[evlatests] Changing P-band Dipole orientations

[Rob Long]

What Rick mentioned is correct. Unfortunately, it is difficult to keep 
the dipole aligned "perfectly", dependent on which direction the 
sub-reflector was last rotating. There are nylon guide blocks at the 
apex of the antenna trombone assembly which do loosen/wear over time and 
allow more slop in the dipole orientation. CCW vs CW rotation of the 
sub-reflector can leave the dipole in slightly different positions. 
Usually, this is within a couple of degrees.


Rob


On 9/11/2024 10:12 AM, Rick Perley via evlatests wrote:
> I noted yesterday some discrepant dipole orientations, and noted that 
> I had the impression these were worse than at earlier times.
>
> By happenstance, I'm calibrating some old (2019) P-band data for Tracy 
> Clarke, which allows me to judge the correctness of that statement.
>
> The statement is *wrong*.   Misorientations were worse in 2019 than now.
>
> Tracy's data were taken twice – in March and in September of 2019.  
> The distribution of orientations were in fact worse than now, and also 
> were very different.  Antennas misoriented now were better (or worse) 
> in 2019.  Indeed, the correlation between the two 2019 observations is 
> not very strong.
>
> I believe these conclusions are not surprising, as the dipoles are 
> known to be subject to rotation caused by the rotating subreflector.  
> Perhaps Rob Long can confirm this statment.
>
> Rick
>
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