Links:
intro
setup
datataking
Spectra at field fox  for all 3 filter configurations.
Azimuth dependence of rfi using spectra at horn output
Total power vs azimuth to check for lna compression.
Summary

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INTRO

    The QRFH was mounted on the 12meter and tests were done to measure the power levels using different hi pass filters. We wanted to see if a hi pass filter was needed before the lna in the cooled system. The tests were done 16 -> 21jun22.

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SETUP

• QRFH horn mounted at the focus of the 12 meter.
• The mouth of the horn  was 21.6 inches from the center of the secondary for these measurements.
  
• 44 db gain amp mounted at output of QRFH horn
• 9916 field fox spectrum analyzer was used to measure the levels.
• We initially tried using the  sband cables to bring the signal down from the horn to the pedestal.
• The loss in the cables was limiting the dynamic range we could achieve.
• The field fox was then mounted up close to the horn.
• An ethernet cable was strung from the field fox to the pedestal so we could remotely control the field fox.
  
• The signal path was:
• QRFH -> 3" cable -> 44db amp->biasT-> 4 foot cable ->biasT->HiPass filter -> field fox
• the biasT's were used to power the amp.

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Data taking

    Data was taken on 4 days

• 16jun22:  2.8 GHz hi pass filter
• step in azimuth and then step in elevation
• az: -90deg to 270 deg in 45 Deg steps after 1 rotation, step in elevation
• el:  8, 33, 58, 83 degrees
• FieldFox setup
• 2-12 GHz span, 1Mhz rbw,vbw=rbw, 10001 points, pwr detector, pwr avg sweeps
• preamp on, attn=5db
  
• avg 3 sweeps, output, then repeat 20 times. at each position.
• 18jun22: 2.8 GHz hi pass filter
• step in azimuth and then step in elevation
• az: -90 to +270 in 24 deg az steps then step in elevation
• el: 8,28,48,68 degrees
• Field fox setup:
• 2-12 GHz span, 1Mhz rbw,vbw=rbw, 10001 points, pwr detector, pwr avg sweeps
• preamp on, attn=5db
  
• avg 3 sweeps, output, then repeat 10 times. at each position.
•  i doubled the number of az positions from 16jun22, so halved to number of output records.
• 20jun22: 2.5 GHz hi pass filter
• drive continuously in azimuth, step in elevation
• az -90 to 270 at .2 deg/second
• a field fox sweep took about 6 seconds , so the telescope moved 1.2 degrees during  a single sweep.
• the telescope beam varies from 40amin to about 10amin .
  
• the telescope moved 2 to 7 beams during a sweep.
• el: step  6 deg -> 81 deg in 5 degree increments.
• Field fox setup:
• 2-12 GHz span, 1Mhz rbw,vbw=rbw, 1001 points, pwr detector
• preamp off, attn=0db
• No sweep averaging. output to disc each sweep (which took about 6 seconds)
• it took 30 min/rotation. 8 hours in total.
• 12:20 ->20:22 hours
  
• 21jun22:  no hipass filter:
• (same as 20jun22)
  
• drive continuously in azimuth, step in elevation
• az -90 to 270 at .2 deg/second
• a field fox output took about 6 seconds , so the telescope moved 1.2 degrees during  a sweep
• the telescope beam varies from 40amin to about 10amin .
  
• the telescope moved 2 to 7 beams during a sweep.
• el: step  6 deg -> 81 deg in 5 degree increments.
• Field fox setup:
• 2-12 GHz span, 1Mhz rbw,vbw=rbw, 1001 points, pwr detector
• preamp off, attn=0db
• No sweep averaging. output to disc each sweep (which took about 6 seconds)
• 30 minutes per rotation
• 14:40 -> 22:45 hours
• Notes:
• 16,18 jun22 has 10001 points of 1 MHz rbw covering 10 GHz.
• to compute total power, just add up all of the spectra channels
• 20,21 jun22 had 1001 points of 1MHz rbw covering 10 GHz.
• power detect mode was used
  
• there were 10 sampled points for every output point.
• The detector would average the power of these 10 points before outputting
• To get total power,add up all the spectral channels then multiply by 10.
• I verified this when measuring the field fox noise floor with a  50ohm load with  both setups.

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Plotting the FieldFox spectra during the az,el motion

   The spectral density vs  azimuth,el motion is plotted for each day.

• For the azimuth steps
  
• 20 3 sweep averages are output for each position.
• The plots input the 20 records and display the average of the 20 recs
• For the azimuth swings:
• a single spectra is output every 1.2 degrees. No averaging is done.
• For the plots i interpolated each freq channel to 1 deg azimuth spacing.
  
• The plots show the spectral density at the input the to field fox (after the 40db of gain)
  

2.8 GHz hipass filter spectra (.png)

• 10001 pnts of 1MHz rbw across the 10GHz
• Each color is a different location
• The red spectrum at the bottom of the plot is the field fox noise floor with a 50 ohm load.
• The strongest spike is around 6.4 GHz (probably a point to point microwave  link)
• The 44db amplifier gain falls off above 10GHz.
• Top Frame: 16jun22
  
• azimuth -90 to 270 in 45 degree steps.
  
• el 8, 33, 58, 83 degrees
• average the 20 3swp average spectra at each position.
• bottom frame: 18jun22
• az -90 to 270 in 24 degree steps.
• el: 8,28,48,68 degrees
• azimuth -90 to 270 in 45 degree steps. step in el 8, 33, 58, 83 degrees
• average the 10 3swp average spectra at each position.

2.5 GHz hipass filter spectra (.png)

• 1001 pnts of 1MHz rbw across the 10GHz
• The field fox averaged 10 samples for every output  point.
• i did not increase the spectral density by 10db.
• az swing -90 to 270 at .2 deg/sec, el 6 -> 81 deg in 5 deg steps.
• Some of the 2350 MHz birdies are getting through the filter.
  

no hipass filter spectra (.png)

• 1001 pnts of 1MHz rbw across the 10GHz
• The field fox averaged 10 samples for every output  point.
• i did not increase the spectral density by 10db.
• az swing -90 to 270 at .2 deg/sec, el 6 -> 81 deg in 5 deg steps.

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Rfi from az swings with no hiPass filter (at horn output)

    The az swing spectra taken with no hi pass filter on 21jun22 were used to check the power levels and rfi vs az and el.
Each field fox spectra had the gain of the system removed so the spectral density was at the output of the QRFH.
The azimuth swings went from  6 to 81 deg elevation in 5 deg steps.

The field fox was set to:

• 2 to 12 GHz (10 GHz span)
• 1 Mhz rbw, detector mode=pwr avg
• 1001 points
• there are 10 rbw's  averaged for each displayed point.
• The spectra and total power from the field fox were multiplied by 10 to correct for this.
  

The first set over plots the spectra from each azimuth swings and then blowups in freq (.ps) (.pdf)

• Each color is an azimuth swing at a different elevation.
• The red line at the bottom is the field fox noise floor referenced to the horn output level.
• Page 1 covers the entire frequency band. Pages 2-6 are blowups in freq around areas that show rfi.
  
• Page 1: 2000-1200 MHz spectra:
• top: peak  hold spectra for each azimuth swing
• middle: average spectra for each azimuth swing
• bottom: min hold spectra for each azimuth swing.
• Page 2: 2000 - 3000 MHz .  rfi at:
  
• 2100 -2200 aws1,aws2,aws3 (Advanced Wireless serivices)
  
• 2320-2345 siriusxm radio satellite.
  
• 2340-2355  aws2 (at&t)
• 2400-2500   ism band
• 2500-2700  brs-ebs BroadbandRadioServices-EducationalBroadbandService
  
• Page 3: 3000-4000 MHz
• 3000-3050 (pico del este radar?)
• 3550-3700 citizens broadband services
  
• Page 4: 4000-5000 MHz
• 4690-4710
  
• Page 5: 5000-6000 MHz
• 5150-5850  U-NII band (internet providers)
• Page 6: 6000-7000 MHz
• 6370-6400  Probably a microwave link

dynamic spectra from the azimuth swings

    The table below shows the dynamic spectrum (spectral density vs azimuth, frequency) from each   azimuth swings

• Each image holds az swings from 2 different elevations

• elevations (deg)	dynamic spectra
  6,11	.png
  16,21	.png
  26,31	.png
  36,41	.png
  46,51	.png
  56,61	.png
  66,71	.png
  76,81	.png

 Notes on dynamic spectra:

• 2100-2200 rfi .. seen 0 to 360 deg.
• 3550-3700 rfi  .. seen 0 to 360 deg.
  
• 6370-6400
• present az= 0 to 280 deg up to elevation 56deg, then cover 0 to 360.

Rfi azimuth dependence

    The plots shows the azimuth dependence of various rfi regions seen in the data (.ps) (.pdf)

• The average  power around each rfi region was computed.
  
• The values from each azimuth swing where then over plotted.]

• Page	frame	freq Range	Notes
  1	top	2100-2200	constant large level all az A few peaks el=6: az=135,200,275
  	bottom	2340-2355	constant large level all az el=6 peaks at 135,200 az
  2	top	2500-2700	constant level in az
  	bottom	3550-3700	peak el=6 at az=175deg
  3	top	4695-4705	peak at az=200, el=6
  	bottom	5075-5800	u-nni band. az 100 to 200.. (looking at the transmitters on the mountain range)
  4	top	6370-6400	az=130. probably microwave link from utuado.

  
  

processing: x101/220622/plotspc_horn.pro

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Plotting the total power vs azimuth

The total power vs azimuth was plotted to see where the lna might saturate.

•  the power at the input the field fox was measured and plotted.
  
• The power at the output of the QRFH (by subtracting the gain of the system) was also plotted.
  

Total power vs azimuth showing  power levels at input to field fox (.ps) (.pdf)

•  These plots show the power measured at the input to the field fox (after the 40db of gain)
• topFrame: 2.8 GHz hiPass filter
• this data was stepped in azimuth and el.
• Each color is  data from a different elevation,
• + are data recorded 16jun22, * are data recorded 18jun22
  
• the largest value was -33.5 dbm around an azimuth of 135 and el=8 deg.
• Middle frame: 2.5 GHz hiPass filter.
• this data was driven continuously in az and stepped in el
• the computed value was increased by 10db because of the detector averaging 10 points.
• The maximum value was -12.6dbm at az=275, el=6 degrees.
• Bottom frame: no  HiPass filter
• this data was driven continuously in az and stepped in el
• The maximum power was -1.4 dbm at az=203 and el=6 degrees.
  

Total power vs azimuth showing  power levels at the output of the QRFH (.ps) (.pdf)

•  These plots show the power measured at the output of the QRFH
• Page 1: System Gain:
• Felix measured the s-parameters for the  system (short cable->amp,biasT,cable,biasT,filter).
• S21 (the gain) was then removed from the values that the field fox measured.
• the 3 colors show the gains for the 3 setups.
  
• There was 40db gain at the lower freq and fell to about 30 db at 10GHz.
• Page 2: power levels at horn output vs az,el
  
• topFrame: 2.8 GHz hiPass filter
• this data was stepped in azimuth and el.
• Each color is data from a different elevation,
• + are data recorded 16jun22, * are data recorded 18 jun22
  
• the largest value was -72.5 dbm around an azimuth of 135 and el=8 deg.
• Middle frame: 2.5 GHz highPass filter.
• this data was driven continuously in az and stepped in el
• the computed value was increased by 10db because of the detector averaging 10 points.
• The maximum value was -62.4 dbm at az=275, el=6 degrees.
• Bottom frame: no  HiPass filter
• this data was driven continuously in az and stepped in el
• The maximum power was -51.4 dbm at az=203 and el=6 degrees.
  

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Summary

    The total power vs az,el was measured for various az,el positions and hipass filter setups.

hiPass filter	maxPwr at fieldfox (dbm)	maxPwr AtHornOutput (dbm)
2.8 GHz	-33.5	-72
2.5 GHz	-12.6	-62.4
no filter	-1.4	-51.1

• We did not sample all azimuths so there may be spots a bit higher
• if the final cooled lna has a 1db compression level of -35dbm then we could probably get away with no filter.
• If the cooled filter noise contribution is low, we might think of using the2.5 GHz hipass filter.

processing: x101/220622/inpazdata.pro,plotazsw_ff.pro,plotazsw_horn.pro