Other links:
using the
12m,fs,rdbe at AO: an overview
Setup:
On 18oct21 data was taken with the
12meter, field system, rdbe backend, and mark6 recorder.
Previous tests only used rdbe2. This test used both rdbe2 and
rdbe4 using 8 channels.
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 8550 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).
- 8550 is centered at 750MHz. This is sent to the rdbe's.
- The rdbe was set to:
- use 2 rdbes: RDBE2 & RDBE4
- 8 channels each 16 MHz bw
- freqbands: 8532 (pola,b),8548 (a,b),8564 (a,b) and 8580
(a,b)
- these bands covered 768 (8532) to 704 (8596Mhz) and did
not cross a 128 Mhz boundary of the rdbe 4 pfb outputs.
- The 2 bit samples were then sent to the mark6 recorder
in vdif format.
- A tone at 8543 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
- tone seen at 1482 MHz in 1-2 ghz IF (unflipped)
- tone seen at 768 MHz in the 500-1000MHz IF (this band is
flipped in freq)
The observing sequence consisted of:
- t006aa 60 second run
- offline:
- run sched on the t006.key file
- cp t006.vex files to vlbis1 (online)
- online
- run vex2snap to create the .snp file
- 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 60 seconds.
Files used for the experiment:
Taking the data
- start the field system (on vlbis1)
- fs
- schedule=t006aa
- # 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=0:19.674:20.017:-0.399:-0.332:127:71;
- rdbe4
- Response: result =
!dbe_rms=0:20.184:19.890:-0.457:-1.060:83:77;
- quantize results:
- !dbe_ddc_quantize?0:0:5119372:10874810:10885028:5120790:1939:-1924:7;
- !dbe_ddc_quantize?0:1:5123976:10875742:10877565:5122717:2120:-2120:0;
- !dbe_ddc_quantize?0:2:5120918:10872384:10881606:5125092:2287:-2289:-1;
- !dbe_ddc_quantize?0:3:5120706:10877426:10886561:5115307:2229:-2230:0;
- !dbe_ddc_quantize?0:0:5123182:10869125:10883316:5124377:2088:-2091:-2;
- !dbe_ddc_quantize?0:1:5126434:10870508:10877552:5125506:2042:-2043:0;
- !dbe_ddc_quantize?0:2:5123684:10870278:10878195:5127843:2006:-2007:-1;
- !dbe_ddc_quantize?0:3:5120673:10870464:10887511:5121352:1960:-1961:-1;
- Then 60 secs of data was taken tracking blank sky.
Looking at the data
- logged at oper@mk6 to get the data.
- The raw files were combined with vsb_fs. the combined file
was:
- ~oper/data/tmp/t006_aa_no0001/t006_aa_no0001
- The combined (but not vmuxed) files were copied to
gpuserv0:/media/DATA0/phildata/vlbi/211018/ 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 t006_aa_no0001/t006_aa_no0001 5032 1600
0,1,2,3,4,5,6,7 t006_aa_no0001.vmux
- arguments:
- samples/frame= 5000bytes*(8bits/2bits) = 20000
- sec/frame=1/32MHz * 20000 =.000625seconds
- frames/sec=1/.000625=1600 frames/sec/chan
- m5spec.py t006_aa_no0001.vmux VDIF_40000_512_8_2 1000
16384
- arguments
- 40000 bytes data/frame. since we put 8 5000 byte
frames in 1 frame
- 512Megasmp/sec: 32MhzSampling*2bits*8chan=512.
- 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)
There is no longer a problem with the headers.
The voltage distribution and the spectra.
In idl
- 8192 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 2
experiments:
- t006
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 8543 MHz) is showing up at + 11MHz
in the 8532 MHz band
- Page 2: voltage histograms:
- The 8192 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 .945 digitizer levels. This is correct
for integer values.
Summary
- 8 frequency bands of 16 Mhz each were output
correctly.
- We saw the 8543 MHz tone 11 MHz from the edge of the 8532
Mhz band
- The quantize routine that is being used to set the
quantize levels is doing it correctly.
- The test was done in evn mode using recorder=
flexbuf:mk6 (in the vex2snap command).
processing:x101/211018/fstest.pro