1. Introduction

This document covers DBBC3 support in FS 10.0.0. This support does not provide the complete command set and functionality usually provided by the FS for a rack. However, it is sufficient for normal FS for VGOS observations if the schedule procedure library is provided by a specially crafted .skd schedule file (see the broad band support item of the drudg changes relative to the main branch sub-section of the Changes from FS9 document for more details).

2. FS DBBC3 support features

The following table gives the IFs and BBCs available based on the number of BBCs per IF and the number of IFs.

Table 1. DBBC3 IF lettering and BBC numbering
BBCs/IF IFs

1

2

3

4

5

6

7

8

A

B

C

D

E

F

G

H

8

1-8

9-16

17-24

25-32

33-40

41-48

49-56

57-64

12

1-8

9-16

17-24

25-32

33-40

41-48

49-56

57-64

65-68

73-76

81-84

89-92

97-100

105-109

113-116

121-124

16

1-8

9-16

17-24

25-32

33-40

41-48

49-56

57-64

65-72

73-80

81-88

89-96

97-104

105-112

113-120

121-128

2.1. FS DBBC3 channel labels

FS DBBC3 channels labels are constructed as nnns, where:

  • nnn is the BBC number 000-128

  • s is the side-band, l, u, etc.

For example, 032u is BBC 32, upper side-band.

2.2. Polarization designations

Polarizations used in .rxg files and the LO command are lcp or rcp (in onoff output l or r) regardless of the actual polarization pair in use. The pairs are: H and V; L and R; and X and Y. This will be fixed eventually (see #42). For now, since there are are at most two polarizations per receiver, the designations follow the alphabetical (in English) rule. This is, what matters is the alphabetical order of the first letter of the names in a polarization pair. The correction interpretation is determined by context. Thus:

  • l (or lcp) can represent horizontal linear polarization (“h”), LCP (“l”), or “x”

  • r (or rcp) can represent vertical linear polarization (“v”) , RCP (“r”), or “y”

2.3. Low level dbbc3 command

Direct low-level device communication is available with the dbbc3 command. Multi-line responses are supported, please use help=dbbc3 for more information.

2.4. BBC bbcNNN commands

Commands are provided for command and monitoring of individual BBCs. The commands have the form bbcNNN, where NNN runs 001 to 128. Please use help=bbcnnn for more information. Only a subset of these commands may be available depending on the DBBC3 configuration. See the table in the FS DBBC3 support features section above for the BBCs available per configuration.

2.5. IF conditioning module ifX command

Commands are provided for command and monitoring of individual IF conditioning modules. The commands are of the form ifX, where X runs from a to h. Please use help=ifx for more information. Only a subset of these commands may be available depending on the DBBC3 configuration. See the table in the FS DBBC3 support features section above for the IFs available per configuration.

2.6. IF total power iftpX command

Commands are provided for monitoring of total power data for individual IF conditioning modules. The commands are of the form iftpX, where X runs from a to h. Please use help=iftpx for more information. Only a subset of these commands may be available depending on the DBBC3 configuration. See the table in the FS DBBC3 support features section above for the IFs available per configuration.

2.7. BBC gain control bbc_gain command

The bbc_gain command can be used to control DBBC3 BBC gain control for individual or all BBCs. Please use help=bbc_gain for more information.

2.8. Continuous calibration control cont_cal command

The use of continuous calibration control, can be controlled and monitored using the cont_cal command. This includes whether continuous calibration is turned on and the polarity of the signal. Please use help=cont_cal for more information.

2.9. Tsys measurements

Tsys measurements are supported for both continuous and non-continuous calibration. The support is basically the same as it is for the DBBC2. DBBC3 BBCs can be selected individual or as evenl, evenu, oddl, and oddl. IFs can be selected individually. All detectors can be selected using all. The formbbc and formif selections are not supported yet.

Due to the heavy communication load required for this, measuring Tsys in schedules is not practical (it may be usable if the number of BBCs involved is very small). As a result, effective Tsys measurements for observations won’t be possible until there is support for multicast data.

2.10. Pointing and SEFD measurements

The fivept and onoff command support continuous and non-continuous calibration radiometer using individual DBBC3 detectors. For onff, the detectors can be selected as individually or as allbbc, all, allu, alll, or alli. The formbbc and formif selections are not supported yet.

Note
 See help=fivept and help=onoff for more information on using those commands.

2.11. Example procedure libraries

Temporary example DBBC3 station (dbbc3st.prc) and pointing (dbbc3po.prc) are available in st.default/proc.

2.12. New line in equip.ctl

The equip.ctl file has a new line at the end for the DBBC3. Its fields are:

  1. DBBC3 firmware version: v121 or greater

  2. BBCs per IF: 8, 12, or 16

  3. IFs: 1-8

You can see st.default/control/equip.ctl for an example.

2.13. Communication control program

Communication with DBBC3 is handled by the dbbcn control program. This implies that a DBBC3 can only be used simultaneously with a DBBC2 if it is accessed as the secondary DBBC2 with the dbbc2 and fila10g2 commands and fmset for time setting.