[time-nuts] Difference in GPS antennas

[John Green]

Mark Sims wrote:The quality of the results match the quality of the antenna.
 A geodetic/survey grade antenna gives results to within a few inches.  A
conical timing antenna within 8 inches.  A cheap patch antenna around a
foot.
I took one of those conical timing antennas apart only to find that it has
the same ceramic patch as most cheap GPS antennas. How is a survey grade
antenna different? I would like to be able to know one when I see it.