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Decomissioned L-wide

Basic Information

Recent Events

Calibration & Beam Parameters

Available Filters

Technical Info

Receiver History

 

 

 

Basic Information:

 

Frequency Range (GHz): 1.12 - 1.73

Name and Number:

L-wide (lbw, 5)
Measured Sensitivity (K/Jy): 8.5-11.5*
Measured System Temp (K): 34-40*
Native Polarization: Dual Linear**
Beam Size (at 1415 MHz): 3.1 x 3.5 arcmin*

*See calibration info below for a more accurate description of the telescope parameters!

**Note circular polarization is obtained from the receiver by using a hybrid. LCP on the sky comes down on the left-hand rack in the control room, which in the user's manual is referred to as pol A: at the correlator, it occupies the first half of the set of subcorrelators. For VLBI users, this is fed by convention to the BD tracks, unless the user makes some intervention of his own.

NOTE: This receiver has been replaced by a new L-wide receiver in February 2030.
Information on the new receiver can be found here

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Recent Events: The L_wide receiver was removed from the Gregorian at the end of January 2003, at the start of the campaign for realigning the zenith angle track (February 03). It is being replaced by the new L_band receiver. Some of its parts, such as the gain-tube cal unit, are now part of the new receiver.

The position of the feed horn was moved down 3.67 inches (towards the tertiary) on 22 Nov 02, to place its phase center at the focus. This results in a very much flatter gain adjustment curve, and a gain of about 11 K per Jy. The gain curves resulting from data taken between 21 Nov and 31st Dec, and the system performance from the limited number of tracks available links to Phil's page.

The compressor for the cooling lines to this receiver were refurbished in the fall-01; this is a regular, about two yearly occurrence to try to head off receiver warmups that can be attributed to compressor failures. In addition, this time a switch was also fitted to enable the compressors to be reset from the control room after a power dip, to try to minimize occasions on which the receiver warms up from this, more frequent, cause.

Large scale adjustments were made to the surface of the primary reflector between 20 Dec 2000 and 11 Jan 2001. Finer adjustments were made thereafter, with the last quadrant (southeast, which most affects the gain of northern sources) being the last to be finished in September. All gain curves this year (2001) therefore have their problems.

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Calibration & Beam Parameters:

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


The fitted variation of Tsys with za (in degrees) at 1415 MHz is:--

 Tsys(za) = 36.32 + 0.153*za + 0.17094*(za-14)^2 - 0.00741*(za-14)^3 K
where the last term is not significant

Currently, our best estimate for the dependence of the gain at 1415 MHz on za and az is:-

 Gain(za, az) = 10.85523 - 0.10291*za + 0.01343*(za-14)^2 - 0.00717*(za-14)^3

                          -0.20991*cos(az*3) -0.09803*sin(az*3)

In units of K per Jansky. The frequency dependence of the gain, and the process used to derive them are documented under the gain and system temperature button.

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Available Filters:

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electrically switchable filters on the wide-band L-band receiver

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  1. lbfb   1     none
  2. lbfb   2     1120-1220 MHz
  3. lbfb   3     1230-1470 MHz
  4. lbfb   4     1550-1820 MHz
  5. lbfb   5     1100-1800 MHz
  6. lbfb   6     1360-1470 MHz
  7. lbfb   7     none
  8. lbfb   8     1180-1280 MHz
  9. lbfb   9     none
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	Note: Filters can be moved between the narrow and wide-band L-band receivers	
              It is wise to check the disposition of the filter you want	
				
              lbfb # is the invocation to secure the desired filter	
              There is no stright through option with this receiver  

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Technical Information:

To find out the technical details about this receiver, just click on the appropriate icon in the engineering departments' receivers page (available here.) Some technical memos featuring the L_wide receiver are listed here.

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Receiver History:

Gene Lauria's description

The OMT has a number of resonances, which can greatly affect its performance, and the linearity of baselines obtained with it. In addition, the OMT is massive, and its thermal inertia causes the receiver to take about 40 hours to completely cool down to the desired operating temperatures.

Moreover it has never achieved a system temperature of better than about 34 K, whilst a Tsys of about 25 K was anticipated

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