GBT Scientific Working Group Meeting of October 18, 1994 
 
      4 PM EDT

We are trying a new phone conferencing system and will give it one more try.
If it seems that you are not being heard, please hang up and dial again.

DIAL  804-296-7082  anytime after 3:55 PM EDT and it should work.



                   
                AGENDA

  I.  Update on the Project  (new schedule)

 II.  Spectrometer News 

III.  K Band receiver on the 140 foot (see attached information)

 IV.  Summary of GBT Advisory Committee meeting

  V.  Further GBT tests on the 140 foot

 VI.  7-feed receiver to move to the GBT?


If there are any topics you would like discussed please contact me:
jlockman@nrao.edu
       



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	There are several new items on the World Wide Web that give up to date
information on the GBT spectrometer and receivers.  You can get to them
throught the GBT entry on the NRAO home page:  info.gb.nrao.edu


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	GBT K BAND RECEIVER ON THE 140 FOOT TELESCOPE


We have recently tested on the 140-ft telescope the 18-22 GHz HFET
receiver that has replaced the maser receiver and which will eventually
be used on the GBT.  The receiver performed extremely well.  Although
the weather during the tests was far from ideal, I predict that the
zenith system temperatures  under good winter weather conditions will
be about 55 K at 22.2 GHz and 40 K at 20 GHz.  These system
temperatures are about as good as what the maser receiver used to
provide and will be much better when the receiver is used on the GBT
due to the lower contribution to the system temperature on the GBT from
spillover and scattering.  

The receiver requires no tuning (other than a change of LO)  between 
frequencies.  The instantaneous frequency coverage, now limited by 
the 140 foot IF system to about 450 MHz, will be the entire range 
of sky frequencies on the GBT.   The second part of the GBT K band 
receiver system covering 22 to 26 GHz is also mounted on the 140 foot 
but has not yet been tested.  Because of mechanical limitations on 
the 140 foot, a change between the 18-22 GHz and 22-26 GHz bands now 
requires a few hours, but on the GBT both bands will be available 
simultaneously.


						Ronald J. Maddalena