Links:
The
spectra from m5spec.py (.png)
t007
spectra/histograms (idl routines) (.ps) (
.pdf)
20
headers from t007_aa (.txt)
Other links:
using
the 12m,fs,rdbe at AO: an overview
Setup:
On 22oct21 data was taken with the
12meter, field system, rdbe backend, and mark6 recorder. This
test emulated the global vlbi xband mode 8x64 using bands
8240,8304,8368,8432 MHz
The setup was:
- 12meter tracking blank sky. The az, el was around -135, 30
deg so the telescope was looking back towards the control
room..
- xband receiver used:
- udc set to center 8336 MHz at 1500MHz (the
center of the 1-2 GHz IF). It is an upper side band (not
flipped)
- the 1500 MHz was converted to 750MHz with a hi side lo
(so the 750 band is flipped).
- 8336 is centered at 750MHz. This is sent to the rdbe's.
- The rdbe was set to:
- use 2 rdbes: RDBE2 & RDBE4, ddc mode.
- 8 channels each 64 MHz bw
- freqbands: 8240 (pola,b),8304 (a,b),8368 (a,b) and 8432
(a,b)
- these bands covered IF freq: 768 (8240) to 640
(8496Mhz).
- The 2 bit samples were then sent to the mark6 recorder
in vdif format.
- A tone at 8457 MHz was transmitted from the control room
back to the 12 meter telescope.
- The signal was seen in the if/lo using the spectrum
analyzer prior to being sent to the rdbe
The observing sequence consisted of:
- t007aa 30 second run
- offline:
- run sched on the t007.key file
- cp t007.vex files to vlbis1 (online)
- online
- run vex2snap to create the .snp file (we used
Flexbuf:mk6)
- start field system
- schedule= start running the schedule
- adjust the power levels in if/lo, a/d in rdbe and then
digitizer quantization.
- let rdbe take data for 30 seconds.
Files used for the experiment:
Taking the data
- start the field system (on vlbis1)
- fs
- schedule=t007aa
- # wait for rdbe to initialize
- # set the attenuator for the a/d (outside of field
system)
- # set the quantization levels.. cd /usr2/oper/bin
- ddc_quantize_read_adj_set.py
- adjust a/d levels:
- rdbe2
- Response: result =
!dbe_rms=0:20.870:20.305:-0.296:-0.611:127:65;
- rdbe4
- Response: result =
!dbe_rms=0:21.095:20.809:-0.481:-1.249:78:81;
- quantize results:
- !dbe_ddc_quantize?0:0:20500102:43456034:43613554:20430309:519:-518:0;
- !dbe_ddc_quantize?0:1:20482828:43547122:43524671:20445378:565:-564:1;
- !dbe_ddc_quantize?0:2:20468018:43548915:43522955:20460111:589:-590:0;
- !dbe_ddc_quantize?0:3:20447171:43500490:43669664:20382674:472:-473:-1;
- !dbe_ddc_quantize?0:0:20505002:43498081:43560229:20436687:478:-478:0;
- !dbe_ddc_quantize?0:1:20494170:43521106:43508327:20476396:559:-560:0;
- !dbe_ddc_quantize?0:2:20480624:43553534:43517212:20448629:552:-553:0;
- !dbe_ddc_quantize?0:3:20528731:43481228:43538824:20451216:485:-485:
- Then 30 secs of data was taken tracking blank sky.
Looking at the data
- logged on as oper@mk6 to get the data.
- The raw files were combined with vsb_fs. the combined file
was:
- ~oper/data/tmp/t007_aa_no0001/t007_aa_no0001
- The combined (but not vmuxed) files were copied to
gpuserv0:/media/DATA0/phildata/vlbi/211022/ and then
processed using some idl routines i've written (to input,
demux, and print the headers)l
- I also ran vmux, m5spec.py to verify that i got the same
results at the idl routines.
- vmux t007_aa_no0001/t007_aa_no0001 5032 6400
0,1,2,3,4,5,6,7 t007_aa_no0001.vmux
- arguments:
- samples/frame= 5000bytes*(8bits/2bits) = 20000
- sec/frame=1/128MHz * 20000 =.00015625 seconds
- frames/sec=1/.00015625625=6400 frames/sec/chan
- m5spec.py t007_aa_no0001.vmux VDIF_40000_2048_8_2 1000
16384
- arguments
- 40000 bytes data/frame. since we put 8 5000 byte
frames in 1 frame
- 2048Mps 128MsmpSec*2bits*8chan
- 1000: integrate for 1000 millisecs
- 16384 to a 16K xform -> 976.6 hz channel
resolution.
Print the headers from the combined (but not vmuxed file)
The voltage distribution and the spectra.
The spectra from
m5spec.py (.png)
Idl processing/plotting of spectra/voltages:
- 16384 frames of voltage data were input and demultiplexed
into the 8 channels (2 pols)*(4 freq bands)
- This was done twice for each experiment:
- using output thresholds of :
[-3.3349,-1,+1,3.3340] to compute the spectra
- using output thresholds of :
[0,1,2,3] when making the histograms
The plots show the spectra and voltage histograms for the
run:
- t007
spectra/histograms (.ps) (.pdf)
- This used netside=u,u in the .key file
- page 1-2: spectra
- Each frame is polA (black) polB (red) for a frequency
band
- rdbe2 has polA, rdbe4 is polB
- the setup parameters are listed
- The tone (at 8457 MHz) is showing up at + 25MHz
in the 8432 MHz band
- Page 2: voltage histograms:
- The 16384 frames (using lut values [0,1,2,3] for min
to max values were used to make a histogram
- Black is polA, red is polB, blue is the histogram from
the rdbe_quantize command query.
- the histograms have been normalized to the average
counts in channels 1,2
- Each frame is a different frequency band
- The ratio of the levels is about .46 ..
- it is the same for the quantize histogram as well as
the recorded data.
- The recorded voltage rms was computed: 1sigma
was about .942 digitizer levels. This is correct
for integer values.
Summary
- 8 frequency bands of 64 Mhz using the vlbi global setup
were output.
- We saw the 8457MHz tone 25 MHz from the edge of the
8432 Mhz band
- The quantize routine that is being used to set the
quantize levels is doing it correctly.
processing:x101/211022/fstest.pro
