[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: One satellite or many?



Bob,

My replies are lagging the reflector, so I missed this one on my last message.

It is clear to me that P4 will work very nicely 
at 1268 MHz and up.  There is a reason the 
commercial satellites use microwave frequencies 
(actually several).  For hams it means moving 
into unfamiliar territory, but I will say again 
that it will not be that difficult.  First there 
are a lot of you that already have accomplished 
2.4 GHz receive on AO-40.  Mode-LS would be a 
logical main band for P4.  Moving up in frequency 
makes sense for implementing the "apartment" or 
"emcomm" digital voice package.  Both space and 
ground antenna requirements are smaller.  The 
ground radio will be offered for emcomm so should 
also be a package available to the general ham 
population.  In time there should be competitive models available from mfrs.

Since P4 does not move in the sky, no rotors are 
needed.  The range is fixed.  You can design the 
ground station to match the path-loss.  No 
Doppler.  All sorts of digital PSK modes become 
usable since one does not have to deal with 
changing frequency/phase changes.  I would guess 
that polarization will be fixed as the Intelsat 
platform will be maintained at one location in 
orbit.  So no computer tracking or predicts.  Are 
you folks seeing how simple and nice P4 will be 
to set up and operate?  With passband 
transponders multiple QSO's will be possible with 
any kind of operating.  DX, ragchew, technical 
nets, traffic handling, mobile and portable 
comms, etc.   And of course emergency comms when needed.

Note most of this is my assumption on what will 
be done.  Details will be worked out with 
Intelsat that will determine the exact nature of what will be possible.

With SDX any new forms of modes may be uploaded and used.

Can you hear my excitement?  I pray we can make this fly!
73 Ed - KL7UW

At 08:53 PM 12/14/2007, Robert McGwier wrote:
>sco@sco-inc.com wrote: > a good hf station costs 
>more than many satellite stations. > V band and 
>U band are common low freq sat bands. what is 
>lower that those? > yes to work satellites the 
>operator needs to learn a lot more than > 
>working a FM repeater on a hilltop. > more than 
>one satellite at $6,000,000 each, how many do 
>you want to fund? > Eagle is not a tech 
>challenge, except perhaps the higher freq 
>digital part. > the host satellite decides where 
>our antennas go. they will likely > need to be 
>omni-directional to be of any use to use? > P4 
>sounds like the simplest and easiest to use ham 
>satellite that has > ever been thought about or 
>built. Both for the builders and the users. > > 
>Les W4SCO > Les: Let me state it clearly 
>again.  I promised I would and I will until it 
>gets through.  This audience cannot fund our 
>satellites, none of them that are proposed.  We 
>have attempted to get this audience to support 
>these activities and have failed.  There are 
>members of AMSAT who could write an $18,000,000 
>check for three payloads and they might wince, 
>but then would figure out a way to turn it into 
>an asset. They have chosen not to. Given this 
>state of affairs, these packages are all much 
>too expensive from design to orbit for "folks 
>who are working for a paycheck" like most of 
>us.  We have multimillionaires who read this 
>group who have given less than $100 in ten 
>years.  Go figure.  This situation, needing 
>millions and getting hundreds has been THE 
>SINGLE factor preventing anything from being 
>done.  Believe, don't believe, nothing will 
>change the facts.  Had we been able to, we would 
>have purchased a launch in 2000 and put up a P3 
>satellite and this conversation would not be 
>happening and we would not be aware of the P4 
>Lite opportunity.  It has nothing to do with 
>laziness,  stupidity, poor design, lack of 
>leadership, etc.  There simply is no easy way to 
>raise the money unless somebody else WANTS to 
>pay for it.  There are no free rides (so far as 
>the launch vehicle or payload companies are 
>concerned). We MIGHT be able to arrange a free 
>to us launch and the funding that will get 
>auxiliary payloads (piggy back) to orbit but we 
>are going to have to deliver a service to the 
>customer in return.  This is not at all unlike 
>designing building the structure that supported 
>PANAMSAT-1 during the AO-40 launch, or the 
>design work/construction that went into the ASAP 
>for Microsats, UOSAT's, etc. A satellite such as 
>AO-10,13,40, P3E, and Eagle are extremely 
>complex systems that happen to carry RF 
>packages. Eagle would need several 
>telescopes/cameras, attitude control systems, 
>rocket motors and fuel/oxidizer storage and flow 
>assemblies, solar panels that are horrendously 
>expensive, batteries that won't die in space, 
>etc. etc. With the P4 Lite approach,  we have 
>none of this at all.  We concentrate only on 
>delivering the services we and the members want 
>to deliver.  But again, the members will not 
>fund this package because of the large expense 
>of having Intelsat give us territory on their 
>bus and hundreds of watts for 15 years!   What 
>we need of members is to support the preliminary 
>design work so the launch authority will believe 
>we are credible enough to sign a deal with 
>us.  It is not that we are asleep. We did not 
>know this opportunity existed until last summer 
>and we have scrambled continuously since.  We 
>are waiting on their response to our request for 
>lots of details on all sorts of things. We need 
>member support to handle meetings, 
>prototypes,  overhead, laboratory building, and 
>much of the overhead of building the spacecraft 
>or payload.  I am not trying to discourage 
>members, I am trying to help you understand that 
>we have to do what we can get money for.  No 
>bucks, no Buck Rogers. The path loss from 
>Geostationary to the ground would imply you need 
>a 6 meter (> 19 foot) foot dish to use the omni 
>antennas on the digital and darn large on the 
>linear transponder.  We will not have omni 
>antennas as the primary antennas because we need 
>lots of gain on the spacecraft so we are putting 
>most of our radiated energy on the earth and not 
>calling ET and the universe. Should all of you 
>decide these packages and this thesis makes 
>sense, then support the design work irrespective 
>of whether I am on your Christmas list or not. 
>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 
>_______________________________________________ 
>Sent via AMSAT-BB@amsat.org. Opinions expressed 
>are those of the author. Not an AMSAT-NA member? 
>Join now to support the amateur satellite 
>program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

73,
Ed - KL7UW
======================================
  BP40IQ   50-MHz - 10-GHz   www.kl7uw.com
144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w
DUBUS Magazine USA Rep dubususa@hotmail.com
====================================== 


_______________________________________________
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb



AMSAT Top AMSAT Home