APPENDIX: GBT Prime Focus Receivers
| Receiver |
Center f(GHz) |
Fsky (GHz) |
waveLen(cm) |
FWHM |
est.Tsys |
IF1 (GHz) |
| PF1.1 |
0.3425 |
0.290 - 0.395 |
88 |
36' |
30 K |
1.080 |
| PF1.2 |
0.450 |
0.385 - 0.520 |
66 |
27' |
30 K |
1.080 |
| PF1.3 |
0.600 |
0.510 - 0.690 |
50 |
21' |
30 K |
1.080 |
| PF1.4 |
0.800 |
0.680 - 0.920 |
37 |
15' |
25 K |
1.080 |
| PF2 |
1.070 |
0.910 - 1.230 |
28 |
12' |
25 K |
1.500 |
For calibration data, use the "rcvrCalibView" program to display
recent and earlier data.
All prime focus receivers have one beam and two polarizations.
Either dual linear or dual circular polarizations may be selected.
The first stages of the receivers are cooled FET amplifiers.
The feeds for bands 1-3 (0.290-0.690 GHz) are short-backfire dipoles.
The feeds for bands 4 and 5 (0.68-0.92 and 0.91-1.23 GHz) are
corrugated feed horns with orthomode transducers (OMT) to split
the polarizations.
Receiver Changes:
- The four bands of PF1 are all in the same receiver box,
but use different feeds. A feed change is required to
move between bands, which takes 2-4 hours.
- Changing from PF1 to PF2 or vice-versa takes about 4 hours.
IF conversion:
First LO setting (LO1) :
LO1 = Fsky + IF1
- (using IF1=1.08 Ghz as in above table)
LO1 range for PF1 :
1.36 to 2.01 GHz, with 1 Hz resolution.
Filters:
Following the IF1 conversion,
bandwidths 240, 80, 40, or 20 MHz may be selected.
Attenuators:
Attenuator settings of 0 to 64 db in steps of 0.5 db can be selected.
These provide the correct power levels for the optical fiber drivers,
and are not normally set by the user.