announcements throughout the test period. The antenna on the HP was a SWL slopper antenna that favors the lower frequencies. The ICOM was on a 40-meter dipole. I too use the 3586C but there is one thing to be aware of: while the main frequency synthesis system can be locked to an external reference, the BFO signal comes from an independent oscillator that is not disciplined. The last IF is at 15.625 kHz and the BFO frequency (generated on board A22) is (for the C version) is either 17.475 kHz (USB) or 13.775 kHz (LSB). The BFO is derived from a crystal -- 1.7475 MHz for USB and 1.3775 MHz for LSB; the crystal frequency is divided by 100. Interestingly, it appears that the BFO signal is injected into the product detector as a square wave; unless I missed it, there's no filter following the divider. After a bit of warm-up, the BFO is very stable (dividing by 100 certainly helps reduce any drift) but the nominal 1850 Hz tone generated by a signal on the tuned frequency is likely to be off by a fraction of a Hertz. One of my plans is to build a BFO synthesizer to replace the crystals and thereby eliminate any frequency offset. Having done that I should be able to directly determine frequency by measuring the output tone. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
I didn't enter the FMT due to the lack of an HF antenna, but my original plan was to downconvert the signal with a GPS-locked LO, then run it through a logamp and a very narrow CW filter and straight into my 5370B without any demodulation at all. As long as there were no interferers within the CW filter's bandwidth -- which it sounds like there may have been -- that should have worked about as well as any other technique. Does the 3586C have an AGC-controlled IF output? A BFO synthesizer would be a good idea, but it might not be necessary if you can filter and measure the IF directly. -- john, KE5FX One of my plans is to build a BFO synthesizer to replace the crystals and thereby eliminate any frequency offset. Having done that I should be able to directly determine frequency by measuring the output tone. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
John Miles said the following on 12/29/2006 03:24 PM: Does the 3586C have an AGC-controlled IF output? A BFO synthesizer would be a good idea, but it might not be necessary if you can filter and measure the IF directly. It has an IF output as well as a built in counter with 0.1 Hz resolution. However, there is no AGC as such. You can put it into a 100dB dynamic range mode, which reduces sensitivity, or in an autoranging mode where the gain is stepped in 10dB increments. Or you can turn the ranging off and manually set the gain. The autoranging results in transients that are annoying in a waterfall, so I usually set the range manually and live with a bit of distortion if it overloads from time to time. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
Here are the W1AW FMT Numbers I just received from Joe, NJ1Q (W1AW Station Manager) 160m - 1854317.5 Hz 80m - 3587117.5 40m - 7038804.9 Hz My copy of W1AW: 160M 1854317.77 Hz 80M 3587117.95 Hz 40M 7038806.03 Hz I missed the 40m W1AW frequency by 1 Hz for some reason Hmm.. I will go back and replay my audio file and see if I made a math mistake some where. My copy of WA6ZTY 40M - 7028351.545 Hz Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
Here is the WA6ZTY tx frequency: 40 Meters - 7028351.47 Hz My reading: 7028351.54 Hz I'm only off by .07 Hz here, so I feel my system was calibrated OK. Not yet sure why my reading on W1AW 40m was so far off (1 Hz). Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Bill Tracey said the following on 12/28/2006 06:41 PM: I too got a 1hz high error on W1AW on 40. As I recall, the data had a double peak in it - think I picked the stronger peak which apparently was the wrong one. Apparently the propagation on 40 was interesting when the test was run. I have to admit that I screwed up royally this year and had a math error that threw all my results off by 70 to 100 Hz (stupid error -- getting my sideband math backwards). I'll get my results up on the web site soon, both as submitted and what they would have been with the correct math. But I wanted to mention that I also saw a double hump on 40M, with about 0.5 Hz separation. I wonder if it was an artifact of the transmitter, or one of propagation. As I understand it, the League this year used regular ham transceivers instead of the old Harris rigs. On 160 and 80 they had Ten-Tecs, and on 40 I think an Icom. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hi Bill, Several others have now said they were off by 1 Hz on 40m. Possibly Joe ( W1AW Station manager) typed the frequency wrong to my email, or W1AW measured the freq incorrectly that night or as John mentioned there was a artifact from the transmitter, or the Doppler was indeed that bad. I still need to go back and look and my audio file with Spectran again. As I mentioned in an earlier email I was only off by .07 Hz on the WA6ZTY run so I tend to think my system was working properly on 40m hmm. Connie K5CM -Original Message- From: Bill Tracey [mailto:[EMAIL PROTECTED] Sent: Thursday, December 28, 2006 5:41 PM To: [EMAIL PROTECTED]; Discussion of precise time and frequency measurement; Time-Nuts Subject: Re: [time-nuts] FMT Very interesting - the measurements I submitted were: 160: 1854317.63 80: 3857117.47 40: 7038806.11 40 (west coast): 7028351.61 I too got a 1hz high error on W1AW on 40. As I recall, the data had a double peak in it - think I picked the stronger peak which apparently was the wrong one. Apparently the propagation on 40 was interesting when the test was run. Cheers, Bill (kd5tfd) At 02:25 PM 12/28/2006, Connie Marshall wrote: Here are the W1AW FMT Numbers I just received from Joe, NJ1Q (W1AW Station Manager) 160m - 1854317.5 Hz 80m - 3587117.5 40m - 7038804.9 Hz My copy of W1AW: 160M 1854317.77 Hz 80M 3587117.95 Hz 40M 7038806.03 Hz I missed the 40m W1AW frequency by 1 Hz for some reason Hmm.. I will go back and replay my audio file and see if I made a math mistake some where. My copy of WA6ZTY 40M - 7028351.545 Hz Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Interesting! My numbers: 160: 1854317.9 80: 3587117.6 40: 7308806.0 Henry KB7NIE On 12/28/06, Connie Marshall [EMAIL PROTECTED] wrote: Hi Bill, Several others have now said they were off by 1 Hz on 40m. Possibly Joe ( W1AW Station manager) typed the frequency wrong to my email, or W1AW measured the freq incorrectly that night or as John mentioned there was a artifact from the transmitter, or the Doppler was indeed that bad. I still need to go back and look and my audio file with Spectran again. As I mentioned in an earlier email I was only off by .07 Hz on the WA6ZTY run so I tend to think my system was working properly on 40m hmm. Connie K5CM -Original Message- From: Bill Tracey [mailto:[EMAIL PROTECTED] Sent: Thursday, December 28, 2006 5:41 PM To: [EMAIL PROTECTED]; Discussion of precise time and frequency measurement; Time-Nuts Subject: Re: [time-nuts] FMT Very interesting - the measurements I submitted were: 160: 1854317.63 80: 3857117.47 40: 7038806.11 40 (west coast): 7028351.61 I too got a 1hz high error on W1AW on 40. As I recall, the data had a double peak in it - think I picked the stronger peak which apparently was the wrong one. Apparently the propagation on 40 was interesting when the test was run. Cheers, Bill (kd5tfd) At 02:25 PM 12/28/2006, Connie Marshall wrote: Here are the W1AW FMT Numbers I just received from Joe, NJ1Q (W1AW Station Manager) 160m - 1854317.5 Hz 80m - 3587117.5 40m - 7038804.9 Hz My copy of W1AW: 160M 1854317.77 Hz 80M 3587117.95 Hz 40M 7038806.03 Hz I missed the 40m W1AW frequency by 1 Hz for some reason Hmm.. I will go back and replay my audio file and see if I made a math mistake some where. My copy of WA6ZTY 40M - 7028351.545 Hz Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hey Henry Looks like your W1AW 40m numbers are in line with the others. I just checked my audio wave file with spectran, and the 40 meter signal was strong and stable. Joe (W1AW station manager)said he would post the results to the W1AW/FMT website soon, so we will wait and see if it is the same numbers as he gave me today in his email. Connie K5CM -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Henry Knoepfle Sent: Thursday, December 28, 2006 9:47 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT Interesting! My numbers: 160: 1854317.9 80: 3587117.6 40: 7308806.0 Henry KB7NIE On 12/28/06, Connie Marshall [EMAIL PROTECTED] wrote: Hi Bill, Several others have now said they were off by 1 Hz on 40m. Possibly Joe ( W1AW Station manager) typed the frequency wrong to my email, or W1AW measured the freq incorrectly that night or as John mentioned there was a artifact from the transmitter, or the Doppler was indeed that bad. I still need to go back and look and my audio file with Spectran again. As I mentioned in an earlier email I was only off by .07 Hz on the WA6ZTY run so I tend to think my system was working properly on 40m hmm. Connie K5CM -Original Message- From: Bill Tracey [mailto:[EMAIL PROTECTED] Sent: Thursday, December 28, 2006 5:41 PM To: [EMAIL PROTECTED]; Discussion of precise time and frequency measurement; Time-Nuts Subject: Re: [time-nuts] FMT Very interesting - the measurements I submitted were: 160: 1854317.63 80: 3857117.47 40: 7038806.11 40 (west coast): 7028351.61 I too got a 1hz high error on W1AW on 40. As I recall, the data had a double peak in it - think I picked the stronger peak which apparently was the wrong one. Apparently the propagation on 40 was interesting when the test was run. Cheers, Bill (kd5tfd) At 02:25 PM 12/28/2006, Connie Marshall wrote: Here are the W1AW FMT Numbers I just received from Joe, NJ1Q (W1AW Station Manager) 160m - 1854317.5 Hz 80m - 3587117.5 40m - 7038804.9 Hz My copy of W1AW: 160M 1854317.77 Hz 80M 3587117.95 Hz 40M 7038806.03 Hz I missed the 40m W1AW frequency by 1 Hz for some reason Hmm.. I will go back and replay my audio file and see if I made a math mistake some where. My copy of WA6ZTY 40M - 7028351.545 Hz Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT -- 40M strangeness?
John Ackermann N8UR wrote: Without giving away any actual numbers, did anyone else notice either a fuzzy signal, or some interference within about 1 Hz of W1AW on 40M? I recorded the entire test run and have been unable to prove to myself exactly where W1AW is; almost any sample of data I select shows two signals within about 1 Hz -- depending on just what segment of the data I analyze, I can sometimes get one peak that is sharper and another that is smeared out over about 0.5Hz, but I'm not confident about which one is the real thing. An FFT with enough bins to separate the two signals loses the CW keying, so I can't use that to see which one is real. Again, nobody post actual frequencies, but if you've looked at the 40M signal very closely, I'd appreciate finding out whether this is local to me, or something others saw. Thanks, John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts . For me, the W1AW signal was quite faint. It was visible on Specturm Lab's waterfall display as a rather broad, fuzzy trace, but I could not copy it by ear. (I did, once, hear the call sign, W1AW.) So my measurement of its frequency was by averaging the Sprectrum Lab text output (File | Text file export... | Export of calculated data) after I had imported into a Microsoft Excel file. I computed a mean of the data in one of the spreadsheet columns to get the frequency that I used in my FMT submission. I also computed the standard deviation of that column, and saw that it was spread over several hertz. You were closer to W1AW, and had a stronger signal to work with than I. But I surmise that were seeing the same phenonemon: ionospheric doppler -- and especially the effect of multipath on the doppler-shifted signal. Suppose that, at the time of the FMT, the ionosphere was rising. (It usually does at and after sunset.) I assume that you were beyond the ground-wave coverage zone of W1AW, but were getting it on sky-wave. Let's denote the frequencies of the W1AW signal as transmitted (or received on ground wave), and after one-hop, two-hop, etc. skywave reflections as follows: f0 = transmitted frequency = frequency as received on groundwave f1 = frequency as received after one reflection from the ionoshphere f2 = frequency after two reflections f3 = frequency after three reflections etc, If the ionosphere is moving, f1 will differ from f0 by some amount that depends at the rate at which the ionosphere is moving. For two-hop reception, f2 will differ from f1 by a similar amount -- but not exactly the same, because of differences in the angles of incidence to the reflecting surface. I surmise that the strongest signal you received was proably W1AW as received at frequency f1 (after one hop) and the second, fainter trace was W1AW as received at frequency f2 (after two hops). You are probably beyond the zone of ground-wave reception, so you did not receive W1AW at its actual transmitted frequency, f0. Which leads to an interesting possibility. If you assume that the difference, f1-f0, is almost the same as the difference, f2-f1, you may be able to use this information to infer the true transmitted frequency, f0. I, on the other hand, had such faint and blurred reception that I was unable to discrimate between f1, f2, f3, etc., and so could not try to compute f0. -- James Maynard, K7KK Salem, Oregon, USA ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT -- 40M strangeness?
Really interesting analysis, James. I'll need to do some checking to determine my distance from W1AW, and where that puts me in the skip zone. John James Maynard said the following on 11/19/2006 02:08 PM: John Ackermann N8UR wrote: Without giving away any actual numbers, did anyone else notice either a fuzzy signal, or some interference within about 1 Hz of W1AW on 40M? I recorded the entire test run and have been unable to prove to myself exactly where W1AW is; almost any sample of data I select shows two signals within about 1 Hz -- depending on just what segment of the data I analyze, I can sometimes get one peak that is sharper and another that is smeared out over about 0.5Hz, but I'm not confident about which one is the real thing. An FFT with enough bins to separate the two signals loses the CW keying, so I can't use that to see which one is real. Again, nobody post actual frequencies, but if you've looked at the 40M signal very closely, I'd appreciate finding out whether this is local to me, or something others saw. Thanks, John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts . For me, the W1AW signal was quite faint. It was visible on Specturm Lab's waterfall display as a rather broad, fuzzy trace, but I could not copy it by ear. (I did, once, hear the call sign, W1AW.) So my measurement of its frequency was by averaging the Sprectrum Lab text output (File | Text file export... | Export of calculated data) after I had imported into a Microsoft Excel file. I computed a mean of the data in one of the spreadsheet columns to get the frequency that I used in my FMT submission. I also computed the standard deviation of that column, and saw that it was spread over several hertz. You were closer to W1AW, and had a stronger signal to work with than I. But I surmise that were seeing the same phenonemon: ionospheric doppler -- and especially the effect of multipath on the doppler-shifted signal. Suppose that, at the time of the FMT, the ionosphere was rising. (It usually does at and after sunset.) I assume that you were beyond the ground-wave coverage zone of W1AW, but were getting it on sky-wave. Let's denote the frequencies of the W1AW signal as transmitted (or received on ground wave), and after one-hop, two-hop, etc. skywave reflections as follows: f0 = transmitted frequency = frequency as received on groundwave f1 = frequency as received after one reflection from the ionoshphere f2 = frequency after two reflections f3 = frequency after three reflections etc, If the ionosphere is moving, f1 will differ from f0 by some amount that depends at the rate at which the ionosphere is moving. For two-hop reception, f2 will differ from f1 by a similar amount -- but not exactly the same, because of differences in the angles of incidence to the reflecting surface. I surmise that the strongest signal you received was proably W1AW as received at frequency f1 (after one hop) and the second, fainter trace was W1AW as received at frequency f2 (after two hops). You are probably beyond the zone of ground-wave reception, so you did not receive W1AW at its actual transmitted frequency, f0. Which leads to an interesting possibility. If you assume that the difference, f1-f0, is almost the same as the difference, f2-f1, you may be able to use this information to infer the true transmitted frequency, f0. I, on the other hand, had such faint and blurred reception that I was unable to discrimate between f1, f2, f3, etc., and so could not try to compute f0. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT -- 40M strangeness?
Without giving away any actual numbers, did anyone else notice either a fuzzy signal, or some interference within about 1 Hz of W1AW on 40M? I recorded the entire test run and have been unable to prove to myself exactly where W1AW is; almost any sample of data I select shows two signals within about 1 Hz -- depending on just what segment of the data I analyze, I can sometimes get one peak that is sharper and another that is smeared out over about 0.5Hz, but I'm not confident about which one is the real thing. An FFT with enough bins to separate the two signals loses the CW keying, so I can't use that to see which one is real. Again, nobody post actual frequencies, but if you've looked at the 40M signal very closely, I'd appreciate finding out whether this is local to me, or something others saw. Thanks, John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
I debated whether to stay up and try, but with my lousy antennas I thought the odds of hearing it here in Ohio were fairly small, so I went to bed instead... John Henry Knoepfle wrote: Did anyone hear the west coast station? I and another station here in Tucson did not. Henry On 11/16/06, John Ackermann N8UR [EMAIL PROTECTED] wrote: Hi Bert -- We tend to talk about FMT techniques before the test, and a little bit about propagation, etc., afterwards. But I don't share, and I don't think anyone else should share, results until after the submission deadline on the 15th. After that, it's fair game. 73, John Bert wrote: Hi everyone, Is it common practice to share your FMT results on the time-nuts mailaing list? Or is there pride in trying to be the best of the best (who knows...)? Should we all wait after December 15th...? Cheers. Bert, VE2ZAZ __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
Hi everyone, Is it common practice to share your FMT results on the time-nuts mailaing list? Or is there pride in trying to be the best of the best (who knows...)? Should we all wait after December 15th...? Cheers. Bert, VE2ZAZ __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Did anyone hear the west coast station? I and another station here in Tucson did not. Henry On 11/16/06, John Ackermann N8UR [EMAIL PROTECTED] wrote: Hi Bert -- We tend to talk about FMT techniques before the test, and a little bit about propagation, etc., afterwards. But I don't share, and I don't think anyone else should share, results until after the submission deadline on the 15th. After that, it's fair game. 73, John Bert wrote: Hi everyone, Is it common practice to share your FMT results on the time-nuts mailaing list? Or is there pride in trying to be the best of the best (who knows...)? Should we all wait after December 15th...? Cheers. Bert, VE2ZAZ __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Heard it in Round Rock, TX (EM10) - was considerably weaker than W1AW. Bill (kd5tfd) At 11:47 PM 11/16/2006, you wrote: Did anyone hear the west coast station? I and another station here in Tucson did not. Henry ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT West Coast
Didn't hear anything in Long Beach, CA. or Riverside, CA. from the west coast transmission. Heard W1AW ok though. Doug K6JEY ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
--- John Ackermann N8UR [EMAIL PROTECTED] wrote: Hi Normand -- Your method is similar to mine, except that I use a much closer beat note (usually less than 100 Hz) and use spectrum analyzer software and a sound card to measure the beat note (in the form of the delta between two traces on the waterfall display). Well, you use long term DIGITAL techniques to track probably to the µHz.. i simply use an ANALOG technique to get down to a +/- 10 mHz resolution, and using a higher beat frequency is simply more comfortable to the eye (X-Y scope display). Also, my generator has a 100 Hz resolution, so i can only use 100 Hz multiple beat notes. I think one of the reasons this method works so well is that the FFT effectively averages the signal over some time, and I use a tool in the software to derive an average across all the FFT results. That smooths out the instantaneous variations that make real-time measurement such a challenge. John Maybe some day!! 73 de Normand VE2UM Cheap talk? Check out Yahoo! Messenger's low PC-to-Phone call rates. http://voice.yahoo.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] FMT
I received the following email from the station manager of W1AW. Hi Colin, I didn't want to answer your question too soon. On the days prior to the FMT, I conduct measurements at 1 hour, 3 and 6 hours after initial warm-up. (And of course, this time frame includes the normal broadcast schedule.) From what I can see, the drift on the Orion and Pro IIs is minimal. For example, from the 3 to 6 hour time period (today), the 40-meter Orion drifted 0.12 Hz. The 80-meter Pro II drifted about 0.11 Hz and the 160-meter Pro II drifted about 0.04 Hz. (You have to understand that these three radios are here for evaluation only, and went through their respective Service Departments before we received them.) And just now, I conducted a quick test to see what the real short-term drift would be (given the time frame of the FMT). I didn't notice any significant difference. I'm a little surprised at these numbers. But I have to go on what my counter is telling me. Oddly enough, when we used to run the Harris exciters (during past FMTs), it was not uncommon for me to see at least a 2-4 Hz difference in the 3 to 6 hour time period. So we'll see... Good luck! 73, Joseph Carcia, NJ1Q W1AW Station Manager Interesting...I would not have thought these transceivers were that stable. Colin ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
That's interesting -- from your earlier message, I thought they were still running the Harris exciters for the test itself. It'll be interesting to monitor the drift during the test. My plan is to record audio (W1AW plus my known-frequency marker) of all three bands simultaneously for the whole test period, so if the propagation gods are smiling upon us, I'll be able to look at the beginning-to-end drift. Two of the bands will use HP 3586C selective voltmeters driven from an HP 5065A (using the internal tracking generator as the marker), while 40M will be on an Icom 746 with a PTS synthesizer hooked to the same 5065A providing the marker. The audio from all three receivers is fed into a 4-input Delta44 sound card and recorded as separate .wav files. It's a shame the test wasn't a week or two later -- I just acquired two more 3586Cs on eBay today so I would have been able to use the same hardware for all three bands. That'll have to wait until next year... (I really love the 3586C as an HF measurement machine.) I also hope that by next year I'll have the crystal in the Delta44 slaved to the external reference, and that will remove my last significant source of measurement uncertainty -- though the Delta44 sample rate seems to be very stable even on its own. John Colin Bradley said the following on 11/15/2006 04:37 PM: I received the following email from the station manager of W1AW. Hi Colin, I didn't want to answer your question too soon. On the days prior to the FMT, I conduct measurements at 1 hour, 3 and 6 hours after initial warm-up. (And of course, this time frame includes the normal broadcast schedule.) From what I can see, the drift on the Orion and Pro IIs is minimal. For example, from the 3 to 6 hour time period (today), the 40-meter Orion drifted 0.12 Hz. The 80-meter Pro II drifted about 0.11 Hz and the 160-meter Pro II drifted about 0.04 Hz. (You have to understand that these three radios are here for evaluation only, and went through their respective Service Departments before we received them.) And just now, I conducted a quick test to see what the real short-term drift would be (given the time frame of the FMT). I didn't notice any significant difference. I'm a little surprised at these numbers. But I have to go on what my counter is telling me. Oddly enough, when we used to run the Harris exciters (during past FMTs), it was not uncommon for me to see at least a 2-4 Hz difference in the 3 to 6 hour time period. So we'll see... Good luck! 73, Joseph Carcia, NJ1Q W1AW Station Manager Interesting...I would not have thought these transceivers were that stable. Colin ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Recent radios of that grade all have TCXOs, and that level of performance is really not that hard to achieve today at constant temperature. My Yaesu FT-1000 Mk5 Field (with TCXO) drifts much less than 0.5 Hz at 14 MHz between 30 minutes and one hour after being turned on (in receive), but a couple of Hz during the 1st 1/2 hour (from memory, I did not record the data). I have not tried after continuous, prolonged transmission. I need to retake this data now that I have much better equipment. With regard to accuracy, the rig is about 0.82 Hz low at 14 MHz after warm-up (original factory adjustment, the rig is about 2.5 years old), measured in AM transmit mode, using a 40dB power attenuator on the output driving an HP 5370A counter with 1 sec gate time, with a Thunderbolt GPSDO as external reference. My older Kenwood TS-440S/AT radio (no TCXO, bought new in 1991), drifts about 100 Hz (at 14 MHz) during the 1st 30 minutes of operation (receive) but is quite stable after that ( I did not measure how much, but absolutely no noticeable drift in normal operation, for instance using WWV's zero beat as a reference), regardless of Tx or Rx operation. Didier KO4BB Colin Bradley wrote: I received the following email from the station manager of W1AW. Hi Colin, I didn't want to answer your question too soon. On the days prior to the FMT, I conduct measurements at 1 hour, 3 and 6 hours after initial warm-up. (And of course, this time frame includes the normal broadcast schedule.) From what I can see, the drift on the Orion and Pro IIs is minimal. For example, from the 3 to 6 hour time period (today), the 40-meter Orion drifted 0.12 Hz. The 80-meter Pro II drifted about 0.11 Hz and the 160-meter Pro II drifted about 0.04 Hz. (You have to understand that these three radios are here for evaluation only, and went through their respective Service Departments before we received them.) And just now, I conducted a quick test to see what the real short-term drift would be (given the time frame of the FMT). I didn't notice any significant difference. I'm a little surprised at these numbers. But I have to go on what my counter is telling me. Oddly enough, when we used to run the Harris exciters (during past FMTs), it was not uncommon for me to see at least a 2-4 Hz difference in the 3 to 6 hour time period. So we'll see... Good luck! 73, Joseph Carcia, NJ1Q W1AW Station Manager Interesting...I would not have thought these transceivers were that stable. Colin ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hi Colin -- Actually, the transmitters used for the FMT seem to be very stable and as far as I've been able to observe (during each of the 4 FMTs since they restarted the event) don't drift by a noticeable amount during the test. I'm actually more concerned about the ARRL's measurement setup than I am about the transmitter stability. At least through last year, they measured the frequency off-air by hooking the counter to an outside antenna through a bandpass filter, rather than tapping off the output of the transmitters. With multiple KW signals floating around the vicinity, there's lots of opportunity for counter confusion. Some of us believe that ARRL's frequency measurement of the 160M signal last year was about 0.4 Hz off, and I suspect the measurement setup caused that. John Colin Bradley wrote: I just finished several email exchanges with Joe Carcia, station manager for W1AW, about the operation of the station. I had hoped that the regular daily bulletins broadcast by W1AW would be tightly controlled in frequency, which would allow me to get some practice measuring them. He informed me that they use two IC-756Pro II’s and one Orion I for the transmissions. These radios do not permit the use of external standards for frequency control. Neither do the Harris 3200’s. All of these radios use TCXO’s for frequency control. This setup will be the same used for the FMT on the 15th. They will monitor frequency with a counter hooked to their Z3801. It’s hard to believe, with a 100-watt amplifier in the same case, that these radios don’t drift several cycles during a long transmission. For that reason I would encourage persons making measurements to do so during the specified time for each frequency in question. I think it would be very hard to measure the frequency to 1 cycle or less with the frequency control they use. The West Coast station that will broadcast a 40-meter test signal which will, most likely, be more accurate. That station will be using a Heathkit DX-60 into a 400-watt amp. Frequency control is from a HP-107BR into a HP-5100 synthesizer. While old, this equipment will probably be up to the job. The oscillator is set against GPS and the whole setup will be independently monitored by another station a mile away with a Cesium standard. Colin Bradley ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Personnaly, i use a self-developed technique to remotely measure a station's frequency: I use a precision OXCO controlled RF signal generator to inject an unmodulated (CW) signal (via a directional coupler) signal 1000 Hz below the actual station's frequency (example, to monitor CHU at 7335 kHz, i inject a 7334 kHz signal into the coupler). I then adjust the generator's level to obtain a comfortable 1000 Hz from my receiver (in AM mode preferably, but it even works in FM... do not use SSB or CW modes, since the receiver's BFO will interfere). Finally, i measure the 1 kHz beat's frequency with precision (for that, i use an synthesized audio generator with a ramp (sawtooth) output on an o'scope in a X-Y function (X = ramp, Y = beat). I prefer to use a ramp rather than a sine signal, since the ramp closely resembles a classic temporal sweep in a scope. This way, it becomes very easy to see if the generator's frequency is above or below the beat's frequency, which is much harder with a sine X input. One other way is to use the scope in classic mode with the audio synthetizer (preferably in square wave, but sine would also do the job) feeding the scope's external trigger. However, on distant HF signals, it becomes very hard to precisely measure the station's frequency due to the signal's fading which has important effects on the signal's phase. This phase unstability originates from the constantly changing RF signal's path due to the naturally unstable ionosphere's condition. The receiver does NOT need to be a precision unit (you could even use a VFO controlled radio), since the beat comes from the heterodyning between the station's and the generator's signals. 73 de Normand Martel VE2UM Montreal, Qc. Canada. --- John Ackermann N8UR [EMAIL PROTECTED] wrote: Hi Colin -- Actually, the transmitters used for the FMT seem to be very stable and as far as I've been able to observe (during each of the 4 FMTs since they restarted the event) don't drift by a noticeable amount during the test. I'm actually more concerned about the ARRL's measurement setup than I am about the transmitter stability. At least through last year, they measured the frequency off-air by hooking the counter to an outside antenna through a bandpass filter, rather than tapping off the output of the transmitters. With multiple KW signals floating around the vicinity, there's lots of opportunity for counter confusion. Some of us believe that ARRL's frequency measurement of the 160M signal last year was about 0.4 Hz off, and I suspect the measurement setup caused that. John Colin Bradley wrote: I just finished several email exchanges with Joe Carcia, station manager for W1AW, about the operation of the station. I had hoped that the regular daily bulletins broadcast by W1AW would be tightly controlled in frequency, which would allow me to get some practice measuring them. He informed me that they use two IC-756Pro II¢s and one Orion I for the transmissions. These radios do not permit the use of external standards for frequency control. Neither do the Harris 3200¢s. All of these radios use TCXO¢s for frequency control. This setup will be the same used for the FMT on the 15th. They will monitor frequency with a counter hooked to their Z3801. It¢s hard to believe, with a 100-watt amplifier in the same case, that these radios don¢t drift several cycles during a long transmission. For that reason I would encourage persons making measurements to do so during the specified time for each frequency in question. I think it would be very hard to measure the frequency to 1 cycle or less with the frequency control they use. The West Coast station that will broadcast a 40-meter test signal which will, most likely, be more accurate. That station will be using a Heathkit DX-60 into a 400-watt amp. Frequency control is from a HP-107BR into a HP-5100 synthesizer. While old, this equipment will probably be up to the job. The oscillator is set against GPS and the whole setup will be independently monitored by another station a mile away with a Cesium standard. Colin Bradley ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Do you Yahoo!? Everyone is raving about the all-new Yahoo! Mail beta. http://new.mail.yahoo.com ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hi Normand -- Your method is similar to mine, except that I use a much closer beat note (usually less than 100 Hz) and use spectrum analyzer software and a sound card to measure the beat note (in the form of the delta between two traces on the waterfall display). I think one of the reasons this method works so well is that the FFT effectively averages the signal over some time, and I use a tool in the software to derive an average across all the FFT results. That smooths out the instantaneous variations that make real-time measurement such a challenge. John Normand Martel wrote: Personnaly, i use a self-developed technique to remotely measure a station's frequency: I use a precision OXCO controlled RF signal generator to inject an unmodulated (CW) signal (via a directional coupler) signal 1000 Hz below the actual station's frequency (example, to monitor CHU at 7335 kHz, i inject a 7334 kHz signal into the coupler). I then adjust the generator's level to obtain a comfortable 1000 Hz from my receiver (in AM mode preferably, but it even works in FM... do not use SSB or CW modes, since the receiver's BFO will interfere). Finally, i measure the 1 kHz beat's frequency with precision (for that, i use an synthesized audio generator with a ramp (sawtooth) output on an o'scope in a X-Y function (X = ramp, Y = beat). I prefer to use a ramp rather than a sine signal, since the ramp closely resembles a classic temporal sweep in a scope. This way, it becomes very easy to see if the generator's frequency is above or below the beat's frequency, which is much harder with a sine X input. One other way is to use the scope in classic mode with the audio synthetizer (preferably in square wave, but sine would also do the job) feeding the scope's external trigger. However, on distant HF signals, it becomes very hard to precisely measure the station's frequency due to the signal's fading which has important effects on the signal's phase. This phase unstability originates from the constantly changing RF signal's path due to the naturally unstable ionosphere's condition. The receiver does NOT need to be a precision unit (you could even use a VFO controlled radio), since the beat comes from the heterodyning between the station's and the generator's signals. 73 de Normand Martel VE2UM Montreal, Qc. Canada. --- John Ackermann N8UR [EMAIL PROTECTED] wrote: Hi Colin -- Actually, the transmitters used for the FMT seem to be very stable and as far as I've been able to observe (during each of the 4 FMTs since they restarted the event) don't drift by a noticeable amount during the test. I'm actually more concerned about the ARRL's measurement setup than I am about the transmitter stability. At least through last year, they measured the frequency off-air by hooking the counter to an outside antenna through a bandpass filter, rather than tapping off the output of the transmitters. With multiple KW signals floating around the vicinity, there's lots of opportunity for counter confusion. Some of us believe that ARRL's frequency measurement of the 160M signal last year was about 0.4 Hz off, and I suspect the measurement setup caused that. John Colin Bradley wrote: I just finished several email exchanges with Joe Carcia, station manager for W1AW, about the operation of the station. I had hoped that the regular daily bulletins broadcast by W1AW would be tightly controlled in frequency, which would allow me to get some practice measuring them. He informed me that they use two IC-756Pro II¢s and one Orion I for the transmissions. These radios do not permit the use of external standards for frequency control. Neither do the Harris 3200¢s. All of these radios use TCXO¢s for frequency control. This setup will be the same used for the FMT on the 15th. They will monitor frequency with a counter hooked to their Z3801. It¢s hard to believe, with a 100-watt amplifier in the same case, that these radios don¢t drift several cycles during a long transmission. For that reason I would encourage persons making measurements to do so during the specified time for each frequency in question. I think it would be very hard to measure the frequency to 1 cycle or less with the frequency control they use. The West Coast station that will broadcast a 40-meter test signal which will, most likely, be more accurate. That station will be using a Heathkit DX-60 into a 400-watt amp. Frequency control is from a HP-107BR into a HP-5100 synthesizer. While old, this equipment will probably be up to the job. The oscillator is set against GPS and the whole setup will be independently monitored by another station a mile away with a Cesium standard. Colin Bradley ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
I think one of the reasons this method works so well is that the FFT effectively averages the signal over some time, and I use a tool in the software to derive an average across all the FFT results. That smooths out the instantaneous variations that make real-time measurement such a challenge. What size FFT are you using? What sort of averaging are you doing? What is the bandwidth of the signal you are looking at? How does that compare to the bin size of your FFT? If you are recording the raw data and then post processing the signal, I'd expect you could FFT the whole thing. It has to fit in memory, but that doesn't look like a problem. I think that would get the bin size down to 1/N Hz if you had N seconds of data. (But I'm not a DSP wizard.) If you do that, there is only one sample so there is nothing to average in the time dimension. If the signal is wide enough to end up in several bins, you could average in the frequency dimension. -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hal Murray said the following on 11/10/2006 04:52 PM: I think one of the reasons this method works so well is that the FFT effectively averages the signal over some time, and I use a tool in the software to derive an average across all the FFT results. That smooths out the instantaneous variations that make real-time measurement such a challenge. What size FFT are you using? What sort of averaging are you doing? What is the bandwidth of the signal you are looking at? How does that compare to the bin size of your FFT? If you are recording the raw data and then post processing the signal, I'd expect you could FFT the whole thing. It has to fit in memory, but that doesn't look like a problem. I think that would get the bin size down to 1/N Hz if you had N seconds of data. (But I'm not a DSP wizard.) If you do that, there is only one sample so there is nothing to average in the time dimension. If the signal is wide enough to end up in several bins, you could average in the frequency dimension. The signal is a CW wave. I use a Linux spectrum analysis program called Baudline. It allows me to do a couple of neat things. First is that it can downconvert to improve resolution by decimating and frequency shifting, so I can work with a spectrum maybe 100 Hz wide. Then I run a fairly deep FFT -- I think I used 8192 bins last year. You end up with resolution in the milliHertz, but of course after decimating a bunch and using the deep FFt, it takes 10 or more seconds to fill the bins. I end up with a waterfall display showing the reference and unknown signals over the length of the test. Baudline has another neat tool, which allows you to do an average over length of the waterfall. So, I end up with a single trace that represents the average over the length of the test. Baudline also has a delta feature that will calculate the delta frequency between two signals, so that give me the final output number that I work against the frequency of the known signal to get the result. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
John and I use a similar technique. I am running Windows so I use DL4YHF's Spectrum Lab FFT software. Spectrum Lab will output each line of the waterfall display to a tab delimited text file. Using the function peak_f(f1,f2) I output the frequency of the peak within F1 and F2 to the file. I also output the peak of the signal generator's carrier in a band above or below the band of the desired carrier. The difference between the two is used to calculate the final carrier frequency. You just have to remember to be in the same sideband USB or LSB and on the same side of the signal generator carrier for each measurement in order not to confuse adding or subtracting the delta. At the end of the test the output file contains several lines of data. I import the file into a spreadsheet. The spreadsheet calculates the delta and averages all the readings. I may have several hundred lines of output. As for the audio sample rate and FFT size I have used several the past couple of years. I am sure they are optimal but they work. I am currently running the audio sample rate at 11025 with the FFT size of 32768 with a decimate factor of 2. Bin size is around 168 millihertz. This helps cut down on any CW that may be near the desired carrier as I won't see those signals as they are too fast to fill the bin. For this year's FMT I will use my HP 3586C with its internal tracking generator looped back into its own antenna port (via a step attenuator). This will serve as the signal generator used in the past. A Z3801 feeds the external timebase of the 3586C. It has been interesting to measure the carriers of local AM broadcast and shortwave stations. Our local stations are a few hertz off but WLW (700 KHz) is dead on. I wonder what they are using for frequency control? Mike -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Ackermann N8UR Sent: Friday, November 10, 2006 6:34 PM To: Hal Murray Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FMT Hal Murray said the following on 11/10/2006 04:52 PM: I think one of the reasons this method works so well is that the FFT effectively averages the signal over some time, and I use a tool in the software to derive an average across all the FFT results. That smooths out the instantaneous variations that make real-time measurement such a challenge. What size FFT are you using? What sort of averaging are you doing? What is the bandwidth of the signal you are looking at? How does that compare to the bin size of your FFT? If you are recording the raw data and then post processing the signal, I'd expect you could FFT the whole thing. It has to fit in memory, but that doesn't look like a problem. I think that would get the bin size down to 1/N Hz if you had N seconds of data. (But I'm not a DSP wizard.) If you do that, there is only one sample so there is nothing to average in the time dimension. If the signal is wide enough to end up in several bins, you could average in the frequency dimension. The signal is a CW wave. I use a Linux spectrum analysis program called Baudline. It allows me to do a couple of neat things. First is that it can downconvert to improve resolution by decimating and frequency shifting, so I can work with a spectrum maybe 100 Hz wide. Then I run a fairly deep FFT -- I think I used 8192 bins last year. You end up with resolution in the milliHertz, but of course after decimating a bunch and using the deep FFt, it takes 10 or more seconds to fill the bins. I end up with a waterfall display showing the reference and unknown signals over the length of the test. Baudline has another neat tool, which allows you to do an average over length of the waterfall. So, I end up with a single trace that represents the average over the length of the test. Baudline also has a delta feature that will calculate the delta frequency between two signals, so that give me the final output number that I work against the frequency of the known signal to get the result. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FMT
Hi Mike, Interesting, I was just doing pretty much that, except that I did not think of using the tracking generator of the 3586A as a reference, I used an 8657B synthesizer phase locked to the Thunderbolt GPSDO to inject a reference signal 20Hz above the test signal (I used WWV at 5 MHz for test), so that I could display both signals at the same time in the FFT using Spectrum Lab. Setting the two very close eliminates the risk of selecting the wrong sideband and reduces the error caused by the sound card sample rate being off. I found out using the slowest sampling rate (5 kHz or so) and the largest FFT size seems to give the best resolution (10 mHz?) and good filtering (several seconds of time constant). I also set the software to display one bin per pixel. There is a screen plot of Spectrum Lab with the 2 signals on my web site http://www.ko4bb.com/Test_Equipment/SpectrumLab.png Exporting the data to a file and using a spreadsheet to do the post processing is a good idea, thanks. To display the generator frequency using the peak function, I simply disconnect the antenna, which causes the generator to be the largest signal. I intend to do that a few times during the test to make sure everything is stable. I have not found out how to export data to a file so that it includes the peak, but I'll be looking (I started using Spectrum Lab a couple of weeks ago and there are a lot of settings I am not familiar with yet)... If I don't find soon, I may send you a message :-) I am interested also in finding how you can output two peaks (signal under test and generator) to the log file. It's interesting to look at the peak on WWV and see it wobble at the rate of the fading (or close). During a few minutes of observations, the frequency was about 0.5 Hz low and it fluctuated by about 0.4 Hz peak to peak with a period of a few seconds. I only have an 80m antenna at the moment (quarter wave slopper hanging from the 50 feet tower), so that will be the band where I will have my best shot. I may try 40m as east coast signals tend to be good on the 80m slopper, in spite of the severe mismatch. Didier KO4BB Mike Suhar wrote: John and I use a similar technique. I am running Windows so I use DL4YHF's Spectrum Lab FFT software. Spectrum Lab will output each line of the waterfall display to a tab delimited text file. Using the function peak_f(f1,f2) I output the frequency of the peak within F1 and F2 to the file. I also output the peak of the signal generator's carrier in a band above or below the band of the desired carrier. The difference between the two is used to calculate the final carrier frequency. You just have to remember to be in the same sideband USB or LSB and on the same side of the signal generator carrier for each measurement in order not to confuse adding or subtracting the delta. At the end of the test the output file contains several lines of data. I import the file into a spreadsheet. The spreadsheet calculates the delta and averages all the readings. I may have several hundred lines of output. As for the audio sample rate and FFT size I have used several the past couple of years. I am sure they are optimal but they work. I am currently running the audio sample rate at 11025 with the FFT size of 32768 with a decimate factor of 2. Bin size is around 168 millihertz. This helps cut down on any CW that may be near the desired carrier as I won't see those signals as they are too fast to fill the bin. For this year's FMT I will use my HP 3586C with its internal tracking generator looped back into its own antenna port (via a step attenuator). This will serve as the signal generator used in the past. A Z3801 feeds the external timebase of the 3586C. It has been interesting to measure the carriers of local AM broadcast and shortwave stations. Our local stations are a few hertz off but WLW (700 KHz) is dead on. I wonder what they are using for frequency control? Mike ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
