The software I use can only measure time to the nearest 1 msec. This means that at times I am getting different pulse repitition interval indications when I measure between any two single pulses. For example sometimes I am measuring 44 msec and other times I am showing 43.

Measurements across multiple pulse groups and deviding by the number of pulses has consistantly shown a PRI of about 43.66. For example in this particular shot the arrow on the right points to a leading edge pretty solidly at 2548 msec. The arrow on the left points to a leading edge that is between 1980 and 1981. There are 13 pulses between those two points. 2548 - 1981 yields 567 msec. 567 msec devided by the 13 pulses yields a PRI of 43.62 msec. If you use the 1980 msec number for the left side you get 568 msec. Devided by 13 pulses that yields a PRI of 43.69 msec.

The actual value of the PRI is then between 43.69 and 43.62 msec.