Important information for users of the Lwide system June - December 2005

Lbw cal diode 1 failed on 22jul05. New diodes were installed on 23nov05. Check the cal history for more detail under the 23Nov05 and 23Feb06 spigots.

Important information for users of the Lwide system during 2003/2004

Since around may 2003, an error in the positions of the input cables to the 1320 filter has caused the polarisations to be reversed. Consequently, the calibration for data collected using the hipass 1320 and the hipass 1370 filters only will be mis-calibrated (i.e. by using the opposite polarisation calibration data). Observers for whom well-calibrated polarized data is necessary may need to re-reduce their data.

As of March 16, 2004, this problem is corrected

Observers using uncorrelated calibration data (i.e. not hcorcal or lcorcal) will not be significantly affected by this problem. To correct the problem, it is necessary to re-scale the data by the opposing pol.

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THE older (pre-Feb 2003) L-Wide receiver is no longer available.

Generally, the available configurations are consistent with the new L-Wide, with the following modifications:
The 1320 hipass has been moved from its old location in front of the filter bank, and is installed instead at position 7 (that had no previous connection). Filter 1 is now a NO connection location, so no signal will get through.
The current configuration has reversed the logic for the 1320 hipass filter. It is now possible to select any bandpass filter that is not in the 1320 hipass band. YOU SHOULD NOT select any bandpass filter that is IN the 1320 hipass band. i.e. It is NO longer ok to select lbfb 7 6 since the hipass and the 1360-1470 band overlap.

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2. Calibration & Beam Parameters:

Gain and Tsys

Cal Values

Beam Maps

Polarization

Misc. Info

• Gain and Tsys
  

  Most current Tsys here
  
  To see an up-to-date plot of Tsys, just type tsys on your terminal after logging into Arecibo's computer network.
  
  2003 Gain curves
  
  Plots of Latest Gain & Tsys curves
  
  
  Other L-Wide System performance parameters (eg earlier Tsys info, etc.) here
  
  

• Cal Values
  
click here




• Beam Maps
  
  lbw beammaps of 3C138 Feb 2007
  

  
  

• Polarization
  
  

  
  

• Misc. Info
  
  Other system performance data
  (eg sidelobes, beam efficiency, coma at a range of frequencies;
  gain, pointing errors, SEFD - regularly updated)
  

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3. RFI situation:

Monthly RFI information

Observations at L band for anything other than local HI usually requires co-ordination with other spectrum users to eliminate their RFI:

For observations around 1381 MHz an awareness of GPS L3 is necessary.
For observations in the 1222-1381 MHz range, coordination with the Punta Salinas Radar is essential
For observations in the 1610.6-1613.8 MHz range, protection from Iridium may be helpful.

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4. Recent Events:

Receiver log

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5. Receiver History:

The current L-wide receiver was installed on the telescope in February 2003, where it replaces the old L-wide receiver that had been in place since the upgrade. This receiver is a dual channel, cryogenic, native linear polarization receiver. The frequency range of this receiver is the same as the old: 1.15 - 1.73 GHz, but the horn, dewar design, OMT, amplifiers, and polarization module have all changed.

THE OLDER (PRE FEB-2003) L-WIDE IS NO LONGER AVAILABLE.

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6. Technical Info:

The feed is a new ring-loaded design by German Cortes of NAIC, Ithaca to replace the Ying-Kildal feed from the old L_Band wide. We expect the spillover contribution to be reduced compared to previous horn (-16 dB edge taper compared to -12 dB) The OMT (ortho-mode transducer) is a quad-ridge linear polarization design by NRAO Green Bank, who fabricated and tested the unit. This is the same type of OMT as the old L band wide, but has far fewer resonances (4 compared with 17 in the previous OMT, at 1265.5, 1449.38, 1609.15 & above 1720) and is a more compact design. The dewar design follows the GBT L Band receiver design. The cryogenic amplifiers are from NRAO Charlottesville. They are 3-stage PHEMT LNAs with noise temperatures of 2 - 4 K when cooled to 16K. These replace older Berkshire amplifiers with similar performance. The polarization box is another significant change. It was re-designed by R. Ganesan to allow for more reliable operation and lower noise contribution to Tsys. It is the module that changes the linear response to circular. It also includes a new band defining filter and a new post amplif ier. The band defining filter helps attenuate the RFI at 1000 - 1100 MHz and at 1850 - 2000 MHz. The filter bank module follows, and allows the user to select a combination of high pass filters and narrow bandpass filters. It has been slightly modified by adding some isolators to smooth out bandpass ripples. The block diagram. The IF system offers power level monitoring and adjustment, and a selection of IF and bandwidth combinations for the upconverted signal.

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7. Contact Info:

For further information on this receiver contact Murray Lewis at
blewis@naic.edu

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Last updated: Friday, 15-Feb-2008 13:10:33 AST
B. M. Lewis

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