Quite true. One of my other interests is the ionosphere and propagation. This of course has an effect on GPS and other time related receiving systems. In support of my monitoring and trying to measure such things I monitor on a more or less continuous basis CHU on 7850 KHz. This in itself may not seem that unusual except that I am about 20 miles from the CHU transmitters and I monitor this transmission with the idea of creating a dopplergram of it's signal. As we know, HF radio signals are reflected and refracted by the various layers of the ionosphere. In doing so the signal can exhibit apparent changes in frequency due to the continual movement of these refracting and reflecting layers.
My advantage being so close to the transmitter is that I also receive the ground wave of these signals which are not reflected or refracted in any way. I have a receiver set up which feeds Spectrum lab running in a long integration mode and displaying a very narrow bandwidth of just over 3 and half Hz. I publish my dopplergrams to a dropbox web page here: https://www.dropbox.com/sh/9dakbbrrn2ju3hc/TIIKrDY-Iu usually stored by month these: https://www.dropbox.com/sh/9dakbbrrn2ju3hc/AAA7FLx2nZuEZzBayIqyMAUza/20140320 are for April 20 this year. The solid line more or less in the center of the image is the ground wave from the CHU transmitter on 7850 KHz, everything else is the Doppler shifted signal as it has been reflected and refracted by the various continuously moving layers of the ionosphere. You will note that sometimes there is more than one predominate Doppler shifted signal. Variations in the more or less solid line in the middle of the images is the result of drift in the local oscillator in my receiver. It is not currently locked to GPS. However, as Tom has suggested it makes a good thermometer as it is a relatively high stability oscillator but temperature variations in my lab show as minor changes in these images. I have in fact done a reasonable calibration and I can tell at glance the approximate temperature of my lab near this radio as well as when the furnace has started in the colder months or when the air conditioner starts in the warmer months. There is a group in Czech Republic doing something very similar: http://ok0eu.fud.cz/ They are using their own network of GPS disciplined transmitters on 80M and monitor their signals in a similar fashion. They describe their studies as also studying the effects of gravity waves. Along the lines of trying to measure and study the ionosphere using these dopplergrams, I have also toyed with the idea of trying to make my own passive sounder. There is a network of ionospheric sounders in the Canadian Arctic called CHAIN - Canadian High Arctic Ionospheric Network. They use GPS receivers to measure characteristics of the ionosphere such as total electron count (TEC) by monitoring phase scintillation of the GPS signals. They are using modified GPS's with high stability reference oscillators. I don't know yet if any of my GPS receivers would provide any useful data even with a high stability reference but the thought occurs that there might be another way indirect way. DGPS beacons transmit corrections for GPS users and something I stumbled across on another web site suggested that some of this data may be buried within the corrections provided by these DGPS beacons. And it so happens that I have a DGPS nearby which I can receive easily and reliably 24 hours a day but I just haven't got round to doing much more than brainstorming and trying to understand just what I need to do to connect the dots. For reference, this is the web site and blog posting were I stumbled across the idea of using DGPS correction data: http://goughlui.com/?p=1071 I have not been able to connect all the dots between all these subject but I am getting there. At least it is fun and educational trying. After all, it's the journey which is brings the greatest rewards, not the destination. Cheers, Graham ve3gtc -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: June-24-14 3:35 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Loran, GPS, Lightning, Timing > I am seriously considering involved as I am a bit of a weather nut too. I suspect this is quite common. You don't have to get into precise time very deep before you realize that all your timing gear is just pile of environmental sensors in disguise. Before time-nuts began, the first timing guy I met was Doug Hogarth (www.niceties.com) and he was seriously into weather measurement. He later got into the world of ultra-precise weight (mass) measurement. So I guess time-nuts is just a subset of measurement nuts. A quartz oscillator makes a good thermometer and sometimes a hygrometer and barometer too. An OCXO is a sensitive anemometer (just ask anyone who uses a PWM fan for TBolt temperature control). Quartz also makes an excellent accelerometer, gravimeter, tiltmeter, or even seismometer. An OCXO with EFC is a good voltmeter. Atomic clocks are superb magnetometers. And as Einstein predicted, atomic clocks make good altimeters and speedometers too. So everything we play with is a sensor. It's no wonder we are preoccupied with environmental sensing. Maybe Time is just what's left over after you shield or attenuate or compensate for everything else. /tvb See also: Quartz Resonators vs Their Environment: Time Base or Sensor? http://dev.quartzdyne.com/pdfs/quartzresonators.pdf http://www.paroscientific.com/ This electronic message, as well as any transmitted files included in the electronic message, may contain privileged or confidential information and is intended solely for the use of the individual(s) or entity to which it is addressed. If you have received this electronic message in error please notify the sender immediately and delete the electronic message. Any unauthorized copying, disclosure or distribution of the electronic message is strictly forbidden. NAV CANADA accepts no liability for any damage caused by any virus and/or other malicious code transmitted by this electronic communication. 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