[amsat-bb] Re: S band downlink on P3E
n4qwf1 at gmail.com
Fri Sep 8 10:37:44 PDT 2006
and a big hi, hi....Thanks Bob for telling it like it is.
On 9/8/06, Robert McGwier <rwmcgwier at comcast.net> wrote:
> Dave Guimont wrote:
> > 73, Dave wb6llo at amsat.org
> > Disagree: I learn....
> > Pulling for P3E...
> As are many of us. That said, The S transmitter is not the primary
> mode of P3E. The S band transmitter on P3E will be hooked to a dish.
> This dish will have a half power beam width which will limit the
> usefulness of the S band transmitter to those times of nadir pointing.
> The revelation of the results of our meeting, weeks before we could be
> ready to explain carefully that we are taking a system approach to the
> design of Eagle, is unfortunate. Not because the conclusions are made
> public but because there is no context for the decision making process.
> We cannot build an AO-40 class spacecraft. We do not have the
> personnel, the facilities, and we likely do not have sufficient talent
> that we can devote to such an enterprise. We have talent in this
> organization and around the world. But all of that talent leads a life
> outside of AMSAT. As an engineering manager for AMSAT it is my
> responsibility to make cold hard decisions based on personnel,
> calculation, advice, studies, equipment availability, the
> availability of launches that we can use and on and on.
> The organization overreacted to AO-40. It downsized Eagle
> considerably. It set a goal of no motor. It said "let's do digital"
> and "give them a whip antenna on two meters". It did not say this in a
> crass manner but those were absolutely the conclusions of the
> organization policies when captured into engineering possibilities.
> It has literally taken me 11 months to ALMOST right the ship. If the
> other people in the room will admit to it, I single handedly saved the
> linear transponders in our current designs by
> a) picking the receiver designer
> b) picking the transmitter designer
> c) choosing SDX as the overall concept for the linear transponder
> EVERYONE is on board. But do you think such things are done overnight?
> NO. They are done with leadership and not by whining. These decisions
> and their outcome led to a MUCH improved antenna system, power
> amplifier, and absolutely cutting edge efficiencies achievable for this
> transponder in our current plans. It went from 25 kHz fed to a quarter
> wave monopole on the back side of the spacecraft to serious antenna
> absolute eating valuable territory on the business side of the
> spacecraft and with bandwidth UP TO (but not necessarily) 100 kHz wide.
> The bandwidth will be determined by the TYPE of customers we wish to
> serve. We do not want to serve only those who can transmit 10 kW
> EIRP. We do want to support 1 KW EIRP SSB contacts. We also want to
> support a text messaging service that will require a shortened dipole on
> 70cm and 2m which will not be limited to APRS users.
> The goals stated by the AMSAT board of directors for its next HEO
> spacecraft design as a follow on to P3E (besides supporting P3E in the
> interim) included aiding those people who live in CC&R (covenant
> restricted) communities. It included aiding the first responders by
> giving them the ability to take a back pack full of equipment, set it
> up, and operate quickly. It stated that it wanted to produce a system
> of such satellites over a decade to be available 7/24.
> We have a concept, not a design, for a spacecraft. This concept is an
> "upsizing" of the near cubical Eagle. We are filling in the blanks on
> the concept in an attempt to present a design.
> The concepts we are building to include the ability to use the
> transponders on this spacecraft 365 days a year, in EVERY year the
> spacecraft is functional and to try and build a spacecraft that will be
> there and still usable when the third in the constellation is launched.
> Do you think this is easy? Of course not. It is easy to pitch mud when
> you are not responsible for an outcome.
> We are attempting to have NO bad seasons. We are attempting to have NO
> funny orbital problems. We are attempting to have the gain antennas
> solidly usable over 70% of the entire orbit. For these reasons and
> because of the desire to serve the CC&R customers, this meant we had to
> use microwaves to get sufficient gain on the antennas on the spacecraft
> and the ground. We fully understand that Dick Jansson, Drew, Dave,
> Tony, and others can give us anecdotes of how they can throw enough gain
> on their antenna system and make S band work for them. I believe they
> will not be happy with a 60 cm dish but will require a much larger dish
> to be happy and I am certain they would do it. I do not care. They are
> not who I am computing for. These are not the customers I am trying to
> serve. The customers I want to serve for the future of AMSAT cannot be
> served by a scratchy SSB signal and a (now) 4 foot dish. I have a
> mission directive from the board of directors you elected and voted for
> to serve these NEW customers. Those who will be here when the third
> satellite is launched. They will not be where Dave will be by then. I
> apologize for the crassness of this remark, but I am trying to make a
> point. I know Dave and have for nearly 30 years.. We are building for
> a guessed audience, with a guessed legal and RF environment, with a
> guessed ability to deliver 3 such payloads over the next 13 years.
> COLD HARD CALCULATION went into this analysis based on our best guesses
> and analyses. Given what we believe the environment will be We can
> only do this on microwaves and we can only do it digitally. PERIOD.
> End of story. God (as demonstrated through the mathematics of Claude
> Shannon) has dictated this outcome. We did not sit in a back room and
> decide what new toys we would throw your way to delight ourselves and to
> screw you (no more smoke and no more drink in there, we have grown old
> and boring) . To do it, I have to build a very complex antenna system
> that will take up most of the available area on the spacecraft for
> antennas. I cannot build a three axis stabilized spacecraft (I do not
> have the team or the money to do it), so I must do it with phased
> arrays. Matt Ettus has given us a great head start on this design and
> Tom Clark and John Stephensen have done great work on the antennas so
> far. We will test these antenna designs in the next twelve months
> thanks to a very generous antenna test range offer and design help by
> one of our members.
> The direction Jim and I gave our engineering team was that we cannot
> rely on this to work perfectly and meet every operational goal
> perfectly. STUFF HAPPENS. We are attempting to be ambitious but we
> absolutely must have a credible back up in case this system does not
> meet our expectations. We now have the upgraded Mode B transponder
> design which I believe will be the sweetest one flown since Oscar 7's
> Mode B. Fully equipped with the channelized AGC (Leila or Stella),
> generating HELAPS with modern technology and new fantastic amplifier
> I gave the argument to our engineering team that I have witnessed one
> experimental, new widget after another get built, flown, and then have
> its designers disheartened and dejected because it got "RUDAK'ed". It
> never really gets used or fully developed. It drifts into an inert lump
> that people mumble about when they are asked of their involvement. I
> insisted on enough spacecraft power generation to run BOTH the linear
> transponder and the digital transponder simultaneously and 365 days a
> year, EVERY year. This is the single most expensive decision we have
> made. We might spend 1/2 to 3/4 MILLION dollars on solar panels to
> accomplish this. I have insisted we have enough antenna space to make
> all of the antennas credible and based on calculation of the required
> antenna gains to close the links. Again, Claude Shannon has
> interpreted the natural laws and dictated the outcome. Cold hard
> calculation has gone into the needed solar generators, and the size of
> spacecraft required to support this.
> It will be about 4 feet across and look initially like a scaled DOWN
> AO-40 at launch if the concept becomes our design.
> We cannot deliver the quality of services we are demanding of ourselves
> if we fly all of the bands to be flown on P3E. We do not have the power
> or the antenna territory to meet our goals for these services.
> I have taken my direction from the board of directors of this
> organization. They made the vision statement. They can change it. You
> elected them.
> Several things will happen in October. We will install four
> directors. I may, or may not, be one of them. The board will vote
> whether or not to retain me as the VP Engineering. I have made almost
> NO ONE happy by slowing down those who drive me crazy with wanting to
> rush head long in a ready fire aim approach by demanding that we
> calculate our way to the vision statement to show the directors the
> consequences of the decision making processes. I have to tell you, I
> am damn proud of how much has been done in eleven months. Stuff got
> put on hold that aggravated many. We all make decisions about the way
> things have to go but I have done my best to aim us in a technically
> feasible direction. I do not have time to do all the everyone wants me
> to do. I will continue to do my best if I stay in the job.
> I offer the following. If the board votes to change their vision
> statement and not to build the spacecraft we are proposing, I will
> tender my resignation as VP Engineering since I will have failed to do
> the job they elected me to do which was to produce a usable concept to
> meet their vision. I am not interested in flying a carbon copy of P3E
> when I know it makes no sense whatsoever. I am 52 years old and one of
> the most active technical contributors in all of amateur radio. I will
> not waste my time doing what I know in my heart and my head is not in
> the best interests of amateur radio even if it is currently perceived to
> be for the good of the shrinking aging membership of AMSAT. It would
> be irresponsible of me not to attempt to aid the organization in
> addressing a new group of members while attempting to thread the needle
> of serving our current members. If elected to the board, and it changes
> direction, I will offer my seat to the first alternate. Vote for
> someone else if you do not want P3E built and you do not want the AMSAT
> vision statement attempted if you have not cast your vote.
> The story you have just been told should not have come out in this
> form. It was NEVER meant to be displayed in this form. The
> calculations were made at the first of July. They have undergone
> several iterations and were not really put in there latest form until
> August. In an attempt to get further interest from the microwave
> community, we made a decision to give a sneak peek to get some technical
> aid from RF specialists. This has backfired badly because we, the
> volunteers who have sacrificed countless hours on your behalf, have not
> had the time to put together a hundred pages of supporting documentation
> to tell the story in a coherent fashion so not only do we look like
> idiots, we have had to do things like waste 3.5 hours writing this
> silly note when I should have been asleep.
> Lastly. I have been accused here of being a con artist. I resent
> it. I don't need to con anyone. Frankly, I don't have to be here at
> all. I choose to be.
> 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
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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