[amsat-bb] Technical work, was Re: Re: Phase 4 versus Eagle

[Robert McGwier]

sco at sco-inc.com wrote:
> "WE" will be where our "host" is located and need to point from there 
> the best we can. I assume we will know this info before launch? So 
> whether or not we can aim for a certain spot is unknown until then.
> 
> At 02:59 PM 12/14/2007, you wrote:
>> Probably a good pointing spot would be where XM and Sirius Point their
>> antennas - just about on the Canadian Border close to Winnipeg- Manitoba
>> 73
>> Robin VE3FRH.
>>
>

We will know long in advance of the launch where our subsat point will
be.  Intelsat will then do station keeping. As we are selected for a
launch, we will be able to tell what the planned subsat will be.  We
will tell all of you what it is when our launch partner tells us we can.
 In addition, we will calculate where on the earth will be illuminated.
 We will calculate how much degradation there will be for users on the
limbs of the earth so they can size their antennas, etc. accordingly.
AMSAT is designing and will make available the terminals for the ACP.  I
remind that with this bird we no longer need rotors.


You will see in my upcoming journal columns that we have two flight
opportunities for SDX next year.  It was almost a third on a Cubesat but
that is the way things go some times.

We have purchased the necessary development to enable build of code for
the entire SDX and ACP in prototype form.  The SDX will contain the
"ultimate" HELAPS and this will be designed using the real modulator
which will be worked out with Marc Franco (N2UO).  We are expecting both
 efficiencies and linearity never thought possible a few years ago and
deliverable only with the DSP based HELAPS riding on board.

We have two Lyrtech boards which have TI DSP chips and FPGA to enable us
to do the work.  These boards produce and use IF and we can set them up
to operate on 10.7 MHz easily.  We are using rapid prototyping tools
that I get from work so we can quickly demonstrate this capability.

Howard has been continuously improving the SDX/Leila implementation and
I want to be able to start development on the HELAPS modulator and radar
pulse subtracter.

The same boards with the FPGA will enable us to build the wideband
digital modulator and polyphase filter bank demodulators for the ACP in
a reduced number of channels form to allow for easy algorithm
development.  Don't worry about all of this jargon for now.  It will all
be made clearer in my columns and demonstrations during the coming year.

We are only doing prototype work for now on the ACP and will only work
on the IF and baseband processors for the linear transponder because we
don't know the size of the linear transmitter yet.  Eagle will be ~50w
and Intelsat will be LOUD if we get the power we have requested and the
efficiencies we expect.  The ACP, even though it is all microwave,  will
be a hard limiting transmitter and very efficient.


Bob



-- 
AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
“An optimist may see a light where there is none, but why
must the pessimist always run to blow it out?” Descartes