cband wide (4 to 8 ghz)
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).
All measurements in date order
- 170427: cals measured on sky at the antenna test building.
- 1707xx: installed in dome
- 170809: first data taken. turret=162, model offsets:
- 170815: horn moved downhill .628 inches (all it would go).
model offsets:-34.20 -122.86
170809: manually track
sources to get initial pointing offsets.
measurements in date order
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
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
- 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
- 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
- add 9db gain to polA, 5 db to polB in the cbw postamp chassis.