[daip] AVSPC, IFs

[Gustaaf van Moorsel]

I am unclear about the exact meaning of IF specification in
AVSPC.  I have a spectral line data set of 7 channels and 2
IFs at different frequencies.  I'd like to create a pseudo
continuum using channels 2 through 6.  I am not sure how to
specify ICHANSEL.  I tried various combinations:

ICHANSEL

2,6,1,2
2,6,1,1
2,6,2,2
2,6,0,0

First of all, all resulted in an output data set with 2IFs,
also the runs where only one IF was specified.

Second, all *except* 2,6,2,2 appear to give the same results.
Running AVSPC with 2,6,2,2 gave the same results only for IF 1,
but different values in IF 2.  Moreover, whereas in all cases
except 2,6,2,2 the bandwidth for both IFs was 15625 kHz, for
2,6,2,2 it was 15625 only for IF1, but 9375 for IF 2.

Since on our EVLA web page we are advertising using AVSPC to
create a pseudo continuum I am sure we are going to get asked
the same question.

Thanks for your advice in this matter,

Gustaaf