Hi Bob,
Your response alluded to a desire by many to "duplicate P3E." I didn't read that into the responses. I seriously don't think that's a real issue for discussion.
First the "sunshine" comments.
I "seriously" appreciate the efforts that you and your team have put in, to get us this far in the Eagle development and look forward to a satellite that will have capabilities for many communicators.
Secondly, now lets focus on the "not so sunshiny" issue being discussed - a 2.4 GHz downlink.
I am involved with UWB (Ultra Wide Band) design and deployment. I won't go into UWB details (except to say it will operate somewhere above 3 to 4 GHz with a very, very wide instantaneous bandwidth) but my marketing guys say it will offer the wireless systems of the near future. They may be wrong but I think they're on to something. Why? Simple facts bear them out.
Lets just take the cordless phone history. We once had 49 MHz cordless phones. They're now gone. Same with 900 MHz phones. Currently 2.4 Ghz is the cordless phone "de jur." But what's right around the corner?
Fact (1): You could just look at the new 5.8 GHz product offerings by Hittite, Sirenza, Freescale and whole lot more to see where they're placing their design emphasis but today was shopping day so I thought I'd do some simple consumer research, if you will.
My results:
Sam Club offered 5 cordless phones - all the 5.8 Ghz variety (i.e. - no 2.4 GHz phones)
Costco offered 5 cordless phones - 4 were the 5.8 GHz variety and 1 was at 2.4 GHz.
Best Buy - 3 were 5.8 GHz, 2 were 2.4 GHz.
The point: Our electronics industry is bent on creating obsolete throw away products to fuel the economic engines (Being in the industry I can appreciate that). Already the move is on for the WiFi applications at 5.8 GHz (including the high power - 1 watt - 5.8 Ghz applications).
So in 3 years when Eagel is launched I believe it is very possible that the 2.4 GHz interference issue may have gotten better with the clearly predictable consumer industry transitions up the microwave spectrum and at that time maybe we should be concerned with the vulnerability of the proposed 5.8 GHz satellite links???? I believe this argument might be as valid and your groups arguments.
I would also ask - if the inference problem at 2.4 GHz is as severe as you repeatedly state - how come the cordless phones and WiFi systems don't drown themselves out an collapse with their own sea of mutual interference?
What I have been reading is a preponderance of AO-40 2.4 GHz operators who have experienced some interference but it didn't destroy their use of the capability. So what's so new about amateurs working with some QRM.
So instead of just bitching I'm offering some alternatives that could "sooth the masses!"
Proposal): Put in place a parallel "2.4 GHz team" to design and build a 2.4 GHz downlink capability in the off chance your dire predictions could be wrong and room and current can be budgeted for it. Sure - problems will abound but its a proactive activity that is worth considering.
Proposal (2): As has been suggested here, lets put as much energy in getting our satellite allocations modified as we have used to argue 2.4 GHz. While it might be too late, WRC-2007 is around the corner and perhaps we can still lobby the FCC's Informal Working Group 4 to help us out.
I would offer my help with Proposal (1) and I'm sure there are really qualified members would could pursue Proposal (2)
Respectfully (and I mean that)
Bill - N6GHz AMSAT #21049
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org]On Behalf Of Robert McGwier Sent: Friday, September 08, 2006 3:19 AM To: Dave Guimont Cc: amsat-bb@amsat.org Subject: [amsat-bb] Re: S band downlink on P3E
Dave Guimont wrote:
73, Dave wb6llo@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 components.
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.
Bob N4HY
-- 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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