Hi As you get into a bigger array, your antenna pointing / tracking requirements become more exotic. I doubt that your 8 X array antenna has to do much more than track the moon, I could be wrong ….
Bob > On Nov 17, 2017, at 8:14 PM, Azelio Boriani <[email protected]> wrote: > > 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 <[email protected]> wrote: >> Hi >> >> >>> On Nov 17, 2017, at 4:26 PM, Patrick Barthelow <[email protected]> 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 <[email protected]>[email protected] >>> >> >> 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 -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
