[evlatests] Oddities at L-band (pointing, Tcal, Tsys, Psum, etc.)

[Barry Clark]

On 08/13/2013 10:05 AM, Rick Perley wrote:

[snip]

>      3) I used a central subband (#8 -- 1480 MHz, nice and stable) to
> look at the PSum values.  They should all be reasonably close to each
> other if 'set and remember' is working right.   I'm prepared to accept
> that 'reasonably close' means with 50% of some median value.  But this
> is not the case.  The median value for the subband appears to be about
> 10 counts.  In LCP, all antennas are within 50% of this.  But in RCP,
> there is a very different story:  ea02R, ea07R and ea13R are all at 1
> count, or less!  That's a factor of 10 too low!!!

What do the Psums in the other subbands do?  If there is a lot
of interference in some subband, you could have big numbers there
that make the average Psum sensible.  If not, it could be that
the wire between the T304 detector and the sampler has a lot of
attenuation.  Do both polarizations do this?

[snip]


>      5) In perusing the Tcal tables, some curiosities are found:
>
>      a) ea07 has a Tcal about 8K -- 5 times higher than any other
> antenna!  Is this right?

Right or not, that's what the Soida documents say.

>      b) ea11, ea14 and ea17 all have incredibly high Tcal values listed
> for the first two subbands (values exceeding 55K for ea11!!!), but
> normal (1.5K) values for all other subbands.  Can this be real?  I
> didn't think the noise diodes could have output powers 30 times higher
> than the mean in the bottom 200 MHz of the band...

This is due to the (ahem) feature that the Tcal stowed in the SDM
is the interpolation to the subband reference frequency (lower
edge) combined with the fact that the bandpasses of these receivers
appear to go really whacky below about 1150 MHz.