Spectrometers

The Observatory maintains two spectrometer systems, filter banks and a digital Millimeter Autocorrelator (MAC). Table 3 lists the filter-bank spectrometers which are available, while Table 4 lists the instrumental parameters for the MAC. For the filter bank spectrometers, the multiplexer will provide two spectra with a total number of spectral channels not in excess of 512. Thus, it is always possible to record simultaneously the output of two filter banks. Except for the 30 kHz bank, all of the filter banks have two independent 128 channel sections. You can configure these banks in one of two ways. In the ``series'' option, the two sections are placed end to end in frequency space, , the 256 channels are sequential in frequency. In the ``parallel'' mode, the two sections are used independently to accept different receiver (polarization) channels. The series mode is appropriate for observations requiring a large bandwidth. The parallel mode is useful for narrow band observations in which two different frequency resolutions are needed.

Table 3: 12m Filter Spectrometer Characteristics

Filter Resolution	Channels per Bank	Filter Banks Available
2 MHz	256	2
1 MHz	256	2
500 kHz	256	1
250 kHz	256	1
100 kHz	256	1
30 kHz¹	128	1

¹ Series option only.

Table 4: Millimeter Autocorrelator (MAC) Configurations
Total Bandwidth Useable Bandwidth¹ Channels $\Delta\nu$ ² Spectral Resolution

(MHz) (MHz) (kHz) (kHz)

2 IF Modes

800 600^* 2048 390.6 781.2

800 600 4096 195.3 390.6

400 300^* 4096 97.6 195.3

400 300 8192 48.8 97.6

200 150^* 8192 24.4 48.8

200 150 16384 12.2 24.4

100 75^* 16384 6.1 12.2

100 75 32768 3.0 6.1

4 IF Modes

800 600^* 1024 781.2 1562.0

800 600 2048 390.6 781.2

400 300^* 2048 195.3 390.6

400 300 4096 97.6 195.3

200 150^* 4096 48.8 97.6

200 150 8192 24.4 48.8

100 75^* 8192 12.2 24.4

100 75 16384 6.1 12.2

8 IF Modes

800 600^* 512 1562.5 3125.0

800 600 1024 781.2 1562.0

400 300^* 1024 390.6 781.2

400 300 2048 195.3 390.6

200 150^* 2048 97.6 195.3

200 150 4096 48.8 97.6

100 75^* 4096 24.4 48.8

100 75 8192 12.2 24.4

¹  The useable bandwidth takes account of the 75% efficiency of the analog filters.

²  NOTE: This is the frequency sampling interval, not the FWHM channel width,

   for a given channel. The FWHM channel width is 2.0 times this value.

All values in this table refer to each IF.

Modes tagged with a * are produced by dropping the last half of the lags.

Total Bandwidth	Useable Bandwidth¹	Channels	$\Delta\nu$ ²	Spectral Resolution
(MHz)	(MHz)		(kHz)	(kHz)
2 IF Modes
800	600^*	2048	390.6	781.2
800	600	4096	195.3	390.6
400	300^*	4096	97.6	195.3
400	300	8192	48.8	97.6
200	150^*	8192	24.4	48.8
200	150	16384	12.2	24.4
100	75^*	16384	6.1	12.2
100	75	32768	3.0	6.1
4 IF Modes
800	600^*	1024	781.2	1562.0
800	600	2048	390.6	781.2
400	300^*	2048	195.3	390.6
400	300	4096	97.6	195.3
200	150^*	4096	48.8	97.6
200	150	8192	24.4	48.8
100	75^*	8192	12.2	24.4
100	75	16384	6.1	12.2
8 IF Modes
800	600^*	512	1562.5	3125.0
800	600	1024	781.2	1562.0
400	300^*	1024	390.6	781.2
400	300	2048	195.3	390.6
200	150^*	2048	97.6	195.3
200	150	4096	48.8	97.6
100	75^*	4096	24.4	48.8
100	75	8192	12.2	24.4
¹ The useable bandwidth takes account of the 75% efficiency of the analog filters.
² NOTE: This is the frequency sampling interval, not the FWHM channel width,
for a given channel. The FWHM channel width is 2.0 times this value.
All values in this table refer to each IF.
Modes tagged with a * are produced by dropping the last half of the lags.