Progress is being made on the backend wideband IF for my radiotelescope.  I purchased 
   the ABPM RF Meter from Downeast Microwave (designed by Paul Wade, W1GHZ) in part to 
   prototype a wideband RF detector using the AD8307 power detector IC.  This "chip" 
   made by Analog Devices is good up to 500-MHz so will work nice at the first IF of my 
   microwave converters.

   The 1420/144 radioastronomy convertor coupled with the RAS LNA provide about 60-dB of 
   gain ahead of the 144-MHz wideband IF (which I am calling the WBIF).  

   The WBIF consists of a VHF Filter followed by at least two IF amps (MAR-6 mmic) stages 
   each with 18-dB gain at 144-MHz to provide drive to the AD8307 over a range of -60 to 
   0 dBm.  It will tolerate up to +10 dBm.  I purchased the mmic amplifiers as kits from DEMI:
   Here is the schematic and pcb layout and a photo:
   









   When the 28.4 dBi gain of the 2.4 meter dish and is added and approx. 6 dB of line loss 
   subtracted, the total system gain for the 1420 MHz radiotelescope will be about 118 dB.
   A minimum detectable threshold of about -178 dBm is expected.

   The WBIF tested well at 144-MHz over this power range.  Bench measurements were 
   made using a calibrated signal generator to establish a power conversion chart.  
   Sun noise and Moon noise tests will be done soon.

   A prototype pcb has been built for the AD8307 with selectable RC 
   circuitry and a MAX186 12-bit A/D for input to the printer port of my computer which 
   will enable plotting of antenna noise measurements and observing celestial radio 
   sources.

   Below is a block diagram for the Wideband IF for Radio Astronomy.  
   Here is a link to the schematic diagram.
   





























   Photos of the prototype pc board and the complete WBIF Receiver, and sample chart using SkyPipe:
  
  


  





   This project is the subject of a paper for presentation to the 2006 SARA/SETI-League Conference.
   Here is a link to the Power Point presentation (683 Kb) given at the conference.  For the full article I 
   recommend you obtain a copy of the Proceeding from SARA.
   
   Please check back as add more content to this page!

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