cband wide (4 to 8 ghz)
aug17
The cband wide receiver covers 4 to 8 GHz.
It has a linear omt followed by hybrids (in the dewar) to convert to
circular polarization. The cal values are injected after the hybrid
and before the first lna.
The receiver was installed in jul17.
The wide (4GHz) bandwidth needs the 10Ghz
upconverted mixer to be able to cover the entire band (the 1
GHz if1 bandwidth would require the LO inside the rf band if the
2-12 GHz mixer was used to cover the entire band).
Sections:
History
Recent
system
performance measurements
Daily
monitoring
of Tsys
Dewar
temperatures
Calibration measurements
commisioning
All measurements in date order
Misc
History:
- 170427: cals measured on sky at the antenna test building.
- 1707xx: installed in dome
- 170809: first data taken. turret=162, model offsets:
-34.20 -145.37
- 170815: horn moved downhill .628 inches (all it would go).
model offsets:-34.20 -122.86
Calibration
measurements:
All
measurements in date order
170809: manually track
sources to get initial pointing offsets.
170810: initial power levels measured with
upstairs if1 power meter.
170810: cal values
measured on hilltop 27apr17. (includes flange temperature)
170811: calibration scans
at original horn position
170814: moved horn uphill
.391 inches (wrong direction, got my sign wrong :) )
170815: moved horn downhill
from original position .628 inches, then more calibration scans.
170810: Initial measurement of the if1
power levels.
The cbw power levels were measured using the
if1 power meter (upstairs before the fiber optic
transmitter). For the 1 Ghz bandwidth, the optimal value
measured on the power meter should be -33 dbm (the meter has a
20db pad in front of it).
The setup was:
- the 10 GHz upconverter was used for the measurement.
- The dome was at za=1.5 degrees.
- power measurements were made from 4000 to 8000 Mhz in 100 MHz
steps
- At each step the 1 ghz mixer outputbandwidth was measured at
the center frequency.
- The RF and IF attenuators were set to 0 db attenuation.
- The cycle was repeated twice.
The plots show the measured IF1 power
vs frequency (.ps) (.pdf):
- Top frame: Measured power vs frequency.
- black: polA,red PolB, green line optimum value
- Since the rf and IF attenuators were set to 0, the values
below the green line could not be adjusted to the optimum
value.
- Bottom Frame: power vs freq after adding 9db gain to polA and
5db gain to polB
- The power spectra now sits above the optimum value.
- the purple lines are 1db steps above the optimum value.
- For each freq it is now possible to adjust the level to the
optimum value using the rf attenuator:
- 5000 : set rf atten to 7db
- 6000: set rf atten to 5,4 db for polA,B
- 7000: set rf atten to 3,2 db for polA,B
- 8000: set rf atten to 0,0
- The rf attenuators go 0 to 11 db . this gives 4db head room
for 5000 Ghz . (if needed there are 11 more db in the IF1
attenuators.
Summary:
- add 9db gain to polA, 5 db to polB in the cbw postamp chassis.
procesing: x101/170810/cbwtest.pro
Misc
180209 - path of 2018cb asteroid across the
dish
The plot shows the az,za track
of asteroid 2018cb and well as the az,za rates (.ps) (.pdf)
The is similar to a 34 deg dec source moving
backwards across the sky.
processing: x101/180207/checkephm.pro
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