Attached is a sample file set for a Mark5B data format project.  The VLBA 
currently uses Mark5B format in the mode where we offer 16 output 
channels, each with 32 MHz bandwidth.  Whenever Mark5B format is used, the 
"BITSTREAMS" block should be used in the vex2 file and whenever VDIF 
format is used, the "DATASTREAMS" block should be used (as is the case in 
the "tr040g" samples I previously sent you.

A couple notes (beyond those noted in the previous email):

1. There could be cases where some antennas use Mark5B/Bitstreams and 
others use VDIF/DATASTREAMS, but an antenna should never change between 
one and the other in one .vex file.

2. In the EXTENSIONS section, I have listed three "synth" values for the 
VLBA.  These refer to three frequency synthesizers in the antenna.  There 
may be more of these in the future.  The values for "synth1" and "synth2" 
are the same as two values currently (vex 1.5) stored in the comments in 
the IF block:

def DualFreqRPolTone/1;
* mode =  1    stations =Mk:Pt
      if_def = &IF_A : A : R :  2900.00 MHz : L : 1 MHz ; *    7900.00   2900.00  13cm     0 NA
      if_def = &IF_B : B : R :  7900.00 MHz : U : 1 MHz ; *    7900.00   2900.00  4cm     0 NA
enddef;

In this case, the 7900 (after the *) is the value for synth1 and 2900 (the 
secon value after the *) is the value for synth2.  When relevant, the
"synth3" tuning value is specified as the fourth value in the comment.
In this case the value is "0", meaning "not relevant, so no need to 
propoaget this in the EXTENSIONS block.

3. The .vex2 files are being crafted by hand.  It is possible there are 
errors in them.  So if something looks out of the ordinary, don't hesitate 
to ask me about it!


In both this case and for TR040G, there is a single mode in use during the 
observation.  I'll work to produce some examples involving more 
complicated setups.