On Mon, 19 Jun 2017 08:52:37 -0400 Dan Kemppainen <d...@irtelemetrics.com> wrote:
> So, what sorts of things are done for high precision survey work? I > would guess a sturdy mount, good sky view, no reflections, good antenna, > no nearby radiators, etc. Those all seem like common sense stuff. I don't know about survey work, but you can have a look at the EUREF[1] stations. Most (all?) stations in the list[2] have pictures. [1] https://en.wikipedia.org/wiki/EUREF_Permanent_Network [2] http://www.epncb.oma.be/_networkdata/stationlist.php > But for applications that really matter, what sorts of things might be > missing above. Obviously, really expensive silly things won't be done on > my site for a few GPSDO's, but it would be good to know what the issues > are. You try to mount the antenna as sturdy as possible. The best is if you have an open and level field and can put a nice block of concrete on unmoving bedrock. If not, ontop of a well build building will do, though the vibrations might not be negligible. People use also relatively low towers (high towers tend to vibrate), of only 2-5m height. Again mounted on a block of concrete, if the tower isn't itself a construction made of concrete. The dome should be such, that you don't get a bird problem and that snow does not stick. At the same time the dome should be shaped in a way that does not cause any refraction. If your reference station (which is in a nearby building in a temperature controlled room) has any ultra stable reference oscillator (think of a Cs beam standard or a hydrogen maser), then you also want to have the temperature and humidity of the cable going to the antenna controlled. Ie. you put the antenna cable into a tube and blow constant temperature/humidity air through it. Of course you can go even more crazy, but the temperature/humidity controlled cable is about the most extreme I have heard of. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ 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.