[evlatests] L302 doppler tracking

[Rob Long]

Sorry, I thought I had hit reply all!

The phase jump is not 180d as I first thought. Measurements indicate 
that when cpol changes from 1 to 0 (mpol also changes from 1 to 0) there 
is an approximate 149d phase jump.

When cpol changes from 0 to 1 (again mpol changes from 1 to 0), I see an 
approximate 24d phase jump. When mpol changes without cpol changing, it 
varies slightly but is less than 10d (usually between 3 to 6).

I need to look more carefully at the transition boundaries to determine 
if this is consistent on all 128 comb line tunings and determine exactly 
which components in each loop contribute.

Rob