kuze...@gmail.com said: > ... I would presume that the fixed location used for above calculations > would be relative to the position of the antenna?
A side effect of figuring out where you are is figuring out when you are there. There are 4 unknowns: X, Y, Z, T, so you need 4 equations. You get one equation from each satellite so you need 4 satellites. If you assume you are on the surface of the earth, you can get away with only 3 satellites. Yes, that tells you where the antenna is located. If you know where you are, you only need 1 satellite to get the time. > I read somewhere that even compensating for the length of the > antenna cabling is important? > Wow. Okay. The user manual actual considers this cable delay to be worth > mention? Sure. The speed of light in air/vacuum is 1 ft/ns. Coax (and fiber) is slower. Junk coax is roughly half as fast. Good coax (foam) is roughly 2/3rds as fast. So it's easy to get 100 ns but unlikely to get more than a microsecond on an amateur budget. Whether that is important for you depends upon your application and the length of the antenna cable. With a modern not super-expensive scope, it's easy to see 1 ns offsets, so cable lengths could be important on something as simple as comparing the PPS outputs from 2 GPS systems. Don't forget to consider the lengths of other cables in your setup. I remember getting an interesting lesson in this area many years ago. We had a couple of scope probes with long cables. I was using one long one and one normal one and looking at high speed digital signals. The offset was enough to confuse me. -- These are my opinions. 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.