VC rfi using spectrum analyzer (2016)

18may16

setup
Measurement table
plots of rfi
Summary


Intro:

    On 160414,160427,160506,160509 we measured the rfi coming from the new visitor center displays. The measurements were made at the visitor center using  a bfield probe as well as an lband helix. Data was acquired using the anritsu spectrum analyzer.
The display tested were:






Setup:


Table of measurements done:

The table below lists the measurements that were stored on the anritsu.

file
ant
measurement
date
notes
Omni globe


  • cpu, display screen
  • globe, projector for globe
  • positions: at cpu, and then at globe.
49
lb
cpu on, globe off
160414
at cpu
50
lb
all off
at cpu
58
lb
all off
at globe
59
lb
globe on, cpu off
at globe
60
lb
globe on, cpu on
at globe
61
lb
globe on, cpu on
obsDeck south rail
door closed
62
lb
globe on , cpu on
obsDeck south rail
door open
63
lb
globe off, cpu off
obsDeck south rail
door closed
64
lb
trace A:monOff, cpuOn
trace C: monOn,cpuOn
at cpu
75
lb
cpu on
160506
helix 1 meter from cpu, pointed at cpu
76
lb
cpu off
off for rec 75
crater machine


  • motor to turn turntable.. this is what we tested.
  • cpu,camera, display screen (not tested)
  • motor to move air gun in ,out..(not tested)
65
eprb
motor on, cpu on
160414 Eprb next to motor
66
eprb motor off, cpu on
Eprb next to motor
67
eprb motor on, cpu on
zero span
Eprb next to motor
atmospheric radar


  • large interactive display screen
  • cpu inside cabinet
68
lb all on
160414 helix 3 feet from display pointed at display
69
lb all off
same as above
70
lb all on (repeat 68)
same as above
Track an asteroid


  • cpu in cabinet (8 feet from display)
  • kinect motion tracker
  • projector
49
Bprb
kinect on
160427
large Hprobe perp to kinect window (vertical)
50
Bprb
kinect unplugged,projector still on.
same as above
58
Bprb
all off
same as above
77
lb
all on
160509
lband helix pointed at kinect output window, 1 meter away
78
lb kinect off
off for rec 77
radio freq in the sky (upstairs)


  • 3 touch screens, 2 cpu inside exhibit on floor.
  • posA - in front of screen that points toward stairs
  • posD - side of exhibit, door open, between two cpus on the inside
59
lb
all on
160506
posA: helix 1 meter from screen, pointing at screen
60
lb
all on
polD: 1 meter from side door pointed at cpus.
61
lb
all off
posA: off for rec 59
62
lb
all off
posD: off for rec 60
63
Bprb
all off
posA: large loop, vertical, loop perp to screen
64
Bprb
all off
posD: probe vertical between 2 cpus
65
Bprb
all on
posA: on for rec 63
66
Bprb
all on
posD: on fro rec 64
Deep sky detective (upstairs)


  • touch screen and cpu under display
  • posA: in front of display
  • posB: next to cpu (under display)
67
Bprb
all on
160506
PosA. large loop, vertical, perp to screen, next to screen
68
Bprb
all on
PosB: next to cpu
69
Bprb
all off
PosA: off for rec 67
70
Bprb
all off
PosB: off for rec 68
71
lbnd
all off
posA: lband helix pointed at screen, 1 meter away
72
lbnd
all on
PosA: on for rec 71.
arecibo telescope model(downstairs)


  • motor to turn azimuth
  • motor to move in za
  • motor to move catwalk ?
  • posA: lband helix at plexiglass window, pointed at az,za motors.
73
lbnd
moving azimuth
150506
PosA:lband helix
74
lbnd
no motion
PosA: off for rec 73






Plots of the data

Exhibit
plots
description
Globe
.ps .pdf
  • We used the lband helix for the measurements.
  • Page 1: 160414
    • Top: lband helix at cpu (about 3 feet away):
      • black: single trace (no averaging) cpu, globe on
      • red: peak hold (about 30 secs),  cpu,globe on
      • green: peak hold, all off
      • There is a comb: 121.92 MHz spacing, includes: 1217.62539 (from hi res measurement)
    • Bottom: helix at globe (about 3 feet from projector).
      • black: single trace (no averaging), cpu, globe on.
      • red: peak hold (30 secs), globe, cpu on
      • green: all off
      • The projector for the globe is not creating much rfi.
  • Page 2:
    • Top: over plot globe cpu rfi 14APR16 and 06may16
      • Red, green: on,off globe cpu: 14APR16
      • blue,lightblue: on,off globe cpu: 06may16
      • helix at visitors deck (at rail) looking bad at exhibits
      • The comb was present on both days
      • the pairs of rfi around:
        • 1150, 1275, 1400, 1750
        • also repeat on the two days.
    • Bottom: high plot of globe cpu on,off from visitor center balcony
      • the door to the outside balcony was closed
      • The resolution bandwidth was 10 Hz.
      • -152 dbm in 10Hz bandwidth is equivalent to a Tsys of about 4000 Kelvins.
      • The 1217.62539 MHz birdie from the cpu is around -131 dbm (in a 10Hz channel)
      • The spectrum analyzer was free running..
Processing: x101/160414/rfiVc_globe.pro
crater
.ps
.pdf
Make a crater display:
  • We used the efield probe placing it next to the motor that turns the turntable
  • top: motor on,off .. spectra
    • red is peak hold (30 secs) with motor on
    • green: peak hold (30 secs) with motor off (cpu is on).
    • this motor makes lots of noise.. it must have brushes
  • Bottom: eprobe at motor, zero span (time domain).
    • the resolution bandwidth was 3MHz centered at 327 MHz
    • The x axis is in milliseconds. It shows when the narrow spikes from the motor occurred.
    • The time resolution is 18usecs. Most of the spikes were not resolved with this time sampling.

Processing:x101/160414/rfiVc_crater.pro

atmradar
.ps
.pdf
atmospheric radar display
  • lband helix, pointed at monitor (3 feet away).
  • Red: peak hold all on
  • green: peak hold, all off
  • blue:Repeat peak Hold all On... the on rfi repeated.
  • I've flagged some of the stronger peaks.
Processing: x101/160414/rfiVc_atm.pro
radarTrack
anAsteroid
.ps
.pdf
Track and asteroid display.. kinect unit and projector
  • Top: 0 - 1000 MHz
    • large Hfield probe was placed perpendicular to the kinect window
    • Black: peak hold all on
    • red:   peak hold, kinect Off, projector still on
    • green: all off
    • rfi below 300 MHz (may be from projector)
  • Bottom: 1000 to 2000 MHz
    • lband helix pointed at kinect window. 1 meter away.
    • Lots of rfi. It might have been sweeping across the band...
Processing: x101/160414/rfiVc_trkasteroid.pro
AO model
.ps
.pdf
AO telescope model
  • lband helix at plexiglass window.
  • take data with azimuth moving and stopped
  • Lots of rfi from the motor.
Upstairs displays:
RadioSky
.ps
.pdf
Radio sky display: 3 interactive monitors, cpus inside display
  • PosA: looking at display facing the stairs
  • PosB: side of display open , looking at cpus.
  • Page 1: lband helix: 1-2 Ghz
    • Top: posA, 3 feet away pointed at display. display on,off
    • Bottom: posB, 3 feet from cpus, pointed at cpus. display on,off
  • Page2: large Bfield loop. 0 to 1 Ghz
    • Top: posA. at Display. Probe vertical, loop Perpendicular to display
    • Bottom: posB: hanging between the 2 cpus
  • 74.198 MHz comb with odd  harmonics strongest
  • 1483.6  is the strong comb element in 1-2 ghz (at least using our helix).
processing:x101/160414/rfiVc_radioSky.pro
deepSky
detective
.ps
.pdf
Deep sky detective display.
  • Display and CPU
  • PosA: in front of display
  • PosB; next to cpu.
  • Page 1: 0..1000 MHz large bfield loop
    • Top: probe vertical, loop perpendicular to screen (at screen)
    • Bottom: probe next to cpu. Not much rfi from cpu
  • Page 2: 1000 to 2000 MHz. lband helix
    • helix 3 feet from display
    • flag 73.272 MHz comb.. 1320.7 strongest comb element in lband
    • also flag 149.12 MHz comb (or half that).
      • 1485.4 is strong birdie in lband
processing: x101/160414/rfiVc_deepsky.pro




Summary:

ToDo:




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