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Remote VLBI Observing

Setup and instructions

See also LBA setup and operation page.

The observing is done from a vnc session running from pcfscd:0 (password is the usual one). It is sharing the main display of the pcfscd observing machine (currently in rack 5) which has replace the aging ceduna machine.

Recommended VLBI setup for Ceduna

Current usage of cables from UER:

  • L1 - has RCP signal from receiver.
  • L6 - has LCP signal from receiver.
  • L2 - is connected to receiver tone port.
  • L5 - has the cal control signal.
  • Line behind DSO - has 5 MHz from the maser.

    In November 2009, 3 new cables were added. These are labeled A, B and C. They replace L1, L6 and the maser cable above. Bev has put additional labels on 2 of the new cables, L1 and L6 so that these instructions still make sense. She knows to use the new cables.

Dual Polarization setup

  1. Signal from L1 goes to LHS 30 dB amplifier;
  2. LHS 30 dB amplifier connected to input of LHS splitter.
  3. One of the splitter outputs goes to the LHS dial attenuator;
    • Output of LHS dial attenuators connected to RF connector on LHS of frequency translator;
    • SML01 goes to the LHS LO connector of frequency translator;
  4. Other splitter output goes to the LHS programmable attenuator (doesn’t matt1er which end)
    • other end of LHS programmable attenuator is connected to RF IN connector on LHS of square law detector.
    • DC OUT on LHS of square law detector is connected to VFC #2 input

The setup for the other polarization is very similar

  1. Signal from L6 goes to RHS 30 dB amplifier;
  2. RHS 30 dB amplifier connected to input of RHS splitter.
  3. One of the splitter outputs goes to the RHS dial attenuator;
    • Output of RHS dial attenuators connected to RF connector on RHS of frequency translator;
    • SML02 goes to the RHS LO connector of frequency translator (it should have the same frequency setting as SMY01);
  4. Other splitter output goes to the RHS programmable attenuator (doesn’t matter which end)
    • other end of RHS programmable attenuator is connected to RF IN connector on RHS of square law detector.
    • DC OUT on RHS of square law detector is connected to VFC #3 input

Single Polarization setup

This is very similar to the dual polarization setup, the only differences are:

  1. Take the polarization to be observed after it has been through the 30 dB amplifier and put it in the input to a splitter (don’t use the ones used in the dual polarization setup, we will be using them, perhaps use one of the ones above the frequency translator). So if it is LCP we want to observer, then take the signal from the RHS 30 dB amplifier and put it into the input of a splitter.
  2. Take the two splitter outputs and put them into the inputs of the LHS and RHS splitters used in the dual polarization setup
  3. SML01 and SML002 (the two used for the frequency translator LOs) will be set to different values in this mode (not the same value as they usually are for dual polarization observing).

NOTE: All of the Ceduna oscillators can be controlled by running the oscillator_gui.sh script as oper on pcfscd (probably best to do this within the VNC session). Instructions on commands for oscillator_gui.sh are below. Don’t use the SMY02 connected to the tone port for the second LO signal. I would recommend checking the coherence while Bev is there, be sure to switch the output from this oscillator off when you are finished. Set the tone oscillator (SMY02) to produce a tone 5 MHz above the bottom edge of the band for the LHS of the DAS and set the level to about 10 dBm. Bev knows what to look for on the CRO and can tell you if the system is coherent.

oscillator_gui.sh

This program must be run with the Ceduna PCFS is running.

  • To run oscillator_gui.sh, use ./oscillator_gui.sh in an oper@pcfscd terminal. It will take ~5 seconds to poll the oscillators and then show their current status in the terminal window. If there are garbled or suspect readings, p-lease try refreshing then display first (by pressing r and then enter). An example of the GUI output is included below

Oscillator Control “GUI”

Index Name Frequency Level (dBm) Ref Osc Output
1 Agilent 11.400 GHz 16.000 EXT ON
2 SML01 508.000 MHz 7.000 EXT ON
3 SML02 508.000 MHz 7.000 EXT ON
5 SMY02 664.500 MHz OFF EXT OFF

Please select the oscillator which you want to adjust, using the index or full name. Press r to refresh the display or q to quit..

  • To set the frequency of an oscillator, first select it using either the corresponding Index or its full name. The script will then prompt you for a new frequency and power level. Note than you can turn an oscillator output on or off with by setting the level to on or off.
  • When you are finished it is best to quit out rather than leave it running. Note that the status is only updated when you enter r, or when one of the outputs is changed.

V255 Methanol parallax setup

This is a combination of the dual and single polarization setups and is required for the v255 (and other methanol maser experiment setups). It is a dual polarization experiment, but uses two SMLs like the single polarization setups.

  1. Set the agilent to 11.1 GHz (rather than the standard 11.4 for the 6.7 GHz receiver)
  2. Signal from L1 goes to LHS 30 dB amplifier;
  3. LHS 30 dB amplifier connected to input of LHS dial attenuators;
  4. Output of LHS dial attenuators connected to RF connector on LHS of frequency translator;
  5. SML01 goes to the LHS LO connectors of frequency translator;
  6. IF connector on LHS frequency translator does to LHS programmable attenuator (doesn’t matter which end)
  7. other end of LHS programmable attenuator is connected to RF IN connector on LHS of square law detector.
  8. DC OUT on LHS of square law detector is connected to VFC #2 input.
  9. Check that the DAS levels are in the acceptable range for LO settings of 468 MHz (7 dBm) and 810 MHz (7dBm). We spend more time in the 810 MHz setting, so centre that as best you can while still keeping the DAS levels in range for 468 MHz.

The setup for the other polarization is the same, except the signal comes from L6 and replace all occurrences of LHS with RHS, use SML02 (set to 810 MHz, 7 dBm) for the RHS frequency translator LO, and the square law detector DC OUT goes to VFC #3.

To automate frequency changes, you should add two procedures to the experiment’s prc file, and add calls to these procedues at appropriate times in the experiment’s snp file. Template procedures are on pcfscd in /usr2/proc. as bbc01d.prc and bbc02d.prc and cat be appended to the experiment file with the command cat /usr2/proc/bbc01d.prc >> /usr2/proc/v255xcd.prc.

Setting the levels

  1. With the DAS running and an appropriate profile loaded, make sure that there is no CLOCK error on the DAS (this happens when the Ceduna tick phase changes, which happens when the station clock is restarted). If there is a CLOCK error the DELAY pots on the DAS High-resolution samplers will need to be manually rotated to get the right setting.
  2. Adjust the dial attenuators until the level on both DAS channels is as close to the centre of the range as possible.
  3. Adjust the programmable attenuators so that the square law detector is within its operating range (marked on the dial meter).

Record the setup

For all sorts of reasons it is critically important that you accurately record the setup used for the experiment. This information should be put in two places :

  1. The telescope log information on the experiment wiki
  2. In the PCFS log as a comment.

The information which should be recorded as a minimum is:

  • The agilent/front-end LO frequency and level.
  • The SML/back-end LOs frequency and level.
  • The tone used to check coherence (and where it was observed - bandsplitter port, fine tuner port etc)
  • The DAS profile and the cable connecting the DAS to the vsib box (BG1/straight through or BG3/64 MHz etc).
  • The disk the data is being recorded to (make sure to also update the disk summary table).
  • The approximate clock offset (as reported by clkoff).
  • Which polarization is being sent to which DAS processor.

Timed commands on the PCFS

Its a good idea to make sure that certain information (clock offsets, system temperature, weather etc.) are monitored regularly throughout an experiment. For some experiments some, or all of these checks may be scheduled in (as part of a preob or midob procedure say). Either before the experiment, or soon after it has started look at what checks are being performed regularly by the schedule and add any which are not using a timed command.

  1. To check what is part of the schedule go to the directory /usr2/proc on ceduna and look in the .prc file for the experiment (e.g. for the experiment v275c this would be the file /usr2/proc/v275ccd.prc). Look at the procedures preob, midob and postob (if they are defined) and see what commands are being issued. These commands will be executed once per scan and so if the experiment has short scans (a few-10 minutes), then you don’t need to worry about those commands.
  2. For commands not in the pre/mid/post ob procedures, or for experiments with long (> 15 minute) scans, you can set the pcfs to issue timed commands using
    clkoff@!,15m
    This will execute clkoff now and every 15 minutes into the future (when you change schedules many of the timed commands get canceled). To see which timed commands are in the system
    ti
    If you want to cancel a timed command
    clkoff@

Computer Setup:

The following process should be running in the cdvsi vnc session during a VLBI session :

  • PCFS (pcfscd)
  • PCFS monitor (pcfscd)
  • STALM (pcfscd) - haven’t got this working at present. A workaround is to use the pmSTALM.sh script. Details of this script can be found at pmSTALM
  • DAS (pcfscd)
  • cdisko2.pl (pcfscd)

This is also the appropriate place to run bruce calibration observations or change oscillator frequencies/test coherence with oscillator_gui.sh

To start/restart the vnc session on pcfscd (if necessary)

  1. Login to pcfscd as oper
  2. Run x11vnc -bg -shared -alwaysshared -forever -usepw -display :0 if it is not currently running. Killing the x11vnc process should be safe for any current experiment, but this is not guaranteed.

The window manager is pretty primitive, but it works. To get an xterm left click in the background and select xterm from the menu.

To access the vnc session

  • On a Linux machine (e.g. newsmerd or cdvsi) vncviewer -shared pcfscd:0 (Usual password)
  • On a graphical VNC client (e.g. Chicken of the VNC on a Mac), just give the machine name as pcfscd.phys.utas.edu.au and the display as 0 . Make sure that you allow other users to also connect.

To run the PCFS

  1. As oper@pcfscd, first check that the NTP time is correct with ntpq -np. The Offset should be <10 (ms) to the server at 131.217.61.171. If it isn’t, you should check that the NTP server is working correctly (use vncviewer tac32cd and check the tac32 software hasn’t frozen up). Once the tac32 is confirmed as good, issue these commands as root to resynch to the NTP server
    /etc/init.d/ntp stop
    ntpdate tac32cd
    /etc/init.d/ntp start
    Then check the NTP status with ntpq -np
  2. To start the FS, run fs

To start the pcfs status monitor

From an xterm on pcfcd (as oper)
xterm -geometry 86×6 -e monit2 &

To run the DAS

  1. From an xterm on pcfscd (as oper)

das
# When the xdos window starts it will automatically run the DOS DAS program. When it starts, select vsop.pro as the profile initially (that has the right communications options). After the initial setup, then select the profile you want.

To run cdisko

From an xterm on pcfscd (as oper)
cdisko2.pl &
It’s a good idea to check that the NTP time on cdvsi is correct before starting any recordings. To do this, ssh to vlbi@cdvsi and run ntpq -np. The Offset shjould be <10 (ms). If it isn’t, you should check that the NTP server is working correctly (use vncviewer tac32cd and check the tac32 software hasn’t frozen up). Once the tac32 is confirmed as good, issue these commands as root to resynch to the NTP server
/etc/init.d/ntp stop
ntpdate tac32cd
/etc/init.d/ntp start
Then check the NTP status with ntpq -np

To change xraid disks

See the detailed instructions here. Although these refer to hovsi the instructions apply in exactly the same way to cdvsi. NOTE: If you are running in a vnc session you may have trouble running the Xraid Admin tools if the DISPLAY environment variable isn’t set correctly (try ssh -X root@cdvsi). If its causing problems its usually safe to skip this step. Record the 60 seconds of test data as suggested and if that works OK, the disks are likely to be fine. If not, ask for help from an expert.

To change oscillator frequencies etc

  1. From an xterm on pcfscd (as oper)
    oscillator_gui.sh

To check coherence (remotely without using Bev to view the CRO display):

There is a camera connected to 131.217.61.185 which should show you the cro.

To run bruce

  1. Start an xterm on ellis (as observer)

/obs/develop/sol/mapping/bruce -f 4 -r rakbus -s sam30m -a sys30m




================= Here there be obsolete documentation =================

The observing is done from a vnc session running from the vlbi account on cdvsi (password the pre-Dec 2009 vlbi@cdvsi account password). Its probably best to make it display 1 so that its easy for everyone to find. If not, let people know what it is, or you can always ps -ef | grep vnc on cdvsi to find it. If you are connecting to the remote VLBI observing VNC session, make sure your client is setup so that it allows others to also connect.

This is a work in progress. If you have additional suggestions or improvements, please edit the page and add them.

Recommended VLBI setup for Ceduna

Current usage of cables from UER:

  • L1 - has RCP signal from receiver.
  • L6 - has LCP signal from receiver.
  • L2 - is connected to receiver tone port.
  • L5 - has the cal control signal.
  • Line behind DSO - has 5 MHz from the maser.

    In November 2009, 3 new cables were added. These are labeled A, B and C. They replace L1, L6 and the maser cable above. Bev has put additional labels on 2 of the new cables, L1 and L6 so that these instructions still make sense. She knows to use the new cables.

Dual Polarization setup

  1. Signal from L1 goes to LHS 30 dB amplifier;
  2. LHS 30 dB amplifier connected to input of LHS splitter.
  3. One of the splitter outputs goes to the LHS dial attenuator;
    • Output of LHS dial attenuators connected to RF connector on LHS of frequency translator;
    • SMY01 (middle SMY?) goes to the LHS LO connector of frequency translator;
  4. Other splitter output goes to the LHS programmable attenuator (doesn’t matter which end)
    • other end of LHS programmable attenuator is connected to RF IN connector on LHS of square law detector.
    • DC OUT on LHS of square law detector is connected to VFC #2 input

The setup for the other polarization is very similar

  1. Signal from L6 goes to RHS 30 dB amplifier;
  2. RHS 30 dB amplifier connected to input of RHS splitter.
  3. One of the splitter outputs goes to the RHS dial attenuator;
    • Output of RHS dial attenuators connected to RF connector on RHS of frequency translator;
    • SMY03 goes to the RHS LO connector of frequency translator (it should have the same frequency setting as SMY01);
  4. Other splitter output goes to the RHS programmable attenuator (doesn’t matter which end)
    • other end of RHS programmable attenuator is connected to RF IN connector on RHS of square law detector.
    • DC OUT on RHS of square law detector is connected to VFC #3 input

Single Polarization setup

This is very similar to the dual polarization setup, the only differences are:

  1. Take the polarization to be observed after it has been through the 30 dB amplifier and put it in the input to a splitter (don’t use the ones used in the dual polarization setup, we will be using them, perhaps use one of the ones above the frequency translator). So if it is LCP we want to observer, then take the signal from the RHS 30 dB amplifier and put it into the input of a splitter.
  2. Take the two splitter outputs and put them into the inputs of the LHS and RHS splitters used in the dual polarization setup
  3. SMY01 and SMY03 (the two used for the frequency translator LOs) will be set to different values in this mode (not the same value as they usually are for dual polarization observing).

NOTE: All of the Ceduna oscillators can be controlled by running the rs.tcl script as oper on ceduna (probably best to do this within the cdvsi VNC session). Instructions on commands for rs.tcl are below. Don’t use the SMY02 connected to the tone port for the second LO signal. I would recommend checking the coherence while Bev is there, be sure to switch the output from this oscillator off when you are finished. Set the tone oscillator (SMY02) to produce a tone 5 MHz above the bottom edge of the band for the LHS of the DAS and set the level to about 10 dBm. Bev knows what to look for on the CRO and can tell you if the system is coherent.

rs.tcl commands

This program can be run with the Ceduna PCFS is running.

  • To run rs.tcl ssh -X oper@ceduna (or make sure you can remote display). Then rs.tcl. You might need to be patient it sometimes takes 30 seconds or more before it shows something. You should see a grey window with a list of oscillators and a User input line down the bottom.
  • To check the current frequency settings of a particular oscillator double click on its name in the window. The information from the SMYs is formatted nicely, but the output from the Agilent is a not quite so obvious, the first number is the frequency in Hz and the second the level in dBm.
  • To set the frequency of an oscillator, first select it (double click). Then type the command rf 637 mhz in the User input window (obviously replacing the frequency with what ever is appropriate).
  • To set the level of the selected oscillator type the command lev 7 dbm (again replacing the value with what ever is appropriate).
  • To switch the output of the oscillator off (e.g. for the tone oscillator when it is not in use) type the command lev off. You can switch it on again (to what ever the previous level was) with lev on.
  • When you are finished it is best to quit out rather than leaving it running.

V255 Methanol parallax setup

This is a combination of the dual and single polarization setups and is required for the v255 (and other methanol maser experiment setups). It is a dual polarization experiment, but uses two SMYs like the single polarization setups.

  1. Set the agilent to 11.1 GHz (rather than the standard 11.4 for the 6.7 GHz receiver)
  2. Signal from L1 goes to LHS 30 dB amplifier;
  3. LHS 30 dB amplifier connected to input of LHS dial attenuators;
  4. Output of LHS dial attenuators connected to RF connector on LHS of frequency translator;
  5. SMY01 (middle SMY?) goes to the LHS LO connectors of frequency translator;
  6. IF connector on LHS frequency translator does to LHS programmable attenuator (doesn’t matter which end)
  7. other end of LHS programmable attenuator is connected to RF IN connector on LHS of square law detector.
  8. DC OUT on LHS of square law detector is connected to VFC #2 input.
  9. Check that the DAS levels are in the acceptable range for LO settings of 468 MHz (7 dBm) and 810 MHz (7dBm). We spend more time in the 810 MHz setting, so centre that as best you can while still keeping the DAS levels in range for 468 MHz.

The setup for the other polarization is the same, except the signal comes from L6 and replace all occurrences of LHS with RHS, use the another SMY (set to 810 MHz, 7 dBm) for the RHS frequency translator LO, and the square law detector DC OUT goes to VFC #3.

NOTE: Don’t use the SMY connected to the tone port for the second LO signal. The SMY not used in the dual polarization setup (the bottom SMY?) is either not connected, or doesn’t work on the GPIB, so that will have to be set manually by Bev. It should be used for the RHS LO on the frequency translator as that is not changed during the experiment. I would recommend checking that that oscillator is working while Bev is present (do a coherence check), since we use it in-frequently and its possible it may be faulty.

Setting the levels

  1. With the DAS running and an appropriate profile loaded, make sure that there is no CLOCK error on the DAS (this happens when the Ceduna tick phase changes, which happens when the station clock is restarted). If there is a CLOCK error the DELAY pots on the DAS High-resolution samplers will need to be manually rotated to get the right setting.
  2. Adjust the dial attenuators until the level on both DAS channels is as close to the centre of the range as possible.
  3. Adjust the programmable attenuators so that the square law detector is within its operating range (marked on the dial meter).

Record the setup

For all sorts of reasons it is critically important that you accurately record the setup used for the experiment. This information should be put in two places :

  1. The telescope log information on the experiment wiki
  2. In the PCFS log as a comment.

The information which should be recorded as a minimum is:

  • The agilent/front-end LO frequency and level.
  • The SMY/back-end LO (or LOs) frequency and level.
  • The tone used to check coherence (and where it was observed - bandsplitter port, fine tuner port etc)
  • The DAS profile and the cable connecting the DAS to the vsib box (BG1/straight through or BG3/64 MHz etc).
  • The disk the data is being recorded to (make sure to also update the disk summary table).
  • The approximate clock offset (as reported by clkoff).
  • Which polarization is being sent to which DAS processor.

Timed commands on the PCFS

Its a good idea to make sure that certain information (clock offsets, system temperature, weather etc.) are monitored regularly throughout an experiment. For some experiments some, or all of these checks may be scheduled in (as part of a preob or midob procedure say). Either before the experiment, or soon after it has started look at what checks are being performed regularly by the schedule and add any which are not using a timed command.

  1. To check what is part of the schedule go to the directory /usr2/proc on ceduna and look in the .prc file for the experiment (e.g. for the experiment v275c this would be the file /usr2/proc/v275ccd.prc). Look at the procedures preob, midob and postob (if they are defined) and see what commands are being issued. These commands will be executed once per scan and so if the experiment has short scans (a few-10 minutes), then you don’t need to worry about those commands.
  2. For commands not in the pre/mid/post ob procedures, or for experiments with long (> 15 minute) scans, you can set the pcfs to issue timed commands using
    clkoff@!,15m
    This will execute clkoff now and every 15 minutes into the future (when you change schedules many of the timed commands get canceled). To see which timed commands are in the system
    ti
    If you want to cancel a timed command
    clkoff@

Computer Setup:

The following process should be running in the cdvsi vnc session during a VLBI session :

  • PCFS (ceduna)
  • PCFS monitor (ceduna)
  • STALM (ceduna) - haven’t got this working remotely at present, and since you can’t hear alarms sound in Ceduna when you aren’t there it probably doesn’t matter. A workaround is to use the pmSTALM.sh script. Details of this script can be found at pmSTALM
  • DAS (ceduna)
  • cdisko (sille)

This is also the appropriate place to run bruce calibration observations or change oscillator frequencies/test coherence with rs.tcl

To start the vnc session on cdvsi (if necessary)

  1. Login to cdvsi as vlbi
  2. vncserver -alwaysshared -geometry 1024×768 :1

The window manager is pretty primitive, but it works. To get an xterm left click in the background and select xterm from the menu.

To access the vnc session

  • On a Linux machine (e.g. newsmerd or cdvsi) vncviewer -shared cdvsi:1 You will need to enter the old (pre-Dec 2009) vlbi@cdvsi password to see it.
  • On a graphical VNC client (e.g. Chicken of the VNC on a Mac), just give the machine name as cdvsi.phys.utas.edu.au and the display as 1 (assuming that the vncserver has been started on display 1). Make sure that you allow other users to also connect.

To run the PCFS

  1. ssh -l oper ceduna
  2. fs

To start the pcfs status monitor

From an xterm on ceduna (as oper)
xterm -name monit2 -e /usr2/fs/bin/monit2 &

To run the DAS

  1. From an xterm on ceduna (as oper)

das
# When the xdos window starts it will automatically run the DOS DAS program. When it starts, select vsop.pro as the profile initially (that has the right communications options). After the initial setup, then select the profile you want.

To run cdisko

From an xterm on sille (as observer)
cdisko.pl
Its not a bad idea to make sure that the time on sille is correct prior to starting cdisko. To do this issue the command sudo ntpdate tac32cd (the password required is just the standard observer@sille password.

NOTE: There is currently a bug in cdisko (version 3.0c) where it has a memory leak. This can cause problems on Sille (which isn’t a powerful machine). It is strongly recommended that you quit the cdisko client once a day and restart it to avoid it freezing.

To change xraid disks

See the detailed instructions here. Although these refer to hovsi the instructions apply in exactly the same way to cdvsi. NOTE: If you are running in a vnc session you may have trouble running the Xraid Admin tools if the DISPLAY environment variable isn’t set correctly (try ssh -X root@cdvsi). If its causing problems its usually safe to skip this step. Record the 60 seconds of test data as suggested and if that works OK, the disks are likely to be fine. If not, ask for help from an expert.

To change oscillator frequencies etc

  1. From an xterm on ceduna (as oper)
    rs.tcl
    Take care to exit this nicely, as its easy to get the GPIB bus in a knot which requires rebooting Ceduna to fix

To check coherence (remotely without using Bev to view the CRO display):

There is a camera connected to 131.217.61.185 which should show you the cro.

The coherence checking assumes that:

  1. You have the IF monitor port outputs connected to programmable attenuators, then to the square law detectors and then to VFCs 2 & 3. This is the normal setup for system temperature measurement, as is described in the setup section above.
  2. SMY02 is set to produce a tone 500 Hz (not 5 MHz) above the lower-band edge for the current DAS profile setup.
  3. SMY02 is connected to the tone port on the receiver.
  4. From an xterm on ceduna (as oper) type the command coherence. Make sure that the system temperature isn’t being measure at the time, since only one user can access the VFCs at a time.

coherence is an alias which

  1. Switches the output of SMY02 on
  2. Collects 3 seconds worth of data from VFCs# 2 & 3, sampling at 4000 Hz
  3. Switches the output of SMY02 off (the tone is on for a total of about 5 seconds, so try and do this when the antenna is not collecting good data (e.g. during a slew).
  4. Runs an octave program which Fourier transforms the data and plots the amplitude of the FT against frequency. NOTE: The octave script is quite slow and to see the plots you need to have the display set properly (ssh -X oper@ceduna will usually do the trick). Once the first plot appears, hit return to see the second which zooms in on the region around 500 Hz and also shows the difference between the two channels. Once you’ve looked at this, hit return again (perhaps twice) and the plot should disappear (eventually).
  5. Should you ever want to look at it again the zoomed version of the plot is also saved to /usr2/log/coherence.XXXXX.YYY.ps where XXXXX is the modified Julian Day and .YYY is the decimal fraction of a day.

When we check coherence we inject a tone, sample the output from the IF monitor ports and then Fourier transform that to find the tone. Normally we take the output of the DAS bandsplitter or fine tuner ports compare them with 5 MHz from the maser on an oscilloscope, however, that isn’t possible for remote observation. Also, the signals from the bandsplitter and fine tuner ports are at baseband and go through the DAS’s automatic gain control system. This means that they aren’t good for system temperature measurements. The IF monitor port outputs (which we normally use for system temperature measurement) are centred at 96 MHz (whatever sky frequency is picked by the LO input into the frequency translator ends up at 96 MHz on the IF output). This means that if you are observing with VSOP profile with 8425 MHz centre frequency you have 2 x 16 MHz bands 8409–8425 MHz and 8425–8441 MHz (the first is output on the bandsplitter 0–16 MHz) and the second on the fine tuner (0–16 MHz). A tone at 8409.0005 Hz will appear 500 Hz above the lower band edge (i.e. at 80.0005 MHz on the IF monitor port). When we sample this broadband signal at 4000 Hz, we still see at tone at 500 Hz, due to aliasing in our massively undersampled system. Although it is significantly weaker than the signal you get if you use the output from the bandsplitter ports, the advantage is that when the tone is switched off (which is nearly all the time), you can use it for system temperature measurements. If you want to demonstrate that there is no tone at 500 Hz with when its switched off run the samtest.lnx and octave ~/prog/coherence.m programs by hand with the tone off (alias | grep coherence will show you the sequence of commands and their syntax which is use for the coherence checking process). One problem discovered in July 09 is that high SMY02 output levels (10+ dBm) will not show coherence with this process, at least for the 8.4 GHz receiver. Levels of 8 dBm are ok.

To run bruce

  1. Start an xterm on ellis (as observer)

/obs/develop/sol/mapping/bruce -f 4 -r rakbus -s sam30m -a sys30m

Notes on MAR10 LBA session:

  • Bev and Mark at telescope 9 March.
    • Checked coherence using standard (not computer controlled) method for the two v255i frequency setups.
    • SMY01 is connected to the LO port on the LHS of the frequency translator.
    • SMY01 can be controlled from within the PCFS using the command sy=/usr2/st/bin/freq_smy01 <freq>, where <freq> is the frequency in MHz. This allows you to change frequency from within a schedule by defining an appropriate procedure (see for example the bbc01d and bbc02d procedures in v255icd.prc and how they are called in v255icd.snp).
    • SML01 is connected to the LO port on the RHS of the frequency translator.
    • The DAS levels were set to be reasonable for both the 468 MHz and 810 MHz (ICRF & maser) setups for v255i. Because the schedule spends most of its time in the maser setup the levels for that are better centred. Even though the level is off the scale for the 468 MHz setup the stats reported by cdisko are OK and there were no obvious problems in the fringes during the fringe checks. The system temperature for the first channel is not reliable though as the level into the square law detectors isn’t optical for the first channel. Use the values from the second channel.
    • SMY02 is connected to the tone port and could potentially be used for remote coherence checks, although this probably isn’t worth worrying about unless a fringe check shows problems.
    • The 500 Hz reference tone is connected into VFC#4 and the output from the IF#1 bandsplitter is connected to VFC#5.
    • There were problems getting the pcfs to read the systemp procedure for v255i properly. The correct procedure had to be entered by hand using pfmed. The same problem also occurred for v316c.

Notes on JUL09 LBA session:

  • Bev and Mark at telescope 1 July.
    • Fixed GPIB problems (loose GPIB connector into the back of one of the SMYs).
    • Went through disk change procedures and use of BG3/64 MHz cable.
    • Tried various methods of being able to measure system temperature and check coherence remotely.
  • Bev and Mark at telescope 2 July.
    • Finalised cabling for system temperature and coherence check system, tested it worked.
    • Fringe check 22316 MHz, VSOP_HO profile. Fringes Hobart-Ceduna-Mopra
    • Installed BG3/64 MHz cable, 22316 MHz centre frequency and 64MHZ profile. No fringes, but problem appears to be with fringe-check correlator. 64 MHz bandpass from 22 GHz system is inverted (as it is at Hobart), unlike lower frequencies, this can’t be flipped/corrected in the DAS profile. Inserted tone into system and appeared at expected location in band (used fauto to look at this.
    • Did a couple of scans on Virgo and 1253–05. Sources detected, both are around 20 Jy at 22 GHz and were at moderately low elevations of around 20–30 degrees, but scans noisy. The weather at Ceduna was overcast and windy (Hobart was more overcast but still). Implied system temperatures from rough calculations very high, suspect true system temperature around 2500 Jy at Hobart and similar (perhaps 3500 Jy) at Ceduna. Cal heights used for system temperature measurements have been scaled to give roughly these values.
    • Changed frequency to 22235 MHz and observed Orion. Strongest maser emission seen clearly both Hobart and Ceduna in the same channel (i.e. demonstrating that both have the same inversion). At Hobart we were using 64MHZ_F.PRO (but you get the same results with 64MHZ_N.PRO)
    • Changed back to BG1/straight through cable and VSOP_HO.PRO. Fringes again, Bev and Mark left, running remotely.
    • Getting missing 1PPS errors at the rate of 1–2 per hour. According to Aidan that is typical for Ceduna.

Test of change to 22 GHz system 9 June 2009 (Simon & Bev/Mark)

  1. Simon checked that the correlator was working by making an observation of Mon R2 at 6.7 GHz with a 4 MHz bandwidth. Source detected strongly.
  2. Bev and Mark swapped from the 6.7 GHz receiver to 22 GHz, which required the following changes
    • Agilent set to 17.4 GHz, 14 dBm.
    • SMY01 set to 417 MHz, 11 dBm (this gives a sky centre frequency into the DAS of 22235 MHz).
    • programmable attenuators (into the square law detectors) set to 5 dB for both.
    • dial attenuators (into the DAS) set to 12 dB for both.
  3. Simon used the correlator to observe the Orion water masers with a 16 MHz bandwidth, these were detected strongly.
  4. Simon used bruce to make scans on Venus (detected easily) and 0537–441 (detected in most scans). The weather was overcast, with occasional heavy showers.
  5. We tried to check the coherence of the system by sending a tone from SMY01 up L6. We used 889.4 MHz (25th harmonic of 22235 MHz) and tried various levels, the SMY gave errors for levels higher than 13 dBm. We didn’t have much luck getting a tone, although it did work briefly (very strong signal). We suspected a bad cable, but changing BNC cables in the control room didn’t fix the problem. The connectors were all tight. I tried again after swapping back to 6.7 GHz, I still couldn’t see any tone in the correlator output.
  6. Bev and Mark then swapped back to 6.7 GHz, which required the following changes
    • Agilent set to 11.4 GHz, 14 dBm.
    • SMY01 set to 521 MHz, 11 dBm (this gives a sky centre frequency into the DAS of 6669 MHz).
    • programmable attenuators (into the square law detectors) set to 1 & 2 dB for left and right respectively.
    • dial attenuators (into the DAS) set to 5 dB for both.
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