[daip] AIPS BPASS

[PAUL]

Hi,

I was just wondering if someone could tell me what bpass actually does?

I've used AIPS many times before to reduce VLA data and had no problems.
I'm currently working on GMRT data in which the bandpass seems quite  
variable.

I have 128 chans @ 610MHz and running BPASS before CALIB means I get  
100% good solutions.  However, if I run CALIB without any BPASS, I  
get a very high failure rate (~90% bad solutions) - even with the  
specified UVRANG's for my calibrators from the VLA calib manual,  
WEIGHTIT=1 and WTUV=0.1 for stability (both solmod='A&P' and soltype  
'L1R').

However, I think the AIPS cookbook suggests using BPASS after CALIB  
and not before.  I've tried averaging channels together using SPLAT  
(with aparm(3)= 1 and CHANNEL=10 for example) but this only helps  
slightly in getting better CALIB solutions.

Also - I've noticed that BPASS actually changes my UVPLT's quite a  
bit (i.e. the difference in bparm 0 (aplitude .vs. BL)  is quite  
different when I toggle DOBAND between -1 and +1.

I'd be extremely grateful for any advice you can offer,

thanks in advance,

Paul