- First, power cycle the DBBC electronics, via the green switch (marked “EL”) on the rear panel of the DBBC.
- Check that the DBBC configuration file (C:\DBBC_CONF\dbbc_config_file.txt) is correct for the experiment you are setting up for. There is no obvious way to change which config file is loaded by DBBC_control so manual editing of this file is necessary. The format is as follows.
1 dbbc2.bit 612.99 4
1 dbbc2.bit 652.99 4
1 dbbc2.bit 752.99 4
1 dbbc2.bit 912.99 4
1 dbbc2.bit 632.89 4
1 dbbc2.bit 752.89 4
1 dbbc2.bit 812.89 4
1 dbbc2.bit 832.89 4
1 dbbc2.bit 325.99 4
1 dbbc2.bit 345.99 4
1 dbbc2.bit 365.99 4
1 dbbc2.bit 395.99 4
1 dbbc2.bit 445.99 4
1 dbbc2.bit 465.99 4
1 dbbc2.bit 319.99 4
1 dbbc2.bit 319.99 4
The 1 at the start says to use the core at the relevant address (1–16), the second line is the Xilinx config file to use (again, there is only one of these available and it is not user-configurable).
The third number is the frequency of the band edge for that module. If the upper band is selected for recording, then the number is the lower band edge. The planned connection for IVS observations is to use RCP only, with X-band into modules A and B, with S-band in C & D. This replicates the Ho setup with VCs 1–8 at X-band and 9–14 at S-band. The file shown is an adaptation of an R1 experiment (R1415 I think). The frequencies for X-band have been increased by 480 MHz (relative to Hobart’s VC frequencies) which S-band has been increased by 120 MHz. Cores 15 and 16 have “dummy” values as they are not used at Hobart.
The last number is the bandwidth of the recorded channel.
- Start “DBBC Control” from the desktop and answer “y” to reconfigure the DBBC. This takes ~2 minutes.
- Check that the green LEDs on the front of the DBBC are pulsing on a 1 PPS cycle. There should be two LEDs in each column that are pulsing in sync. The other LEDs in each column should also match. If they don’t, check the 10 MHz and PPS connections into the DBBC. In particular, make sure the Rohde and Schwarz oscillator is powered on as it is passing its 10 MHz reference signal through to the DBBC. It is needed as the current 10 MHz reference is “dirty” with a lot of unwanted harmonics. While the Rohde and Schwarz can handle this, it causes the DBBC to fall over. While you are there, check that the VSI cable from the back of the DBBC is securely plugged into the Mark5B slot (near the far right of the Mark5B). It is not particularly stable and if people have been working in the racks, it’s very likely to be bumped out of alignment.
- In the DBBC control window, you’ll need to enter a series of commands to turn off the AGC and to select the correct filter for each module. The command for this is
Which reports the current setup. Note that the commands into DBBC Control are very laggy - it will take up to 1 second for the commnd to be recognised. When you change settings and then check that it has worked, allow at least 2 seconds between the commands.
The output of the
dbbcifa command should be of the form
dbbcifa/1,36,agc,1,35347 where the first number is the filter (where 1 = 512–1024 MHz, 2 = 0–512 MHz, 3=1024–1536 MHz (Currently N/A) and 4 = 1536–2048 MHz (also N/A)), the second number (36 in this example) is the current attenuator setting (which ranges between 0 and 63 where 0 is +16 dB and 63 is −16 dB. If the reading is > 50 or < 10, consider changing the settings on the IF unit first.),
agc indicates that the active gain control is enabled, the fourth number is also the filter (Maybe…), and the fifth is the current 1s averaged total power for the filter. This last value should be . You need to turn off the AGC and replace it with a single value. If the reported value was acceptable, then use in the following command
Wait 2 seconds and then check the levels with
dbbcifa again. The 16 bit power level should be ~32000 ±8000. If this is ok, then repeat the procedure for
dbbcifb, replacing the attenuator setting with the appropriate level but still using filter 1.
dbbcifd, these are the S-band channels and should use filter two. The initial reading will use filter 1 and report gains set to 0 and power levels at zero. Set the band correctly using
dbbcifd=2,32,2. Wait 2 seconds and then check that the power levels are acceptable. If not, adjust the settings and/or the IF attenuator levels.
- Set the track formatting to GEOdesy mode with
This should conclude the set up for the DBBC. Next is the Mark5B which is mercifully simpler and less prone to mysterious faults.
- With the Mark5B running Debian Etch, no windows manager is started by default. If you want this, log in as oper and then use the command
startx. Start two xterms on the mark5B (or use Ctrl-Alt-F1, Ctrl-Alt-F2 to switch between terminal inputs if there is no windows manager). In one terminal, start the Mark5B software with
dimino -m0 &
In the second, run
tstdimino OR use the field system to send the following commands. Into the
tstdimino/fs, send the commands
Then check the synchronisation has worked with
This last command will return a string which should have the correct date and time, with syncerr_eq_0 and FHG_off. Next, set the mode on the recorder and then you can start the recording.
:1 at the end of the line indicates how the data should be reduced. The default recording mode is 16 channels, at 16 MHz (32 Ms/s), and 2 bits per sample for a 1024 Mbps data rate. For IVS experiments recording 16 channels, the reduction value should be set to 16/bw (i.e, for an experiment using a 4 MHz bandwidth, the mode should be set to
At this point, you are set to record with the
record=on. The fs equivalents of these
tstdimino commands should be something like
mk5=clock_set=32:ext going from Hobart.
For IVS schedules using the 12m, there is no support for the Mark5B recorder in fs 9.9.2. When this is upgraded to 9.10, less kludging should be necessary. For now, the skd file is drudg’d with the rack set to
none and the recorder as
Mark5A. The procedure file is then loaded into the field system and edited (using
pfmed from another terminal). The procedures to edit are
setupsx (or its equivalent),
setupsx, edit the section to read
Some of these entries are probably superfluous or incorrect (especially
preob should be edited to read
systemp should read
This last procedure is a link to a kludged bash script to make an estimate of the system temperature using the noise cal and 0.5 dB attenuators of the RF box together with some of the unused samplers in rack 1. The measured Tsys values are currently injected into the log as comments but a better solution would be to write an ANTAB file during the experiment.