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operations:documentation:lba_dbbc_config

Setting up the DBBC for LBA observations

There are two steps to setting up the DBBC - the first is the working out which IFs are needed and then setting the channels appropriately. The setups below list the most common setups and how to get them working. Specific examples from previous experiments are shown where possible. These should work for 16 MHz bandwidth observations with either 4 or 8 channels. Anything different from this needs much more work…

In general though, DRUDG should have calculated the IF frequencies correctly. You can check by comparing the with the frequencies on the LBA wiki and using LOs of 1900 MHz for S-band and 8600 MHz for X-band.

See these notes on how signals are routed through a DBBC for some background info before reading further.

X-band, single polarisation

As an example, here's how V252ai has it's frequencies set up according to the LBA wiki:

V252ai frequency setup

Running drudg on the VEX file produces the following IF setup for Ke:

define  ifd01         00000000000x            
ifa=1,agc,1
ifb=4,agc,1
lo=
lo=loa,7600.00,usb,rcp,off
lo=lob,7600.00,usb,rcp,off
enddef

As the notes on how signals are routed through a DBBC describe, we only need one CoMo as there's a common input IF and all frequencies are in the band of Filter 1 (512 - 1024 MHz). So we can drop ifb and lo=lob…. The input IF is X-band RCP which in input 1 and we want automatic gain control. The input power level for Ke in CoMo A should be 38000. So ifd01 should be edited to look like this:

define  ifd01         13073035822x
ifa=1,agc,1,38000
lo=
lo=loa,7600.00,usb,rcp,off
enddef

Drudg produced a dbbc01d procedure that looked like this:

define  dbbc01d       00000000000x            
bbc02=809.00,a,16.00
bbc04=825.00,a,16.00
bbc06=841.00,b,16.00
bbc08=857.00,b,16.00
enddef

The LO frequencies are correct but we want to use BBCs 01 to 04 and CoMo A. So the revised version looks like this:

define  dbbc01d       13073035822x
bbc01=809.00,a,16.00
bbc02=825.00,a,16.00
bbc03=841.00,a,16.00
bbc04=857.00,a,16.00
enddef

Lastly, in setup01 the mark5 mode needs checking. We start with

mk5b_mode=ext,0x0000CCCC,0

However, we want to pass through all bits from the first 4 BBCs, so it needs to be changed to this:

mk5b_mode=ext,0x000000ff,1

X-band, dual polarisation

As an example, here's how V465b has it's frequencies set up according to the LBA wiki:

V465b frequency setup

Running drudg on the VEX file produces the following IF setup for Ke (note you may get some warning messages, just persist and produce the files anyway):

define  ifd01         00000000000x            
ifa=1,agc,1
ifb=4,agc,1
lo=
lo=loa,7600.00,usb,rcp,off
lo=lob,7600.00,usb,rcp,off
enddef

As the notes on how signals are routed through a DBBC describe, we need two CoMos, one for X RCP and one for X LCP. The first four BBCs will need to be one polarisation (RCP) and the second four (from CoMo B) LCP. A note to the correlator and whoever is running fringe checks should be sent. The input IF for CoMo A is X-band RCP which in input 1, and for CoMo B X LCP is on input 1, and we want automatic gain control. The input power level for Ke in CoMos A and B should be 38000 and 33000 respectively. Lastly, we might as well make the lo settings correct (although they don't actually do anything to the DBBC). So ifd01 should be edited to look like this:

define  ifd01         13075124605x            
ifa=1,agc,1,38000
ifb=1,agc,1,33000
lo=
lo=loa,7600.00,usb,rcp,off
lo=lob,7600.00,usb,lcp,off
enddef

Drudg produced a dbbc01d procedure that looked like this:

define  dbbc01d       00000000000x            
bbc02=793.00,a,16.00
bbc04=809.00,a,16.00
bbc06=825.00,b,16.00
bbc08=841.00,b,16.00
bbc01=793.00,a,16.00
bbc03=809.00,a,16.00
bbc05=825.00,b,16.00
bbc07=841.00,b,16.00
enddef

The LO frequencies are correct but we want to use BBCs 01 to 04 and CoMo A for the RCP frequencies and BBCs 05 to 07 and CoMo B for LCP. So the revised version looks like this:

define  dbbc01d       13075124605x            
bbc01=793.00,a,16.00
bbc02=809.00,a,16.00
bbc03=825.00,a,16.00
bbc04=841.00,a,16.00
bbc05=793.00,b,16.00
bbc06=809.00,b,16.00
bbc07=825.00,b,16.00
bbc08=841.00,b,16.00
enddef

Lastly, in setup01 the mark5 mode needs checking. We start with

mk5b_mode=ext,0x0000FFFF,1

This is correct in this case as we haven't changed which BBCs we're passing through, just their frequency and polarisation assignments.

S-band, single polarisation

The setup here is essentially the same as for X-band single polarisation except the IF inputs and LO frequencies will differ.

S-band, dual polarisation

In this case the IF inputs setup dictates that you will have S-band LCP through CoMo A input 4, and S-band RCP through CoMo C, input 2. Consequently, ifd01 will need to look like this (for Ke):

define  ifd01         13075124605x            
ifa=4,agc,2,38000
ifc=2,agc,2,36000
lo=
lo=loa,1900.00,usb,lcp,off
lo=lob,1900.00,usb,rcp,off
enddef

As BBCs 1 - 4 are assigned to CoMo A, 5 - 8 to B, 9 - 12 to C and 13 - 16 to D, you want to set up BBCs 01 - 04 for LCP and 09 - 12 for RCP. e.g.

define  dbbc01d       13075124605x            
bbc01=300.00,a,16.00
bbc02=316.00,a,16.00
bbc03=332.00,a,16.00
bbc04=348.00,a,16.00
bbc09=300.00,c,16.00
bbc10=316.00,c,16.00
bbc11=332.00,c,16.00
bbc12=348.00,c,16.00
enddef

The Mark5 mode needs to pass though BBCs 1-4 and 9 - 12, so it should look like this:

mk5b_mode=ext,0x0FF000FF,1

Note for a 4-channel observation you would only need to set BBCs 1,2,9 and 10 and the Mark5 mode would be

mk5b_mode=ext,0x00F0000F,1

S/X-band, single polarisation

This setup is not dissimilar from S-band dual polarisation above, except CoMo A would be used for X-band.

Here's an example of a S-RCP and X-RCP setup:

define  ifd01         13075124605x            
ifa=1,agc,1,38000
ifc=2,agc,2,36000
lo=
lo=loa,7600.00,usb,rcp,off
lo=lob,1900.00,usb,rcp,off
enddef

As BBCs 1 - 4 are assigned to CoMo A, 5 - 8 to B, 9 - 12 to C and 13 - 16 to D, you want to set up BBCs 01 - 04 for X RCP and 09 - 12 for S RCP. e.g.

define  dbbc01d       13075124605x            
bbc01=793.00,a,16.00
bbc02=809.00,a,16.00
bbc03=825.00,a,16.00
bbc04=841.00,a,16.00
bbc09=300.00,c,16.00
bbc10=316.00,c,16.00
bbc11=332.00,c,16.00
bbc12=348.00,c,16.00
enddef

The Mark5 mode needs to pass though BBCs 1-4 and 9 - 12, so it should look like this:

mk5b_mode=ext,0x0FF000FF,1
/home/www/auscope/opswiki/data/pages/operations/documentation/lba_dbbc_config.txt · Last modified: 2013/03/28 05:35 by Jim Lovell