VEGAS / DIBAS Potential Upgrades

OTF Mapping Problem

Ray

Git Repository

Jason

IF Modules

Galen

• Split dual-channel modules into single channel modules to improve channel-to-channel isolation
  • Required removal of internal noise source
  • Improved isolation to >70 dB
• Removed Noise/Tone couplers and Monitor Out Couplers to improve in-band response
• Reduced overall gain by 12 dB to better match gain between GBT-IF and VEGAS ADC's
• Simplified IIc interface and commands

Spectral Line

ADC calibration

Paul Marganian

BOF files

Randy and Jason

Dealer / Player fixes

• VEGAS sets the ACC_LEN keyword in shared memory, which the HPC uses for the GPU accumulation length. DIBAS does not set this keyword in LBW modes. This is required, and should be straightforward to add via the dibas.conf file.
• In VEGAS, we modified the parameter calculations to be more precise with respect to the LBW modes, including how blanking was programmed. This does not exist in DIBAS.
• Pulsar BOF network interface names have been standardized. DIBAS uses the old naming scheme.
• Changes required to support power monitor?

HPC Software

Joe and Ray

• There is no subband limiting capability in DIBAS. The player/LBWBackend.py code does not allow values other than 1 or 8, and the code to snip out subbands is not implemented in the fits writer.
• There is no normalization code in the dibas fits writer.
• There are no ADC calibration keywords in the dibas fits writer.
• Currently DIBAS fits writer will produce more data than requested by rounding up to a whole number of integrations. The HPC now blanks the data beyond the end of a scan. This means there will be a slight change in functionality.
• The definition of stt/stp fields has changed in LBW modes. Previously these were not really useful in LBW mode, because they omitted the counting of blanked accumulations. These fields now operate like they do in HBW, where they are a count of accumulations (blanked or not). These are really debug columns, so I don't think this is even an issue.
• The guppi_daq has integrated the GPU change to allow increased bandwidths. (Not an issue, but not included in the deployed DIBAS.)
• The DIBAS spectral line FITS writer does not contain the spike table of vegas.

Pulsar

Existing BOF file changes

Randy and Jason

Potential New BOF Files

RMP to look at the list

HPC software

Ray to see whether Paul's fix is merged back in

-- RichardPrestage - 2015-09-22