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EVLAnotes.txt
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EVLAnotes.txt
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This is the version on noatak. I don't have my laptop with me today
to work on the version on it. Jan 4, 2013.
Each "stream" must come from a separate IF.
1 GHz IFs. 128 MHz chunks inside that.
11 MicroHz tuning granularity. So can ignore.
The stream is always upper sideband.
Crossovers are about 1/16 of band wide.
Eventually the narrow bands are arbibrary positions in the 128 MHz
But for now, treat it like a PFB - "snap to grid"
IF names in pairs.
Jan 4, 2013 So far, only using A, B, C, and D. Assume that means
the 8 bit samplers. Ok?
A0/C0 8bit
B0/D0 8bit
A1/C1 3bit
B1/D1 3bit
A2/C2 3bit
B2/D2 3bit
... ...
No phase application across observing bands. enforce?
Parse intents
Parse intents and warn if not recognized.
Keep VLAMODE as is and put in an intent.
Deal with pointing.
Put request into an intent. But keep old infrastructure.
For reference pointing, using interferometry so don't use same
sources as the VLBA.
Added at meeting Sept. 13, 2012
4 streams
MARK5C on VLBA stops the recorder every scan. No longer need inhibition
against long recording scans?
Several short scans in a row are needed for phasing as phase is only
applied at end of scan. These short scans should not show up on the
VLBA schedule as VLBA scans. But the user should have control of the
lengths of the short scans ("subscans").
VLAPSCAN phasing subscan length. Pass through VEX file to VLA.
INTENT="VLA:PHASE_SUBSCAN=10"
First scan on a phase up source must have no phases applied (not even from
previous phasing).
VLA always net upper sideband. Make sure that is clear in the VEX file
and the bookkeeping is ok.
Maybe include the receiver name in the if_def.
Include pointing scans as with other antennas.
Pointing scans need to be 2.5 minutes. Identify in VEX file by
lack of a phasing intent and a drive number 0 (no record).
Just specify frequency and bandwidth.
Don't worry too much about which IF names are used.
If there are more than 2 IFs, keep A and C higher than B and D.
Always say A and C if there are only 2 IFs.
Main new thing needed now is the subscan specification for pointing
scans.
Jan. 13, 2013
Thinking about generalizing freq.dat. Try to handle continuously
tunable LOs and separately tunable IFs (multi band (eg S/X) or multi
IF in one band (eg. 6cm, wide X).
Current freq.dat entries (ignoring old VLA)
VERSION
STATIONs
NAME
NOTE
PRIOrity
IFNAME
ALTIFN
RF1
RF2
LO1
FE
POL
SYN
DUALX
LCP50CM
RCP50CM
CH1RF1 (for 2cm filter)
CH1RF2 (for 2cm filter)
Additions for tunable LOs and multiple settings.
IFLO Low end of usable IF (512 on RDBE)
IFHI High end of usable IF (1024 on RDBE)
LO1 Low or only FIRSTLO
LO2 High FIRSTLO or 0.D0 if it's fixed.
IFSIDE
For VLBA, might have a fixed FE3
LO1EQN Recognized options: (fe1+fe3, fe2+3*fe3, fe1+6*fe3)
IFMATCH Must share LOs with this IF.
For DUALX:
Normal X band IF B would have IFMATCH = ' ' (eg any)
IF D LCP would have IFMATCH = B
IF D RCP would have IFMATCH = ' '
That forces dual pol to share LO, but not
2 RCPs.
Most bands IF A would have IFMATCH C (RCP)
IF B would have IFMATCH D (RCP)
IF C would have IFMATCH A (LCP)
IF D would have IFMATCH B (LCP)