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
[email protected]


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


Lou McFadin
W5DID
[email protected]


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
[email protected]


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


Lou McFadin
W5DID
[email protected]


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