With 197dB of path attenuation and, say, 1W or 2W of transmitter power, I think that a modest antenna is insufficient. The usual yagi array for this distance is made by 8 27-element antennas like this: <http://ok1teh.nagano.cz/dl5fn.jpg>
On Sat, Nov 18, 2017 at 12:54 AM, Bob kb8tq <kb...@n1k.org> wrote: > Hi > > >> On Nov 17, 2017, at 4:26 PM, Patrick Barthelow <apollo...@gmail.com> wrote: >> >> From me, Pat a newbie, second post: >> >> A new project, STEM opportunity. A STEM/CitizenScience/Ham Space Science >> project. Kids welcome. >> In formative stages so this is for internal discussion, not for public >> announcements yet. >> Will do a frequency measurement of a Cubesat at about 437 mhz that will >> orbit the Moon in 2018. >> Can be received by modest yagi antennas while orbiting the moon. > > That sounds like a pretty high ERP … Of course your definition of a modest > antenna > may not be quite the same as mine :) Consider that there *are* SNR > implications > when you get into your accuracy requirements below. > >> Challenge is to get/use/build precision frequency references and counters, >> and measure the carrier frequency. Cesium, Rubidium, MASER, GPS based, >> commercial standards, and their derivations all welcome. >> Have found 4 (and More) more hydrogen line masers in diverse locations >> around the world, who wish to participate. >> USA, Netherlands, South Africa, Australia, Mexico, and other locations have >> expressed interest. >> >> I am a member of Team Alpha Cubesat. We and some other teams are in the >> NASA CUBEQUEST challenge. Launching next year a 6u cubesat to lunar >> orbit. I am not an expert at the freq measurement aspect of this, so, I am >> a Newbie. With tons of questions, but I was surprised how quickly a check >> of the world's Hydrogen line MASERS got many to offer to come on board. >> MASER is overkill, but that is OK. > > The MASER is a cute device. It is not an accurate device by it’s self. It is a > very *stable* device. Yes, that is a subtle distinction. In this case I think > it is > a pretty important one. > >> The Chief Scientist of the project is >> in the USA and wants to make measurements to the HZ level, at 437 mhz so >> with MASERS and Cesium, Rubidium we are overkill but it could generate >> STEM/Citizen Science participation. That is what we are doing. So the >> satellite will be on 437.5 mhz plus minus doppler. We have to measure >> its received freq to 1 HZ or less. > > Ok, 1 Hz at 437.5 MHZ is roughly 2 ppb. That is pretty much “slam dunk” > accuracy > with a GPSDO. Much easier to obtain and set up in a school environment. The > key will be orbit estimation for the +/- doppler part of it. Orbit > estimation is not > quite a slam dunk sort of thing. The GPSDO would also give accurate location. > Even with good orbit data, the solution still requires a good location > estimate. > >> So I talked to the chief scientist, >> and we decided to go with a public STEM related program > > I’ve been down the road (from scratch to running) on STEM competitions. The > KISS principle is one to keep in mind. At the same time you *do* want a topic > that presents a challenge. > >> with it. [PLEASE >> DO NOT GO PUBLIC YET > > This *is* a public list, it’s “out” now. > >> this is confidential for now.] Announcement of a >> competition for anyone to measure the frequency of the sat as it is in moon >> orbit. So I decided to check with about 5 geographically diverse located >> MASERS. ( Australia, South Africa, UK, Holland, Mexico and USA, and got >> or am getting buy-in from them to make the measurement. I was surprised >> they did not just say go away... a half million dollar MASER is, or should >> be busy with similar but necessary measurements from paying customers. >> Overkill, I admit, but it is a chance for Citizen Science publicity, >> Popular Science, STEM, etc.. >> >> >> Anyway I got a bunch of MASERS to participate and will develop a website >> for people to measure the freq and send in their "answer". We will have >> (are looking for) sponsors that will pay prizes or wall paper awards, for >> very close accurate measurements. >> This is like a modern day Frequency Measurement Test that ARRL did years >> ago. I will in fact call ARRL to see if they want to play in this. I will >> CC others to see if they want to play. Other frequency references used may >> be commercial variations of >> Cesium Beam and Rubidium references. But the King Kong in accuracy is the >> MASER. I got to learn a bit about the MASER they had at Arecibo when I was >> there. And now know a school in Europe a Technical Instrumentation >> school, that offers a project to build a Hydrogen Line Maser using modern >> simpler, cheaper methods and hardware. >> >> Arecibo may play on this event next year. So, you only need modest yagis >> to pick up the Sat at moon distances on 437.5 mhz should be fun... >> The Goldstone MASER; above: >> >>> >>> https://www.nist.gov/pml/time-and-frequency-division >>> https://www.nist.gov/pml/time-and-frequency-division/radio-stations/wwv >>> http://tf.nist.gov/stations/wwvtimecode.htm >>> https://www.nist.gov/pml/time-and-frequency-division/time-se >>> rvices/history-radio-station-wwv >>> >>> https://www.nist.gov/pml/time-and-frequency-division/time-se >>> rvices/wwv-and-wwvh-digital-time-code-and-broadcast-format >>> >>> http://tf.nist.gov/phase/Properties/main.htm >> >> See/Search Also: >> Precise Time and Time Interval Clocks Time Frames and Frequency, James R. >> Clynch Navy Postgraduate School. >> Introduction to Frequency Standards by Lindon Lewis >> >> >> Interested? Get back to me to start planning for the 2018 launch, and >> cubesat in lunar orbit, exact date not known. >> >> Best, 73, Pat Barthelow AA6EG >> apol <apollo...@gmail.com>lo...@gmail.com >> > > Bob > >> >> *"The most exciting phrase to hear in Science, the one that heraldsnew >> discoveries, is not "Eureka, I have found it!" but:* >> "That's funny..." ----Isaac Asimov >> <masergoldstone.jpg>_______________________________________________ >> 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. _______________________________________________ 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.