The designer of the code to demodulate class 1 uplinks in the SDX needs to determine whether spin modulation can be compensated for. The carrier tracking loop bandwidth may be close enough to the satellite spin rate that it can't be eliminated. I'm not sure how well open loop compensation would work as the phase pertubation will vary with the arrival angle of the signal and this could vary by as much as 30 degrees at MA32 and MA224.
 
73,
 
John
KD6OZH
----- Original Message -----
From: Jim Sanford
To: Louis McFadin
Cc: AMSAT Eagle
Sent: Wednesday, September 27, 2006 01:30 UTC
Subject: [eagle] Re: Proposed Eagle Antenna Arrays

Team:
I've enjoyed monitoring this stream of conciousness discussion. 

Question:  Is it time to take a design and start formally vetting it? 

My sense is that we ARE close to time to develop a formal proposal and do at least a preliminary peer review.  If you strongly object, please say so now.  I will listen.

I propose the following:
1.  Lou and Stan resolve the unresolved issues Lou mentions in his note.
2.  Lou and Stan publish final draft design and design report stating specifications and any notes, design assumptions, etc.  This design report to contain enough details that peer reviewers can load into the model of their choosing and model the design as part of the peer review.
3.  Peer review committee start reviewing.  Committee consists of:  John Stephenson, Tom Clark, Bob McGwier, Rick Hambly, and myself.  Open to suggestion on additional reviewers.  (Paul Wade??)  Lou & Stan are designers, not reviewers, so they will participate in the discussions in that role.

Thoughts??

My first comment:  I note that none of the arrays, except 2m, are symmetrical (in themselves) about the spin axis.  I request that the design report discuss spin modulation and peer reviewers assess same.

Time frame:  I'd expect it to take a month for Lou & Stan to finalize design.  With Symposium in the middle, make it six weeks.  Given potential modelling involved, I'd expect the first round of peer review comments to take 4 to 6 weeks to develop, and 2 to 3 weeks to develop responses or corrections.

It is fair game for a reviewer to suggest a completely different design (with rationale) but let's start here.

Your thoughts??

Thanks & 73,
Jim
wb4gcs@amsat.org


Louis McFadin wrote:
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@mac.com



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

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