The antenna cables have what we call two wraps. Starting from due south, the antennas can slew 265 degrees in azimuth in either direction. The right wrap is clockwise, and the left wrap is counterclockwise. The wraps overlap outside the azimuth range of 85 - 275 degrees (true).

The OBSERVE program *assumes* that the antennas are pointing due south (ie. 180 degrees (true) in azimuth) at the beginning of any observing program. So if your first source is anywhere in the azimuth range 85 degrees (true) rotating southward to 275 degrees (true), there is no wrap problem because the wrap is unique. If your first source is anywhere in the north (that would mean anywhere outside the range 85 - 275 degrees (true) azimuth), OBSERVE picks the shortest path to that source, and you end up on the best wrap. The wrap cards ensure that the antennas actually get to that wrap at observation time. Without a wrap card, the on-line system will always assume a CCW (left) wrap. However, sometimes that is not the "best" route as determined by the OBSERVE program. There is the possibility that data will be lost as the antennas spend time unwrapping if the best wrap is not chosen by the online system.

The antennas slew at a rate of 20 degrees/minute in elevation and 40 degrees/minute in azimuth.

Below are two examples of antenna wrap cards. (ADR=Right Wrap, ADL=Left Wrap)

1331+305      18 12 40 13 31 08.2873 +30 30 32.959C    CC   C   0000   7.47

//AN                                                                  ADR 



0137+331      20 13 03 01 37 41.3051 +33 09 35.394C    CC   C   0000   5.60

//AN                                                                  ADL