Here is the drawing. The V antenna (3 dipoles) and the U antenna (crossed dipoles) are centered on the spin axis as the class 1 service is the most sensitive to spin modulation. The L, S1, S2 and C antennas are then arrayed around the U antenna. I used 4 patches for the L and S1 antennas as they may disrupt the U antenna pattern less than helices. Since an S2 array is 50% smaller than an S1 array, a 32 or 36 element array will fit nicely between the U and V antennas.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "Jim Sanford" [email protected] Cc: "'AMSAT Eagle'" [email protected] Sent: Monday, September 25, 2006 01:26 UTC Subject: [eagle] Re: Where we're heading for bands and services
Thank you Jim.
John, if you would, please transmit your antenna concept drawing to the group. I really like it.
When I answered Rick's proposal for an L band uplink in our decision meeting, I suggested that we do it with a 200 kHz limit and that final bandwidth is to be determined by calculation. I suggest we base the IF for the L band input to the ACP on QSD. It is a high dynamic range, low power mixer. We can digitize that with audio A/D's running pretty low power and send I/Q to the ACP/DSP. This will give Region 1 a few uplinks to the ACP.
On L band we need the SDX pick off, the ACP pick off, and the command receiver pick off using a single antenna and any LNA.
My first reaction to John's subsequent block diagram was that the switching arrangement is complex and I did not understand the need for some of the lines in it.
S2/C is a technical win over S1/C because of the smaller antenna area on the spacecraft (18 dBi fixed design) and giving us the ability to separate the two antennas. John and I discussed the spin doppler caused by the offset patches. It will be insignificant. The noise floor at the satellite on 3.4 should be considerably less than S2 and with the "region 1" input, where we should require Class 3 EIRP or thereabouts, allows them to use the facility.
I have really enjoyed all of the debate, design meetings, and ideas but I like coming to a place where we can begin to design hardware and the services. We really do need a launch to focus on. Those efforts are ongoing and probably will be for a while.
Bob N4HY
Jim Sanford wrote:
Team:
The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering (N4HY) and I met (electronically) to discuss the Eagle payload complement.
We have decided the following should be our recommendation to the board of directors of AMSAT for their ratification. This is what will be presented to the BoD:
- Services to be provided, as defined at the San Diego meeting et seq: Class 0 is linear transponder users Class 1 is SMS text message service users Class 2 is weak signal voice grade digital channel Class 3 is strong signal, large antenna, higher bandwidth signal
(think compressed full motion video)
--- snip --
Very 73, Jim [email protected] mailto:[email protected]
-- AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman "You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat." - Einstein
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