Testing the QRFH on the telescope:jun22


QRFH power levels on telescope (warm receiver)
check the pointing with crosses on the moon
Tsys using on,off the moon
sefd using on,off on CasA
sun: on/off position switch and cross.

wideband receiver main page



    Hamdi mani brought a wide band QuadRidgeFlaredHorn (QRFH) to arecibo during jun22. It was tested on the 12meter using a warm receiver and the field fox spectrum analyzer.

Data taking routines to drive telescope and fieldfox

    the tcl  datataking scripts are in /share/obs4/usr/p12m/wbrcv/

Timeline of what we did.

log periodic ant (1-10GHz) on camera tripod looking at rfi all night long on pad next to 12meter
qrfh feed on camera tripod on pad next to 12meter
  • sky, absorber (yfactor) measurement
  • monitored rfi all night with qrfh feed pointing south.
qrfh feed installed on telescope
  • long cables from feed down to pedestal used.
  • y factor measurements
  • had lots of trouble with dynamic range from rfi.
  • onoff 3C274.. didn't see anything
  • elevation scan. step 10->80deg in 10deg steps. az=5
  • more testing trying to optimize dynamic range by changing the postamp amplifiers'
  • still had trouble with dynamic range
  • on,off position switch on CasA
Field fox moved  adjacent to the feed. solved the dynamic range problems
  • yfactor measurements
  • onoff crab nebula
  • 2.8 GHz hipass filter installed
  • setup was:
    • lna->biasT->4ft cable->biasT->2.8GHz HiPassFilter -> fieldfox
      • fieldfox preamp in.
  • Horn at 21.6 inches (capton to apex of secondary).
  • azswings (stepping az,el)
    • horn at 21.6 inches, start 18:10
    • preamp on, FF attn set to 5db.
    • az :-90 to +270 deg with azstep of 45 deg. 4 elevations starting at el-8deg then stepping by 25 deg in el.
    • 20 recs/position
    • cmdfile: onoff_moon_220617.tcl
  • on,off position switch on moon.
    • 2 days after full moon., el 41 to 37 deg. start 04:59 am.
    • preamp on, attn=0
  • on,off position switch on casA . start 5:45 am
    • attn=0,preamp on, 4 on,offs done.
  • on,off position switch on sun. 14:44 -> 15:32 ast
    • 2 on,offs done
  • elevation steps. start: 18:57
    • az=5, el 10->80 deg i 10deg steps.'
  • cross on moon
    • 11 points/strip. -50 to +50 amin in 10 amin steps
      • only got az strip
  • cross on sun
    • 11 points/strips -50 to _50 amin in 10 amin steps
      • only got az strip
  • azswings (stepping az, el)
    • preamp on, FF attn set to 5db.
    • -90 to +270 az using 24 deg az step. (10 recs/position)
    • step in el 8 to 68 deg in 20deg steps
  • el steps
    • el =10 to 80 deg in 5deg steps. az=180.
    • preamp on, attn=0
  • cross on casA start 23:54
    • 7 points/strips 10amin steps
    • 2 patterns , but only a strips ok.
  • cross on moon.
    • 11points/strips, 1 pattern, only az strip ok
  • on,off position switch on moon. 1 pattern.
  • Switched to 2.5 GHz hipass filter
  • azswings (drive in az, step in el)
    • -90 to +270 at .2 deg/sec.
    • 1 sweep of FF took about 6 seconds, so 1.2 degrees motion /spectra
    • el: 6 degrees to 81 deg in 5 deg steps
    • took about 8 hours.
  • cross on moon
    • preamp off, attn=0 (because of 2.5GHz hipass filter)
    • az and el strips ok, but off moon we are close to the ff noise floor.
  • Switched to no HiPass filter
  • azswings (drive in az, step in el)
    • -90 to +270 at .2 deg/sec.
    • 1 sweep of FF took about 6 seconds, so 1.2 degrees motion /spectra
    • el: 6 degrees to 81 deg in 5 deg steps
    • took about 8 hours.

 Check the pointing with crosses on the moon.

    Crosses were done on the moon to check the pointing of the system.

The crosses  had:

Data was taken on:

Processing the data:

    Try and exclude freq channels that have rfi when computing the total power.
    For each of the 11 points in a strip:

    For each strip:
    compute the total power for each point of a strip.

    Fit a Gaussian to each strip

The plots show the results of the crosses on the moon (.ps) (.pdf):

Fit values:

fwhm fit


processing: x101/220621/crosses.pro

Tsys using on,off the moon.

        On off position switching on the moon was done measure the system temperature. The moon is about 30 Amin. The beamwidth of the 12meter varies from 40Amin to about 8amin.


The plots show the results of the on,offs (.ps) (.pdf)


processing: x101/220617/onoff_moon_both.pro

SEFD using CasA

    On, off position switching on CasA was used to measure the SEFD (System Equivalent Flux Density.. or Tsys/Gain).
Data was taken on 17jun22. 4 on/off patterns were done. The crosses on the moon showed that the pointing error was not too large.

To compute the SEFD you need the flux of casA. Turns out the flux of CasA is changing with time.
2 separate flux  spectra were used:

The plots show the on,off spectra and sefd: (.pdf)

Using the tsys measured with the moon on,offs and the sky absorber measurements give the following aperture efficiencies:

Aperture Efficiency from CasA and Tsys  for Yfactor and moon.
Yfalctor Tsys

    The efficiency from the moonTsys is giving an efficiency that is higher than expected. The probably means the moon Tsys is too high.

processing: x101/220617/onoff_casa.pro

On off position switch on sun

    On 17jun22 we did 2 on off position switches on the sun. the setup was:

The plots show the on,off position switch results (.ps) (.pdf)

Were we pointing at the sun?

    On 18jun22 a cross was done on the sun (but only the azimuth strip was valid. The setup was:

The plots show the azimuth strip results (.ps) (.pdf)

    The pointing error of 5amin --> that the total power computation on 17jun22 is probably not biased by pointing errors.

processing: x101/220618/suncross.pro