[evlatests] Which antennas should we connect to WIDAR-0?

[Michael Rupen]

Hi Mark,

> Note that the 9-antenna restriction to WIDAR-0 you discuss
> below really applies only in Aug when deformatter limitations
> will set the number of sub-bands to 9x4=36. But prior to that,
> we can certainly connect 10 antennas to WIDAR-0, with limited
> sub-bands (e.g. we could connect 10 antennas with 2 sub-bands
> each in Jun as we originally planned).
>

OK, we're all getting confused here I think.  Doug just told me we have
more than enough demuxes and deformatters to support the initial WIDAR-0,
so Mark is right on that; but his argument about subbands is misleading.

1- In the short term (until the fall) the number of antennas available
   to WIDAR-0 is limited by the number of Station Boards.  Doug assures me we
   have enough demuxes and deformatters (once we've stripped the PTC) to
   support the full 11 StB we'll get by the end of March or so; the next
   big set of StB isn't due until the summer.
   - Note that we will be running with one or two StB per antenna, until
     late summer or early fall.   We need one deformatter per StB, so we
     only need 20 or so until the fall.  At that point we need 4 StB per
     antenna and run into the 9-antenna limit set by the number of
     deformatters.
   - Each StB can handle either 1 x 1 GHz (single pol'n) with an 8-bit
     sampler, or 2 x 2 GHz (dual pol'n), with 3-bit samplers.

2- The bandwidth we obtain with WIDAR-0 is limited by the number of Baseline
   Boards, not the number of Station Boards, until we get a LOT more BlBs...
   which isn't until the fall.  So the number of available subbands
   has nothing to do with the number of deformatters, until that point.
   - By May we should have 10 BlBs, corresponding to 5 subband pairs or
     a maximum bandwidth of 5 x 128 MHz= 640 MHz.  This is < 1 GHz so
     we only need 1 StB per antenna for single pol'n, or 2 StB per antenna
     for both pol'ns.

Whew!

To summarize:  We have enough hardware for 8 antennas now, and will
have enough for 3 more antennas once we've refurbished the Station Boards
in the PTC (i.e., in late March).

All perfectly clear now, eh?

             Michael