[evlatests] Another useful EVLA frequency tool

[Walter Brisken]

I realized that it is often useful to know what sky frequency results from 
different variants of LO tunings and band selection even if the antenna is 
not tuned at the moment so I made calcfreq to do this.  It is compiled 
for Linux:

/home/parallax/evla/mibtalk/calcfreq

Running it with no parameters will give some vague instructions.

The easiest way to use it is to pass the band letter code and it will 
print values for the standard frequency:

parallax<160>% /home/parallax/evla/mibtalk/calcfreq L

IF 1 : L band
   L1 = 12928.000000  L2 = 14368.100000  SSLO = 607.900000
   1 GHz band : 607.900000 .. 1631.900000
   VLA band : 1439.900000 .. 1489.900000
   Signal 'L301-1' at 12928.000000 MHz -> 12320.100000 MHz (aliased to 32.100000 MHz)
   Signal 'L302-1' at 14368.100000 MHz -> 13760.200000 MHz (aliased to 575.800000 MHz)
   Signal 'L302-2' at 14447.900000 MHz -> 13840.000000 MHz (aliased to 496.000000 MHz)
   Signal 'T304' at 4096.000000 MHz -> 3488.100000 MHz (aliased to 607.900000 MHz)
   Signal '1024' at 1024.000000 MHz -> 416.100000 MHz (aliased to 416.100000 MHz)
   Signal '512' at 512.000000 MHz -> -95.900000 MHz (aliased to 95.900000 MHz)

IF 2 : L band
   L1 = 12928.000000  L2 = 14447.900000  SSLO = 528.100000
   1 GHz band : 528.100000 .. 1552.100000
   VLA band : 1360.100000 .. 1410.100000
   Signal 'L301-1' at 12928.000000 MHz -> 12399.900000 MHz (aliased to 111.900000 MHz)
   Signal 'L302-1' at 14368.100000 MHz -> 13840.000000 MHz (aliased to 496.000000 MHz)
   Signal 'L302-2' at 14447.900000 MHz -> 13919.800000 MHz (aliased to 416.200000 MHz)
   Signal 'T304' at 4096.000000 MHz -> 3567.900000 MHz (aliased to 528.100000 MHz)
   Signal '1024' at 1024.000000 MHz -> 495.900000 MHz (aliased to 495.900000 MHz)
   Signal '512' at 512.000000 MHz -> -16.100000 MHz (aliased to 16.100000 MHz)


This gives:
  * the first and second LO frequencies (L1 and L2)
  * the SSLO including T304, 4/P converter, and effective mixing at sampling
  * the sky frequencies digitized by the EVLA sampler
  * the VLA band that is reconstituted
  * a series of frequencies within the 1 GHz EVLA sampled band that various
    LO signals will appear -- hopefully useful in identifying mysterious lines
    in the spectra.

You can also specify explicit LO tunings, for example:

parallax<161>% /home/parallax/evla/mibtalk/calcfreq L 12928 14500

IF 1 : L band
   L1 = 12928.000000  L2 = 14500.000000  SSLO = 476.000000
   1 GHz band : 476.000000 .. 1500.000000
   VLA band : 1308.000000 .. 1358.000000
   Signal 'L301-1' at 12928.000000 MHz -> 12452.000000 MHz (aliased to 164.000000 MHz)
   Signal 'L302-1' at 14500.000000 MHz -> 14024.000000 MHz (aliased to 312.000000 MHz)
   Signal 'T304' at 4096.000000 MHz -> 3620.000000 MHz (aliased to 476.000000 MHz)
   Signal '1024' at 1024.000000 MHz -> 548.000000 MHz (aliased to 548.000000 MHz)
   Signal '512' at 512.000000 MHz -> 36.000000 MHz (aliased to 36.000000 MHz)

Illegal tunings will produce warnings.  Other command line parameters are 
allowed -- read the help info produced by running with no parameters.

Let me know if this is useful or have suggestions...

-Walter