Robert McGwier wrote:
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.
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.
By "the command receiver" do you mean a fixed frequency demodulator output for the IHU3?
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 discussed some of these ideas with Eric, N7CL, at the TAPR meeting. Eric is very good at antenna system design, did S band stuff for us at MMS and does this sort of thing now for DoD.
Anyway, he suggested we consider Vivaldi's rather than patches. We used Vivaldi's on our trucks at S Band and they work well, are trivial to fabricate (a piece of PC board - I know, radiation, but it is the concept I am wanting us to consider). They are well behaved and have very little coupling to adjacent antennas. I'm not an antenna guy, but you might want to consider the Vivaldi and/or communicate with Eric.
Lyle
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 wb4gcs@amsat.org mailto:wb4gcs@amsat.org