The EVN correlator has 32 correlator boards, each of which can currently
handle a total of 4096 lags. The number of frequency points you will see
is half the number of lags used in the correlation, so there is a total number
of 65536 frequency points (
This capacity must be
divided among all the individual baseline/subband/polarization interferometers
that belong to your experiment. The relevant formula is:
You can use eq.(4) to find
the maximum number of frequency points
you can get per baseline/subband/polarization product. However, due to the
specifics of how the correlator is configured, there are some factors to
keep in mind:
Table 1 summarizes some valid configurations that use the
- can only be a power of 2.
- Minimum value is 16.
- Maximum value is 2048 (a baseline/subband/polarization product
must fit onto a single correlator board).
- can only be 1, 2, or 4 (of course, can be
2 or 4 only if you scheduled a dual-pol experiment).
- The product of and
must be .
must be a multiple of 4, such that
, your actual number of stations (hence its different
font in eq.(4) to draw attention to this subtlety).
, then we have to correlate your experiment
in multiple passes. If
(3 passes required),
to use in eq.(4).
- Note that if all other parameters are powers of 2,
then networks from 9-16 stations will all have the same maximum .
Thus, for example, dropping from
would gain you a factor
of 4 in maximum , all other parameters remaining constant.
that use the whole correlator.
||(Max. for 16 stations)
||(Max. for 8 stations; also current max. possible )
||(with only 4 stations, you can get more SB/Pol)
||(opposite extremes: many SB/Pol with low )