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X-band Receiver

X-Band Receiver
Basic Information

Recent Events

Calibration & Beam Parameters

RFI Situation

Pointing

Technical Description

Receiver History

Contact Info

 

 

 

1. Basic Information:

 

Frequency Range (GHz): 8.0 - 10.0 GHz*

Name and Number:

X-Band (cb, 11)
Measured Sensitivity (K/Jy): 1.5 - 5.0 (8.5 GHz)**
Measured System Temp (K): 50 - 55K**
Native Polarization: Dual Circular***
Beam Size (at 8500 MHz): ~30 arcsec

*Although the bandpass of this receiver is 2 GHz, only a 1-GHz wide chunk can be brought to the Control Room for processing at any given time.

**Note that these values depend upon the accuracy of the noise-diode calibration in estimating the system temperature and K/Jy. As well as being a function of zenith angle, the telescope sensitivity is presently also a function of azimuth There seems to be a rather strong difference between the measured Gain for sources transitting to the north and south of the zenith (Dec ~ 18.3 deg), with the latter giving the better performance (higher Gain, that is more symmetric about transit.) See calibration info below for a more accurate description of the telescope parameters.

***While the native polarization of the receiver is circular, linear polarization can be produced using the 180-deg hybrid present in the IF chain. If this is required, consult your Local Friend.

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2. Recent Events:

The X-band receiver sensitivity was improved considerably by the major adjustment of the primary surface of the 305-m Telescope, completed in September 2001. A further round of photogrammetry, to be followed by surface fine tuning, is presently underway. The X-band system also benefits considerably from the availability of the active tie-down system, allowing the best possible "dead-reckoning" focus adjustment (and eventually dome pitch and roll compensation). It is hoped that local focusing on strong point sources will eventually become available to users via motion of the tertiary reflector.

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3. Calibration & Beam Parameters:

Gain and System Temperature Cal Values Beam Maps
Polarization Calibration Schedule Misc. Calibration Info


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4. RFI situation:

 

X-band suffers some Radio Frequency Interference (RFI), which is believed to be due to aircraft communications. Daily RFI monitoring plots for the past several years from the Observatory "hill-top" monitoring system can be found in binders in either the telescope Control Room or by asking Rey Velez, the Arecibo Spectrum Manager.
  • For the current daily average X-band RFI plot from the Arecibo "hill-top" monitoring system, click here .

  • For the current frequency v time X-band RFI plot from the Arecibo "hill-top" monitoring system, click here .

  • For the current frequency v time X-band RFI plot (with band-pass correction) from the Arecibo "hill-top" monitoring system, click here .

  • For the current daily rms/mean v frequency X-band RFI plot from the Arecibo "hill-top" monitoring system, click here .

 

5. Pointing:


Soon after a pointing model has been established, and using the same pointing facilities as during the determination of the model, the total rms pointing is expected to be better or approximately equal to 5 arcsec, i.e. adequate for good-quality X-band measurements. As the elapsed time since determination of the model increases, additional engineering adjustments/modifications take place, or conditions are different to when the model was determined (e.g. should the active tie-down system become unavailable at any time), then the rms pointing is likely to be somewhat worse. In a recent C-band run where active tie downs were not available, but the platform was set to its best mean height, pointing was reported as being within 15 arcsec od perfect, i.e. below normally expected quality, and maginal for X-band operations. A typical set of C-band pointing curves acquired in Aug 01 by Phil Perillat are to be found here

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6. Technical Info:


To see a block diagram and photographs of this receiver, consult the engineering department's receivers page. There are also useful spectral plots of the power levels at the input to the IF/LO cabinet to be found there.

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7. Receiver History:

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8. Contact Info:

For further information on this receiver, please contact Chris Salter
(csalter@naic.edu)

 

 




Last updated: Friday, 03-May-2002 22:12:42 AST