[evla-sw-discuss] OSRO OPT - Sampler Outputs and Subbands

[Barry Clark]

> On the OSRO page Table 1 is used for full polarization setups in which there are two independently tunable subbands.  It is not stated whether or not the bandwidth can be selected independently for each subband, or whether a single BW is chosen and used for both subbands.
> 
> Should the OSRO user interface of the OPT permit selection of a BW for each subband?


Yes.  This is a very useful mode - people use a narrow band for a maser
used as a phase calibrator, and a broad channel to look at the continuum
emission around it.


>    1.  Will we display a discrete set of valid values or allow users to type in values?
> 
>    2. One second is given above as a minimum time.  Should we nonetheless allow input of values < 1s and issue a warning, or truly prohibit it?

I'm in favor of prohibiting it - it is too onerous to explore what the
real limits are, and we should prevent people from getting clobbered by
stuff we haven't gotten around to finding out yet.

> This works well except in Ka band.  In Ka the A/C IF goes only as low as about 32GHz.  This means w/ the approach of putting each subband in a different sampler output we cannot support certain requests (eg, subbands at 28GHz and 29GHz).  Of course, we could put such combinations in the B/D pair, but only one of these can then be Doppler tracked.

I'd favor giving people two basebands only, and if they want to park
both below 32, tough.