800 MHz receiver

sep08

     The 800 MHz is a dual polarization (linear pols) cooled receiver (tsys about 120K) covering 700 to 800 Mhz. There is a low loss cavity filter in front of the dewar to cut out adjacent tv stations(below 700 Mhz)  as well as the cell band (above 800 Mhz).

History
Recent system performance measurements
Calibration measurements
All in time order
 


History


Calibrations

26sep10: calib run byu antenna after reinstallation.
11jan10: BYU antenna. compare the Penn state.
29jun-02jul09: calibration runs old cal coupler (.ps) (.pdf)    processing: x101/090630/calib.pro


Miscellaneous:

14mar11: updated pointing model to correct for az,za offsets
11mar11: added results of stokes calibration (jan,mar11).
08mar11: Dual pol bandpass shape, rms/mean, and sefd vs freq.
08mar11: alfa motor controller, dome cameras rfi at 750 Mhz.
29nov10: azimuth dependence of 800 rcvr rfi.
29nov10: az swing looking at 734.7-739.3 Mhz rfi
24nov10: 734.7-739.3 Mhz rfi in band
30sep10: a2524 dps shows larger ripple in polA.
26sep10: calib run byu antenna after reinstallation.
11jan10: BYU antenna. compare the Penn state.
12oct09: 800 Mhz receiver band pass:
17sep09: PolB/PolA ratios for Tsys,Gain,SEFD jul09->14sep09.
25aug09: azswing looking for chn 67 peak after chn turnoff. 
14aug09: new 800 Mhz receiver cals measured 13aug09
12aug09: tv channel 67 turns off
10aug09: beam squint in 800 Mhz rcvr
10aug09: double position switching shows rms polB > rms PolA.
29jun-02jul09: calibration runs old cal coupler (.ps) (.pdf)    processing: x101/090630/calib.pro
18jun09: freq hop 750/753.7 . Source of rfi in 700-800 Mhz.
14jun09: az swing looking at 700-800 Mhz.
17jun09: ripple appears in 800 Mhz rcvr polB
16jun09: calibration run 800 MHz rcvr with room temperature dewar.
13jun09: first look at 800MHz feed with tv stations off.
13apr09: 2 azswings near 820 MHz.
11apr09: chan 63/67: lower tv power stations seen in the 700-800 MHz band
08apr08: 2 azswings looking for chan62/50 peak values.
02apr09: planned usage of the 700 MHz band by emergency services
18dec08: spectral scan 620-890 MHz.
30oct08: look at hilltop monitoring data for oct08
05sep08: az strips at different turret positions to find correct turret center.

08mar11: dual pol bandpass. rms, and  sefd vs freq

    60 second on off position switching was done using the 800 Mhz rcvr on 08mar11.
The setup was:
The plots show the bandpass, stability, and sefd vs frequency (.ps) (.pdf):
processing: 110308/800calib.pro


26sep10: calib run with byu antenna

    On 24sep10 the 800 Mhz rcvr was reinstalled with the byu version 1.0 antenna. A calibration run was done  on 26sep10.
the plots show the calibration run results (.ps) (.pdf):
processing: x101/100926/800calib.pro


11jan10 single pol BYU antenna gain,tsys,sefd,beam testing (top)

    The penn state dual pol antenna was replaced with a single pol byu antenna on 22dec09. On 11jan10 calibration scans were done on the source B0618+145 to check it's performance.
    The plots show the antenna performance (.ps) (.pdf):
SUMMARY:
processing: x101/100111/800.pro

12oct09 800 Mhz receiver band pass:  (top)

    An average bandpass for the 800 MHz receiver was measured on 12oct09. The setup was:
The plots show the averages bandpass for the 800 MHz receiver (.ps) (.pdf):
Some of the spikes are coming from:
processing: x101/091019/800bp.pro

17sep09: 800 Mhz rcvr PolA, polB ratios jul-sep09  (top)

    The x102 calibration data was used to measure the performance of polA versus polb for the 800 Mhz rcvr. Data from 2jul09 thru 14sep09 was used. The polA, polB data was  extracted from the stokes I,Q measurements.

    The plots show the 800Mhz  rcvr performance and polB/polA ratios (.ps) (.pdf):
Conclusions:
processing: x101/090917/chkpols800.pro

25aug09: azswing looking for chn 67 peak after chn turnoff.  (top)

     Chn 67 (789.25 video carrier) turned off on 12aug09. We continued to see a residual signal at the video and audio carriers. It was not coming from the old chn 67 because the people at the station told us that the transmitter had been dismantled.
    On 25aug09 an azswing was done to find the azimuth of the peak value of this signal. The setup was:
The plot shows the azimuth dependence of chn67 video and audio carrier (.ps) (.pdf):
The video peaks at az=-46 (or 314) degrees. There is also some power around 40 and 60 degrees. These directions given the maximum power scattered into the dome. They are not necessarily the directions toward the transmitter.
processing:x101/090825/azswing.pro

10aug09: beam squint in the 800 Mhz rcvr (top)

    The calibration data from 28jun09-02jul09 was used to measure the beam squint in the 800 Mhz rcvr. The plot shows the beam squint amplitude vs the amplitude of the beam squint (.ps) (.pdf):
processing: x101/090810/bmsquint.pro

23jun09: rfi in the 800 Mhz rcvr  (top)

    To measure rfi in the 800 Mhz rcvr to tests were done:

az swing on 14jun09:

    The setup was:
Dynamic spectra for clockwise azimuth swing (.gif):
The azimuth dependence of the various birdies in the band (.ps) (.pdf):


17jun09: ripple appears in polB (top)

    A ripple appeared in polB of the 800 Mhz Receiver. The timeline was:
The  plots show the appearance of the ripple in polB (.ps)  (.pdf):
Date taken on 18jun09 at various times and configurations continued with the ripple in polB.

processing: x101/090617/polB_bad_800.pro

16jun09: calibration run 800 MHz receiver. (top)

    A calibration run was done using the 800 MHz receiver on 15,16, and 17 jun09.The status of the feed/receiver was:
    The plots show the system performance for the 800 MHz rcvr (.ps) (.pdf):
processing: x101/090616/calib800.pro

13jun09: tv station turn off date, rfi, and calib. (top)

    The new crossed dipole feed was installed in the dome on 12jun09 with the cavity filters in front of the dewar. The dewar was still room temperature, and the filters after the dewar are not yet installed.
   
    Data was taken for 60 seconds with the mock spectrometer. The setup was:
    The plots show the bandpass and rfi in the band (.ps) (.pdf):

    The second plots are from a short calibration run (.ps) (.pdf) on B0758+143 (4.7 Jy @ 740 MHz).
SUMMARY:
processing: x101/090613/calib800.pro, mock800.pro

13apr09: 2 az swings looking at 820MHz band (top)

    Two azswings were done the with 800 MHz test rcvr on 13apr09 with the dome at 19 degrees. The filter was set to 820 MHz to see how strong the interference in the high side of the 700-800 MHz band is. This will determine how  fast the filter in front of the dewar will have to fall off on the high side.
The setup was:
Dynamic spectra for the two azimuth swings (.gif):
Peak and mean spectra for az swings (.ps) (.pdf):

Summary:

processing: x101/090413/azswing.pro

11apr09: chan 63,67:low power tv stations in the 700-800 MHz band  (top)

    The following low power stations have been seen in the 700-800 MHz band using the test rcvr. As of 23jun09 they are still broadcasting in the band.

chan
freq
notes
63
764-770
  • W63BF 42 km west of ao, 1.79 km south. translator station for wccv-tv yiyi avila channel  46
  • video carrier avg azswing value 44 db above average tsys.
  • Peak value > 50 db above tsys (using 21KHz rbw). This was at an az= -16 deg.
  • Has an fcc license for 35.6kw analog transmitter see chan 63 fcc info (.ps)
  • This station has not filed a statement with the fcc to terminate transmissions on 12jun09.
  • lat/long of xmiter: 18:19:31/67:10:13
  • fcc contact info/owner (.ps)
  • Seen in detail in azswings 08apr09.
67
788-794



08apr09: azSwings for chan62/50:Where to put the 800 MHz filter. (top)

    The 800 MHz receiver will cover the 700-800 MHz range after the  the Tv stations in this range are  transitioned to lower frequencies (on 12jun09).

    A bandpass filter in front of the dewar is needed to:
We would like to push this filter as close to 700 MHz as possible to give more suppression for the cell phone band.

    The tv stations closest to the bottom of this band after 12jun09 will be:
    On 08apr09 2 azimuth swings were done to see how strong channel 62 is above the current receiver (not cooled) noise floor. When it switches to channel 50, it will most likely stay on the same tower. The setup was:
Dynamic spectra for the two azimuth swings (.gif):
Plotting the spectra vs frequency  (.ps) (.pdf):

Summary:


chan
freq
Notes:


lat/long AO: 18:20:39.44/66:45:10
50
686-692
Peaks 35 db above noise floor (from chan 62 measurements)
51
692-698
  • WRFB 60 miles east of AO.
  • Currently broadcasting analog on channel 52 (see below). Will switch to chan 51 on 12jun09.
  • Has fcc licencse for 256 KW ERP digital transmitter: see chan 51,52 fcc info (.ps)
52
698-70
  • will move to chan 51 on 12jun09.
  • 18dec08 spectral scan saw video carrier at 7 db above avg Tsys.
  • May be stronger since did not do an azswing.
  • Current license is 275 KW ERP analog transmission.
  • lat/long of xmter: 18:16:44/65:51:12
63
764-770
  • W63BF 42 km west of ao, 1.79 km south
  • video carrier avg azswing value 44 db above average tsys.
  • Peak value > 50 db above tsys (using 21KHz rbw). This was at an az= -16 deg.
  • Has an fcc license for 35.6kw analog transmitter see chan 63 fcc info (.ps)
  • This station has not filed a statement with the fcc to terminate transmissions on 12jun09.
  • lat/long of xmiter: 18:19:31/67:10:13
processing: x101/090408/pdevazswing.pro


02apr09: Emergency services usage of 700 MHz band (top)

    Emergency services have been allocated 24 MHz of bandwidth in the 700 MHz band. They will begin using this bandwidth after the dtv transition (jun09).
    The band usage  is described here (.ps) (.pdf):
The entire report: Federal Strategic Spectrum plan (march 2008)  is found on the ntia office of spectrum management page.


18dec08: spectral scan 620-890 MHz. (top)

    Data was taken with the low frequency rfi feed (650-900 MHz) on 18dec08 around 16:00 hours. The setup was:
Tsys in cal units:
   
the first plots show tsys in units of th cal (.ps) (.pdf):
Spectral scan of 620 to 890 MHz.
    The second set of plots shows the spectral scan from 620 to 890 MHz (.ps) (.pdf):
A tour through the stronger rfi:

Things to check out:

processing: 081218/rfifeed.pro

05sep08: looking for the turret position. (top)

    The source B1607+268 (1") was used to find the correct turret position for the 800 MHz feed. The procedure was:
The setup was:
The plots show the az strips thru the source for the various turret positions (.ps) (.pdf):

The new turret position was taken to be 188.5. The old position of 182.7 has very uneven sidelobes. We should probably redo this test with a stronger source starting at 188.5 as the center and moving up and down in turret position to verify that this is the real center.

The pointing model has not yet been updated for this change.
processing: x101/080905/rfifeed.pro

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