[eagle] Re: Proposed Eagle Antenna Arrays

John B. Stephensen kd6ozh at comcast.net
Wed Feb 14 14:18:58 PST 2007


If the 70 cm antenna is too far from the center of the ground plane, it will skew the pattern and resut in excessive spin modulation at 30-60 degree offpointing angles. Ground stations near the horizon can experience up to 60 degrees offpointing at MA 32 and MA 224 so the ideal gain for the 2 m and 70 cm antennas seems to be 4-5 dBic. The 2 m antenna gain may be close to this number as the ground plane (satellite body) is so small. One possible 70 cm antenna is 2 orthogonal dipoles mounted 1/4-3/8 wavelength above the phased arrays. This might work well with square arrays of patches as the arrays can extend up to the dipole supports.

73,

John
KD6OZH

  ----- Original Message ----- 
  From: Louis McFadin 
  To: AMSAT Eagle 
  Sent: Wednesday, February 14, 2007 03:19 UTC
  Subject: [eagle] Proposed Eagle Antenna Arrays


  This is a repeat of the earlier e-mail.


  Here is a proposal for arranging the Eagle antennas that Stan Wood and I worked out today.
  By moving the 2M dipoles to the corners we have sufficient room for full sized elements over the ground plane. The 2M antennas should get about 8dB.


  Three L band patches in cavities should give us greater than 12 dB gain.
  By putting the S1,S2 and C band patches in hex shaped cups we maximize the available space. The cup arrays can be NC machined out of a solid blank and therefore attain precise control of the spacing. It may also serve as heat a radiating device. Each patch will be circular polarized and fed with a single feed from it's matching amplifier.


  The 70 CM Circular polarized patch should have around 6 dB gain.� We will look at getting more gain on 70 cm.� �Seven S1 patches will be mounted on top the 70CM patch. They should get about 15dB gain.


  Tom's S2 interferometric patches are included.


  Omni antennas similar to that used on P3D will be required on the opposite side of the spacecraft.


  There should also be room for the Sun Sensors on both sides of the spacecraft.












------------------------------------------------------------------------------





  Lou McFadin
  W5DID
  w5did at mac.com




  _______________________________________________
  Via the Eagle mailing list courtesy of AMSAT-NA
  Eagle at amsat.org
  http://amsat.org/mailman/listinfo/eagle



  Lou McFadin
  W5DID
  w5did at mac.com






------------------------------------------------------------------------------


  This is a repeat of the earlier e-mail.

  Here is a proposal for arranging the Eagle antennas that Stan Wood  
  and I worked out today.
  By moving the 2M dipoles to the corners we have sufficient room for  
  full sized elements over the ground plane. The 2M antennas should get  
  about 8dB.

  Three L band patches in cavities should give us greater than 12 dB gain.
  By putting the S1,S2 and C band patches in hex shaped cups we  
  maximize the available space. The cup arrays can be NC machined out  
  of a solid blank and therefore attain precise control of the spacing.  
  It may also serve as heat a radiating device. Each patch will be  
  circular polarized and fed with a single feed from it's matching  
  amplifier.

  The 70 CM Circular polarized patch should have around 6 dB gain.  We  
  will look at getting more gain on 70 cm.   Seven S1 patches will be  
  mounted on top the 70CM patch. They should get about 15dB gain.

  Tom's S2 interferometric patches are included.

  Omni antennas similar to that used on P3D will be required on the  
  opposite side of the spacecraft.

  There should also be room for the Sun Sensors on both sides of the  
  spacecraft.





  

  Lou McFadin
  W5DID
  w5did at mac.com


  _______________________________________________
  Via the Eagle mailing list courtesy of AMSAT-NA
  Eagle at amsat.org
  http://amsat.org/mailman/listinfo/eagle


  Lou McFadin
  W5DID
  w5did at mac.com





------------------------------------------------------------------------------


  _______________________________________________
  Via the Eagle mailing list courtesy of AMSAT-NA
  Eagle at amsat.org
  http://amsat.org/mailman/listinfo/eagle
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